From 6af344c28f39839cefc22921ffbdee71ed551a67 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Thu, 7 Jan 2021 17:04:52 +0300
Subject: [PATCH 01/18] null safety

---
 benchmark/shortest_path_benchmark.dart       |  4 +--
 example/crawl_async_example.dart             | 25 +++++++------
 example/example.dart                         |  2 +-
 lib/src/crawl_async.dart                     |  4 +--
 lib/src/shortest_path.dart                   | 32 ++++++++---------
 lib/src/strongly_connected_components.dart   | 22 ++++++++----
 pubspec.yaml                                 | 13 ++++---
 test/crawl_async_test.dart                   |  7 ++--
 test/shortest_path_test.dart                 | 37 +++++++-------------
 test/strongly_connected_components_test.dart | 10 +++---
 test/utils/graph.dart                        | 18 +++++-----
 test/utils/utils.dart                        |  4 +--
 12 files changed, 88 insertions(+), 90 deletions(-)

diff --git a/benchmark/shortest_path_benchmark.dart b/benchmark/shortest_path_benchmark.dart
index 813c18b..099468a 100644
--- a/benchmark/shortest_path_benchmark.dart
+++ b/benchmark/shortest_path_benchmark.dart
@@ -21,7 +21,7 @@ void main() {
     }
   }
 
-  int minTicks;
+  int? minTicks;
   var maxIteration = 0;
 
   final testOutput =
@@ -34,7 +34,7 @@ void main() {
     watch
       ..reset()
       ..start();
-    final length = shortestPath(0, size - 1, (e) => graph[e] ?? []).length;
+    final length = shortestPath(0, size - 1, (e) => graph[e] ?? [])?.length;
     watch.stop();
     assert(length == 4, '$length');
 
diff --git a/example/crawl_async_example.dart b/example/crawl_async_example.dart
index ce4c3e3..35a63a7 100644
--- a/example/crawl_async_example.dart
+++ b/example/crawl_async_example.dart
@@ -26,9 +26,9 @@ Future<Null> main() async {
   print(allImports.map((s) => s.uri).toList());
 }
 
-AnalysisContext _analysisContext;
+AnalysisContext? _analysisContext;
 
-Future<AnalysisContext> get analysisContext async {
+Future<AnalysisContext?> get analysisContext async {
   if (_analysisContext == null) {
     var libUri = Uri.parse('package:graphs/');
     var libPath = await pathForUri(libUri);
@@ -39,25 +39,28 @@ Future<AnalysisContext> get analysisContext async {
       throw StateError('Expected to find exactly one context root, got $roots');
     }
 
-    _analysisContext = ContextBuilder().createContext(contextRoot: roots[0]);
+    final analysisContext =
+        ContextBuilder().createContext(contextRoot: roots[0]);
+    _analysisContext = analysisContext;
+    return analysisContext;
   }
 
-  return _analysisContext;
+  return null;
 }
 
-Future<Iterable<Uri>> findImports(Uri from, Source source) async {
-  return source.unit.directives
+Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
+  return source.unit?.directives
       .whereType<UriBasedDirective>()
       .map((d) => d.uri.stringValue)
       .where((uri) => !uri.startsWith('dart:'))
       .map((import) => resolveImport(import, from));
 }
 
-Future<CompilationUnit> parseUri(Uri uri) async {
+Future<CompilationUnit?> parseUri(Uri uri) async {
   var path = await pathForUri(uri);
-  var analysisSession = (await analysisContext).currentSession;
-  var parseResult = analysisSession.getParsedUnit(path);
-  return parseResult.unit;
+  var analysisSession = (await analysisContext)?.currentSession;
+  var parseResult = analysisSession?.getParsedUnit(path);
+  return parseResult?.unit;
 }
 
 Future<String> pathForUri(Uri uri) async {
@@ -81,7 +84,7 @@ Uri resolveImport(String import, Uri from) {
 
 class Source {
   final Uri uri;
-  final CompilationUnit unit;
+  final CompilationUnit? unit;
 
   Source(this.uri, this.unit);
 }
diff --git a/example/example.dart b/example/example.dart
index 47aca61..2fbb8e1 100644
--- a/example/example.dart
+++ b/example/example.dart
@@ -41,7 +41,7 @@ void main() {
   });
 
   var components = stronglyConnectedComponents<Node>(
-      graph.nodes.keys, (node) => graph.nodes[node]);
+      graph.nodes.keys, (node) => graph.nodes[node] ?? []);
 
   print(components);
 }
diff --git a/lib/src/crawl_async.dart b/lib/src/crawl_async.dart
index 2cf0f54..5a74170 100644
--- a/lib/src/crawl_async.dart
+++ b/lib/src/crawl_async.dart
@@ -34,7 +34,7 @@ final _empty = Future<Null>.value(null);
 /// have not completed. If the [edges] callback needs to be limited or throttled
 /// that must be done by wrapping it before calling [crawlAsync].
 Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V> Function(K) readNode,
-    FutureOr<Iterable<K>> Function(K, V) edges) {
+    FutureOr<Iterable<K>?> Function(K, V) edges) {
   final crawl = _CrawlAsync(roots, readNode, edges)..run();
   return crawl.result.stream;
 }
@@ -43,7 +43,7 @@ class _CrawlAsync<K, V> {
   final result = StreamController<V>();
 
   final FutureOr<V> Function(K) readNode;
-  final FutureOr<Iterable<K>> Function(K, V) edges;
+  final FutureOr<Iterable<K>?> Function(K, V) edges;
   final Iterable<K> roots;
 
   final _seen = HashSet<K>();
diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index f0fd598..bb16b5c 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -24,12 +24,12 @@ import 'dart:collection';
 ///
 /// If you supply one of [equals] or [hashCode], you should generally also to
 /// supply the other.
-List<T> shortestPath<T>(
+List<T>? shortestPath<T>(
   T start,
   T target,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(
       start,
@@ -61,8 +61,8 @@ List<T> shortestPath<T>(
 Map<T, List<T>> shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(
       start,
@@ -74,29 +74,29 @@ Map<T, List<T>> shortestPaths<T>(
 Map<T, List<T>> _shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
-  T target,
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  T? target,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) {
   assert(start != null, '`start` cannot be null');
   assert(edges != null, '`edges` cannot be null');
 
   final distances = HashMap<T, List<T>>(equals: equals, hashCode: hashCode);
-  distances[start] = List(0);
+  distances[start] = [];
 
   equals ??= _defaultEquals;
-  if (equals(start, target)) {
+  if (equals.call(start, target)) {
     return distances;
   }
 
   final toVisit = ListQueue<T>()..add(start);
 
-  List<T> bestOption;
+  List<T>? bestOption;
 
   while (toVisit.isNotEmpty) {
     final current = toVisit.removeFirst();
     final currentPath = distances[current];
-    final currentPathLength = currentPath.length;
+    final currentPathLength = currentPath?.length ?? 0;
 
     if (bestOption != null && (currentPathLength + 1) >= bestOption.length) {
       // Skip any existing `toVisit` items that have no chance of being
@@ -111,12 +111,12 @@ Map<T, List<T>> _shortestPaths<T>(
       assert(existingPath == null ||
           existingPath.length <= (currentPathLength + 1));
 
-      if (existingPath == null) {
-        final newOption = List<T>(currentPathLength + 1)
+      if (existingPath == null && currentPath != null) {
+        final newOption = List<T>.filled(currentPathLength + 1, edge)
           ..setRange(0, currentPathLength, currentPath)
           ..[currentPathLength] = edge;
 
-        if (equals(edge, target)) {
+        if (target != null && equals(edge, target)) {
           assert(bestOption == null || bestOption.length > newOption.length);
           bestOption = newOption;
         }
@@ -134,4 +134,4 @@ Map<T, List<T>> _shortestPaths<T>(
   return distances;
 }
 
-bool _defaultEquals(Object a, Object b) => a == b;
+bool _defaultEquals<T>(T a, T b) => a == b;
diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index 26018b9..8648957 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -32,8 +32,8 @@ import 'dart:math' show min;
 List<List<T>> stronglyConnectedComponents<T>(
   Iterable<T> nodes,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) {
   final result = <List<T>>[];
   final lowLinks = HashMap<T, int>(equals: equals, hashCode: hashCode);
@@ -52,12 +52,20 @@ List<List<T>> stronglyConnectedComponents<T>(
     lastVisited.addLast(node);
     onStack.add(node);
     // ignore: omit_local_variable_types
-    for (final T next in edges(node) ?? const []) {
+    for (final T next in edges(node)) {
       if (!indexes.containsKey(next)) {
         strongConnect(next);
-        lowLinks[node] = min(lowLinks[node], lowLinks[next]);
+        final n = lowLinks[node];
+        final x = lowLinks[next];
+        if (n != null && x != null) {
+          lowLinks[node] = min(n, x);
+        }
       } else if (onStack.contains(next)) {
-        lowLinks[node] = min(lowLinks[node], indexes[next]);
+        final n = lowLinks[node];
+        final x = indexes[next];
+        if (n != null && x != null) {
+          lowLinks[node] = min(n, x);
+        }
       }
     }
     if (lowLinks[node] == indexes[node]) {
@@ -67,7 +75,7 @@ List<List<T>> stronglyConnectedComponents<T>(
         next = lastVisited.removeLast();
         onStack.remove(next);
         component.add(next);
-      } while (!equals(next, node));
+      } while (equals?.call(next, node) == false);
       result.add(component);
     }
   }
@@ -78,4 +86,4 @@ List<List<T>> stronglyConnectedComponents<T>(
   return result;
 }
 
-bool _defaultEquals(Object a, Object b) => a == b;
+bool _defaultEquals<T>(T a, T b) => a == b;
diff --git a/pubspec.yaml b/pubspec.yaml
index cf0075b..6bc2896 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,16 +1,15 @@
 name: graphs
-version: 0.2.1-dev
+version: 0.3.0-nullsafety.0
 description: Graph algorithms that operate on graphs in any representation
 homepage: https://github.com/dart-lang/graphs
 
 environment:
-  sdk: '>=2.2.0 <3.0.0'
+  sdk: '>=2.12.0-0 <3.0.0'
 
 dev_dependencies:
-  pedantic: ^1.3.0
-  test: ^1.5.1
+  pedantic: ^1.10.0-nullsafety.3
+  test: ^1.16.0-nullsafety.13
 
   # For examples
-  analyzer: '>=0.35.0 <0.41.0'
-  path: ^1.1.0
-  pool: ^1.3.0
+  path: ^1.8.0-nullsafety.3
+  pool: ^1.5.0-nullsafety.3
diff --git a/test/crawl_async_test.dart b/test/crawl_async_test.dart
index 4a0011b..7481264 100644
--- a/test/crawl_async_test.dart
+++ b/test/crawl_async_test.dart
@@ -2,16 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:test/test.dart';
-
 import 'package:graphs/graphs.dart';
+import 'package:test/test.dart';
 
 import 'utils/graph.dart';
 
 void main() {
   group('asyncCrawl', () {
-    Future<List<String>> crawl(
-        Map<String, List<String>> g, Iterable<String> roots) {
+    Future<List<String?>> crawl(
+        Map<String, List<String>?> g, Iterable<String> roots) {
       var graph = AsyncGraph(g);
       return crawlAsync(roots, graph.readNode, graph.edges).toList();
     }
diff --git a/test/shortest_path_test.dart b/test/shortest_path_test.dart
index 3e38067..f787ce3 100644
--- a/test/shortest_path_test.dart
+++ b/test/shortest_path_test.dart
@@ -24,10 +24,10 @@ void main() {
     '6': ['7'],
   };
 
-  List<String> getValues(String key) => graph[key] ?? [];
+  List<String?> getValues(String? key) => graph[key] ?? [];
 
   List<X> getXValues(X key) =>
-      graph[key.value]?.map((v) => X(v))?.toList() ?? [];
+      graph[key.value]?.map((v) => X(v)).toList() ?? [];
 
   test('null `start` throws AssertionError', () {
     expect(() => shortestPath(null, '1', getValues),
@@ -36,30 +36,17 @@ void main() {
         _throwsAssertionError('`start` cannot be null'));
   });
 
-  test('null `edges` throws AssertionError', () {
-    expect(() => shortestPath(1, 1, null),
-        _throwsAssertionError('`edges` cannot be null'));
-    expect(() => shortestPaths(1, null),
-        _throwsAssertionError('`edges` cannot be null'));
-  });
-
   test('null return value from `edges` throws', () {
-    expect(shortestPath(1, 1, (input) => null), <dynamic>[],
-        reason: 'self target short-circuits');
     expect(shortestPath(1, 1, (input) => [null]), <dynamic>[],
         reason: 'self target short-circuits');
 
-    expect(() => shortestPath(1, 2, (input) => null), throwsNoSuchMethodError);
-
-    expect(() => shortestPaths(1, (input) => null), throwsNoSuchMethodError);
-
     expect(() => shortestPath(1, 2, (input) => [null]),
         _throwsAssertionError('`edges` cannot return null values.'));
     expect(() => shortestPaths(1, (input) => [null]),
         _throwsAssertionError('`edges` cannot return null values.'));
   });
 
-  void _singlePathTest(String from, String to, List<String> expected) {
+  void _singlePathTest(String from, String? to, List<String>? expected) {
     test('$from -> $to should be $expected (mapped)', () {
       expect(
           shortestPath<X>(X(from), X(to), getXValues,
@@ -127,7 +114,7 @@ void main() {
     final size = 1000;
     final graph = HashMap<int, List<int>>();
 
-    List<int> resultForGraph() =>
+    List<int>? resultForGraph() =>
         shortestPath<int>(0, size - 1, (e) => graph[e] ?? const []);
 
     void addRandomEdge() {
@@ -139,7 +126,7 @@ void main() {
       }
     }
 
-    List<int> result;
+    List<int>? result;
 
     // Add edges until there is a shortest path between `0` and `size - 1`
     do {
@@ -156,10 +143,10 @@ void main() {
     do {
       expect(++count, lessThan(size * 5), reason: 'This loop should finish.');
       addRandomEdge();
-      final previousResultLength = result.length;
+      final previousResultLength = result?.length;
       result = resultForGraph();
       expect(result, hasLength(lessThanOrEqualTo(previousResultLength)));
-    } while (result.length > 2);
+    } while ((result?.length ?? 0) > 2);
 
     expect(result, [275, 999]);
 
@@ -173,11 +160,13 @@ void main() {
       final randomKey = graph.keys.elementAt(_rnd.nextInt(graph.length));
       final list = graph[randomKey];
       expect(list, isNotEmpty);
-      list.removeAt(_rnd.nextInt(list.length));
-      if (list.isEmpty) {
-        graph.remove(randomKey);
+      if (list != null) {
+        list.removeAt(_rnd.nextInt(list.length));
+        if (list.isEmpty) {
+          graph.remove(randomKey);
+        }
       }
-      final previousResultLength = result.length;
+      final previousResultLength = result?.length;
       result = resultForGraph();
       if (result != null) {
         expect(result, hasLength(greaterThanOrEqualTo(previousResultLength)));
diff --git a/test/strongly_connected_components_test.dart b/test/strongly_connected_components_test.dart
index 6c3968d..11f36d1 100644
--- a/test/strongly_connected_components_test.dart
+++ b/test/strongly_connected_components_test.dart
@@ -12,8 +12,8 @@ void main() {
   group('strongly connected components', () {
     /// Run [stronglyConnectedComponents] on [g].
     List<List<String>> components(
-      Map<String, List<String>> g, {
-      Iterable<String> startNodes,
+      Map<String, List<String>?> g, {
+      Iterable<String>? startNodes,
     }) {
       final graph = Graph(g);
       return stronglyConnectedComponents(
@@ -147,9 +147,9 @@ void main() {
 
   group('custom hashCode and equals', () {
     /// Run [stronglyConnectedComponents] on [g].
-    List<List<String>> components(
-      Map<String, List<String>> g, {
-      Iterable<String> startNodes,
+    List<List<String?>> components(
+      Map<String, List<String>?> g, {
+      Iterable<String?>? startNodes,
     }) {
       final graph = BadGraph(g);
 
diff --git a/test/utils/graph.dart b/test/utils/graph.dart
index f14efe0..96200a2 100644
--- a/test/utils/graph.dart
+++ b/test/utils/graph.dart
@@ -8,11 +8,11 @@ import 'utils.dart';
 
 /// A representation of a Graph since none is specified in `lib/`.
 class Graph {
-  final Map<String, List<String>> _graph;
+  final Map<String, List<String>?> _graph;
 
   Graph(this._graph);
 
-  List<String> edges(String node) => _graph[node];
+  List<String> edges(String node) => _graph[node] ?? [];
 
   Iterable<String> get allNodes => _graph.keys;
 }
@@ -20,12 +20,12 @@ class Graph {
 class BadGraph {
   final Map<X, List<X>> _graph;
 
-  BadGraph(Map<String, List<String>> values)
+  BadGraph(Map<String, List<String>?> values)
       : _graph = LinkedHashMap(equals: xEquals, hashCode: xHashCode)
-          ..addEntries(values.entries.map(
-              (e) => MapEntry(X(e.key), e?.value?.map((v) => X(v))?.toList())));
+          ..addEntries(values.entries.map((e) =>
+              MapEntry(X(e.key), e.value?.map((v) => X(v)).toList() ?? [])));
 
-  List<X> edges(X node) => _graph[node];
+  List<X> edges(X node) => _graph[node] ?? [];
 
   Iterable<X> get allNodes => _graph.keys;
 }
@@ -33,12 +33,12 @@ class BadGraph {
 /// A representation of a Graph where keys can asynchronously be resolved to
 /// real values or to edges.
 class AsyncGraph {
-  final Map<String, List<String>> graph;
+  final Map<String, List<String>?> graph;
 
   AsyncGraph(this.graph);
 
-  Future<String> readNode(String node) async =>
+  Future<String?> readNode(String node) async =>
       graph.containsKey(node) ? node : null;
 
-  Future<Iterable<String>> edges(String key, String node) async => graph[key];
+  Future<Iterable<String>?> edges(String key, String? node) async => graph[key];
 }
diff --git a/test/utils/utils.dart b/test/utils/utils.dart
index f4ed52b..981bad2 100644
--- a/test/utils/utils.dart
+++ b/test/utils/utils.dart
@@ -2,12 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-bool xEquals(X a, X b) => a?.value == b?.value;
+bool xEquals(X? a, X? b) => a?.value == b?.value;
 
 int xHashCode(X a) => a.value.hashCode;
 
 class X {
-  final String value;
+  final String? value;
 
   X(this.value);
 

From 1a3dbe6434906c3229aa42ec0180717938e8061d Mon Sep 17 00:00:00 2001
From: Kevin Moore <kevmoo@users.noreply.github.com>
Date: Thu, 21 Jan 2021 00:31:15 -0800
Subject: [PATCH 02/18] Migrate to GitHub Actions (#53)

* Fix List deprecation
* Support old sdks
---
 .github/workflows/ci.yml   | 64 ++++++++++++++++++++++++++++++++++++++
 .travis.yml                | 22 -------------
 lib/src/shortest_path.dart |  9 +++---
 3 files changed, 69 insertions(+), 26 deletions(-)
 create mode 100644 .github/workflows/ci.yml
 delete mode 100644 .travis.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..687adbd
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,64 @@
+name: CI
+
+on:
+  # Run on PRs and pushes to the default branch.
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  schedule:
+    - cron: "0 0 * * 0"
+
+env:
+  PUB_ENVIRONMENT: bot.github
+
+jobs:
+  # Check code formatting and static analysis on a single OS (linux)
+  # against Dart dev.
+  analyze:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sdk: [dev]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v0.3
+        with:
+          sdk: ${{ matrix.sdk }}
+      - id: install
+        name: Install dependencies
+        run: dart pub get
+      - name: Check formatting
+        run: dart format --output=none --set-exit-if-changed .
+        if: always() && steps.install.outcome == 'success'
+      - name: Analyze code
+        run: dart analyze --fatal-infos
+        if: always() && steps.install.outcome == 'success'
+
+  # Run tests on a matrix consisting of two dimensions:
+  # 1. OS: ubuntu-latest, (macos-latest, windows-latest)
+  # 2. release channel: dev
+  test:
+    needs: analyze
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        # Add macos-latest and/or windows-latest if relevant for this package.
+        os: [ubuntu-latest]
+        sdk: [2.3.0, dev]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v0.3
+        with:
+          sdk: ${{ matrix.sdk }}
+      - id: install
+        name: Install dependencies
+        run: pub get
+      - name: Run VM tests
+        run: pub run test --platform vm
+        if: always() && steps.install.outcome == 'success'
+      - name: Run Chrome tests
+        run: pub run test --platform chrome
+        if: always() && steps.install.outcome == 'success'
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 44cbea1..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,22 +0,0 @@
-language: dart
-
-dart:
-  - dev
-  - 2.2.0
-
-dart_task:
-  - test
-  - test -p chrome,firefox
-  - dartanalyzer: --fatal-infos --fatal-warnings .
-
-matrix:
-  include:
-    - dart: dev
-      dart_task: dartfmt
-
-branches:
-  only: [master]
-
-cache:
-  directories:
-    - $HOME/.pub-cache
diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index bb16b5c..3905443 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -82,7 +82,7 @@ Map<T, List<T>> _shortestPaths<T>(
   assert(edges != null, '`edges` cannot be null');
 
   final distances = HashMap<T, List<T>>(equals: equals, hashCode: hashCode);
-  distances[start] = [];
+  distances[start] = const [];
 
   equals ??= _defaultEquals;
   if (equals.call(start, target)) {
@@ -112,9 +112,10 @@ Map<T, List<T>> _shortestPaths<T>(
           existingPath.length <= (currentPathLength + 1));
 
       if (existingPath == null && currentPath != null) {
-        final newOption = List<T>.filled(currentPathLength + 1, edge)
-          ..setRange(0, currentPathLength, currentPath)
-          ..[currentPathLength] = edge;
+        final newOption = [
+          ...currentPath,
+          edge,
+        ];
 
         if (target != null && equals(edge, target)) {
           assert(bestOption == null || bestOption.length > newOption.length);

From 06151117ac552828672574b6d967fda942cd7809 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Thu, 7 Jan 2021 17:04:52 +0300
Subject: [PATCH 03/18] null safety

---
 benchmark/shortest_path_benchmark.dart       |  4 +--
 example/crawl_async_example.dart             | 25 +++++++------
 example/example.dart                         |  2 +-
 lib/src/crawl_async.dart                     |  4 +--
 lib/src/shortest_path.dart                   | 28 +++++++--------
 lib/src/strongly_connected_components.dart   | 22 ++++++++----
 pubspec.yaml                                 | 13 ++++---
 test/crawl_async_test.dart                   |  7 ++--
 test/shortest_path_test.dart                 | 37 +++++++-------------
 test/strongly_connected_components_test.dart | 10 +++---
 test/utils/graph.dart                        | 18 +++++-----
 test/utils/utils.dart                        |  4 +--
 12 files changed, 86 insertions(+), 88 deletions(-)

diff --git a/benchmark/shortest_path_benchmark.dart b/benchmark/shortest_path_benchmark.dart
index 813c18b..099468a 100644
--- a/benchmark/shortest_path_benchmark.dart
+++ b/benchmark/shortest_path_benchmark.dart
@@ -21,7 +21,7 @@ void main() {
     }
   }
 
-  int minTicks;
+  int? minTicks;
   var maxIteration = 0;
 
   final testOutput =
@@ -34,7 +34,7 @@ void main() {
     watch
       ..reset()
       ..start();
-    final length = shortestPath(0, size - 1, (e) => graph[e] ?? []).length;
+    final length = shortestPath(0, size - 1, (e) => graph[e] ?? [])?.length;
     watch.stop();
     assert(length == 4, '$length');
 
diff --git a/example/crawl_async_example.dart b/example/crawl_async_example.dart
index ce4c3e3..35a63a7 100644
--- a/example/crawl_async_example.dart
+++ b/example/crawl_async_example.dart
@@ -26,9 +26,9 @@ Future<Null> main() async {
   print(allImports.map((s) => s.uri).toList());
 }
 
-AnalysisContext _analysisContext;
+AnalysisContext? _analysisContext;
 
-Future<AnalysisContext> get analysisContext async {
+Future<AnalysisContext?> get analysisContext async {
   if (_analysisContext == null) {
     var libUri = Uri.parse('package:graphs/');
     var libPath = await pathForUri(libUri);
@@ -39,25 +39,28 @@ Future<AnalysisContext> get analysisContext async {
       throw StateError('Expected to find exactly one context root, got $roots');
     }
 
-    _analysisContext = ContextBuilder().createContext(contextRoot: roots[0]);
+    final analysisContext =
+        ContextBuilder().createContext(contextRoot: roots[0]);
+    _analysisContext = analysisContext;
+    return analysisContext;
   }
 
-  return _analysisContext;
+  return null;
 }
 
-Future<Iterable<Uri>> findImports(Uri from, Source source) async {
-  return source.unit.directives
+Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
+  return source.unit?.directives
       .whereType<UriBasedDirective>()
       .map((d) => d.uri.stringValue)
       .where((uri) => !uri.startsWith('dart:'))
       .map((import) => resolveImport(import, from));
 }
 
-Future<CompilationUnit> parseUri(Uri uri) async {
+Future<CompilationUnit?> parseUri(Uri uri) async {
   var path = await pathForUri(uri);
-  var analysisSession = (await analysisContext).currentSession;
-  var parseResult = analysisSession.getParsedUnit(path);
-  return parseResult.unit;
+  var analysisSession = (await analysisContext)?.currentSession;
+  var parseResult = analysisSession?.getParsedUnit(path);
+  return parseResult?.unit;
 }
 
 Future<String> pathForUri(Uri uri) async {
@@ -81,7 +84,7 @@ Uri resolveImport(String import, Uri from) {
 
 class Source {
   final Uri uri;
-  final CompilationUnit unit;
+  final CompilationUnit? unit;
 
   Source(this.uri, this.unit);
 }
diff --git a/example/example.dart b/example/example.dart
index 47aca61..2fbb8e1 100644
--- a/example/example.dart
+++ b/example/example.dart
@@ -41,7 +41,7 @@ void main() {
   });
 
   var components = stronglyConnectedComponents<Node>(
-      graph.nodes.keys, (node) => graph.nodes[node]);
+      graph.nodes.keys, (node) => graph.nodes[node] ?? []);
 
   print(components);
 }
diff --git a/lib/src/crawl_async.dart b/lib/src/crawl_async.dart
index 2cf0f54..5a74170 100644
--- a/lib/src/crawl_async.dart
+++ b/lib/src/crawl_async.dart
@@ -34,7 +34,7 @@ final _empty = Future<Null>.value(null);
 /// have not completed. If the [edges] callback needs to be limited or throttled
 /// that must be done by wrapping it before calling [crawlAsync].
 Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V> Function(K) readNode,
-    FutureOr<Iterable<K>> Function(K, V) edges) {
+    FutureOr<Iterable<K>?> Function(K, V) edges) {
   final crawl = _CrawlAsync(roots, readNode, edges)..run();
   return crawl.result.stream;
 }
@@ -43,7 +43,7 @@ class _CrawlAsync<K, V> {
   final result = StreamController<V>();
 
   final FutureOr<V> Function(K) readNode;
-  final FutureOr<Iterable<K>> Function(K, V) edges;
+  final FutureOr<Iterable<K>?> Function(K, V) edges;
   final Iterable<K> roots;
 
   final _seen = HashSet<K>();
diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index b58afb5..3905443 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -24,12 +24,12 @@ import 'dart:collection';
 ///
 /// If you supply one of [equals] or [hashCode], you should generally also to
 /// supply the other.
-List<T> shortestPath<T>(
+List<T>? shortestPath<T>(
   T start,
   T target,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(
       start,
@@ -61,8 +61,8 @@ List<T> shortestPath<T>(
 Map<T, List<T>> shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(
       start,
@@ -74,9 +74,9 @@ Map<T, List<T>> shortestPaths<T>(
 Map<T, List<T>> _shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
-  T target,
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  T? target,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) {
   assert(start != null, '`start` cannot be null');
   assert(edges != null, '`edges` cannot be null');
@@ -85,18 +85,18 @@ Map<T, List<T>> _shortestPaths<T>(
   distances[start] = const [];
 
   equals ??= _defaultEquals;
-  if (equals(start, target)) {
+  if (equals.call(start, target)) {
     return distances;
   }
 
   final toVisit = ListQueue<T>()..add(start);
 
-  List<T> bestOption;
+  List<T>? bestOption;
 
   while (toVisit.isNotEmpty) {
     final current = toVisit.removeFirst();
     final currentPath = distances[current];
-    final currentPathLength = currentPath.length;
+    final currentPathLength = currentPath?.length ?? 0;
 
     if (bestOption != null && (currentPathLength + 1) >= bestOption.length) {
       // Skip any existing `toVisit` items that have no chance of being
@@ -111,13 +111,13 @@ Map<T, List<T>> _shortestPaths<T>(
       assert(existingPath == null ||
           existingPath.length <= (currentPathLength + 1));
 
-      if (existingPath == null) {
+      if (existingPath == null && currentPath != null) {
         final newOption = [
           ...currentPath,
           edge,
         ];
 
-        if (equals(edge, target)) {
+        if (target != null && equals(edge, target)) {
           assert(bestOption == null || bestOption.length > newOption.length);
           bestOption = newOption;
         }
@@ -135,4 +135,4 @@ Map<T, List<T>> _shortestPaths<T>(
   return distances;
 }
 
-bool _defaultEquals(Object a, Object b) => a == b;
+bool _defaultEquals<T>(T a, T b) => a == b;
diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index 26018b9..8648957 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -32,8 +32,8 @@ import 'dart:math' show min;
 List<List<T>> stronglyConnectedComponents<T>(
   Iterable<T> nodes,
   Iterable<T> Function(T) edges, {
-  bool Function(T, T) equals,
-  int Function(T) hashCode,
+  bool Function(T?, T?)? equals,
+  int Function(T)? hashCode,
 }) {
   final result = <List<T>>[];
   final lowLinks = HashMap<T, int>(equals: equals, hashCode: hashCode);
@@ -52,12 +52,20 @@ List<List<T>> stronglyConnectedComponents<T>(
     lastVisited.addLast(node);
     onStack.add(node);
     // ignore: omit_local_variable_types
-    for (final T next in edges(node) ?? const []) {
+    for (final T next in edges(node)) {
       if (!indexes.containsKey(next)) {
         strongConnect(next);
-        lowLinks[node] = min(lowLinks[node], lowLinks[next]);
+        final n = lowLinks[node];
+        final x = lowLinks[next];
+        if (n != null && x != null) {
+          lowLinks[node] = min(n, x);
+        }
       } else if (onStack.contains(next)) {
-        lowLinks[node] = min(lowLinks[node], indexes[next]);
+        final n = lowLinks[node];
+        final x = indexes[next];
+        if (n != null && x != null) {
+          lowLinks[node] = min(n, x);
+        }
       }
     }
     if (lowLinks[node] == indexes[node]) {
@@ -67,7 +75,7 @@ List<List<T>> stronglyConnectedComponents<T>(
         next = lastVisited.removeLast();
         onStack.remove(next);
         component.add(next);
-      } while (!equals(next, node));
+      } while (equals?.call(next, node) == false);
       result.add(component);
     }
   }
@@ -78,4 +86,4 @@ List<List<T>> stronglyConnectedComponents<T>(
   return result;
 }
 
-bool _defaultEquals(Object a, Object b) => a == b;
+bool _defaultEquals<T>(T a, T b) => a == b;
diff --git a/pubspec.yaml b/pubspec.yaml
index c27d475..6bc2896 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,16 +1,15 @@
 name: graphs
-version: 0.2.1-dev
+version: 0.3.0-nullsafety.0
 description: Graph algorithms that operate on graphs in any representation
 homepage: https://github.com/dart-lang/graphs
 
 environment:
-  sdk: '>=2.3.0 <3.0.0'
+  sdk: '>=2.12.0-0 <3.0.0'
 
 dev_dependencies:
-  pedantic: ^1.3.0
-  test: ^1.5.1
+  pedantic: ^1.10.0-nullsafety.3
+  test: ^1.16.0-nullsafety.13
 
   # For examples
-  analyzer: '>=0.35.0 <0.42.0'
-  path: ^1.1.0
-  pool: ^1.3.0
+  path: ^1.8.0-nullsafety.3
+  pool: ^1.5.0-nullsafety.3
diff --git a/test/crawl_async_test.dart b/test/crawl_async_test.dart
index 4a0011b..7481264 100644
--- a/test/crawl_async_test.dart
+++ b/test/crawl_async_test.dart
@@ -2,16 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:test/test.dart';
-
 import 'package:graphs/graphs.dart';
+import 'package:test/test.dart';
 
 import 'utils/graph.dart';
 
 void main() {
   group('asyncCrawl', () {
-    Future<List<String>> crawl(
-        Map<String, List<String>> g, Iterable<String> roots) {
+    Future<List<String?>> crawl(
+        Map<String, List<String>?> g, Iterable<String> roots) {
       var graph = AsyncGraph(g);
       return crawlAsync(roots, graph.readNode, graph.edges).toList();
     }
diff --git a/test/shortest_path_test.dart b/test/shortest_path_test.dart
index 3e38067..f787ce3 100644
--- a/test/shortest_path_test.dart
+++ b/test/shortest_path_test.dart
@@ -24,10 +24,10 @@ void main() {
     '6': ['7'],
   };
 
-  List<String> getValues(String key) => graph[key] ?? [];
+  List<String?> getValues(String? key) => graph[key] ?? [];
 
   List<X> getXValues(X key) =>
-      graph[key.value]?.map((v) => X(v))?.toList() ?? [];
+      graph[key.value]?.map((v) => X(v)).toList() ?? [];
 
   test('null `start` throws AssertionError', () {
     expect(() => shortestPath(null, '1', getValues),
@@ -36,30 +36,17 @@ void main() {
         _throwsAssertionError('`start` cannot be null'));
   });
 
-  test('null `edges` throws AssertionError', () {
-    expect(() => shortestPath(1, 1, null),
-        _throwsAssertionError('`edges` cannot be null'));
-    expect(() => shortestPaths(1, null),
-        _throwsAssertionError('`edges` cannot be null'));
-  });
-
   test('null return value from `edges` throws', () {
-    expect(shortestPath(1, 1, (input) => null), <dynamic>[],
-        reason: 'self target short-circuits');
     expect(shortestPath(1, 1, (input) => [null]), <dynamic>[],
         reason: 'self target short-circuits');
 
-    expect(() => shortestPath(1, 2, (input) => null), throwsNoSuchMethodError);
-
-    expect(() => shortestPaths(1, (input) => null), throwsNoSuchMethodError);
-
     expect(() => shortestPath(1, 2, (input) => [null]),
         _throwsAssertionError('`edges` cannot return null values.'));
     expect(() => shortestPaths(1, (input) => [null]),
         _throwsAssertionError('`edges` cannot return null values.'));
   });
 
-  void _singlePathTest(String from, String to, List<String> expected) {
+  void _singlePathTest(String from, String? to, List<String>? expected) {
     test('$from -> $to should be $expected (mapped)', () {
       expect(
           shortestPath<X>(X(from), X(to), getXValues,
@@ -127,7 +114,7 @@ void main() {
     final size = 1000;
     final graph = HashMap<int, List<int>>();
 
-    List<int> resultForGraph() =>
+    List<int>? resultForGraph() =>
         shortestPath<int>(0, size - 1, (e) => graph[e] ?? const []);
 
     void addRandomEdge() {
@@ -139,7 +126,7 @@ void main() {
       }
     }
 
-    List<int> result;
+    List<int>? result;
 
     // Add edges until there is a shortest path between `0` and `size - 1`
     do {
@@ -156,10 +143,10 @@ void main() {
     do {
       expect(++count, lessThan(size * 5), reason: 'This loop should finish.');
       addRandomEdge();
-      final previousResultLength = result.length;
+      final previousResultLength = result?.length;
       result = resultForGraph();
       expect(result, hasLength(lessThanOrEqualTo(previousResultLength)));
-    } while (result.length > 2);
+    } while ((result?.length ?? 0) > 2);
 
     expect(result, [275, 999]);
 
@@ -173,11 +160,13 @@ void main() {
       final randomKey = graph.keys.elementAt(_rnd.nextInt(graph.length));
       final list = graph[randomKey];
       expect(list, isNotEmpty);
-      list.removeAt(_rnd.nextInt(list.length));
-      if (list.isEmpty) {
-        graph.remove(randomKey);
+      if (list != null) {
+        list.removeAt(_rnd.nextInt(list.length));
+        if (list.isEmpty) {
+          graph.remove(randomKey);
+        }
       }
-      final previousResultLength = result.length;
+      final previousResultLength = result?.length;
       result = resultForGraph();
       if (result != null) {
         expect(result, hasLength(greaterThanOrEqualTo(previousResultLength)));
diff --git a/test/strongly_connected_components_test.dart b/test/strongly_connected_components_test.dart
index 6c3968d..11f36d1 100644
--- a/test/strongly_connected_components_test.dart
+++ b/test/strongly_connected_components_test.dart
@@ -12,8 +12,8 @@ void main() {
   group('strongly connected components', () {
     /// Run [stronglyConnectedComponents] on [g].
     List<List<String>> components(
-      Map<String, List<String>> g, {
-      Iterable<String> startNodes,
+      Map<String, List<String>?> g, {
+      Iterable<String>? startNodes,
     }) {
       final graph = Graph(g);
       return stronglyConnectedComponents(
@@ -147,9 +147,9 @@ void main() {
 
   group('custom hashCode and equals', () {
     /// Run [stronglyConnectedComponents] on [g].
-    List<List<String>> components(
-      Map<String, List<String>> g, {
-      Iterable<String> startNodes,
+    List<List<String?>> components(
+      Map<String, List<String>?> g, {
+      Iterable<String?>? startNodes,
     }) {
       final graph = BadGraph(g);
 
diff --git a/test/utils/graph.dart b/test/utils/graph.dart
index f14efe0..96200a2 100644
--- a/test/utils/graph.dart
+++ b/test/utils/graph.dart
@@ -8,11 +8,11 @@ import 'utils.dart';
 
 /// A representation of a Graph since none is specified in `lib/`.
 class Graph {
-  final Map<String, List<String>> _graph;
+  final Map<String, List<String>?> _graph;
 
   Graph(this._graph);
 
-  List<String> edges(String node) => _graph[node];
+  List<String> edges(String node) => _graph[node] ?? [];
 
   Iterable<String> get allNodes => _graph.keys;
 }
@@ -20,12 +20,12 @@ class Graph {
 class BadGraph {
   final Map<X, List<X>> _graph;
 
-  BadGraph(Map<String, List<String>> values)
+  BadGraph(Map<String, List<String>?> values)
       : _graph = LinkedHashMap(equals: xEquals, hashCode: xHashCode)
-          ..addEntries(values.entries.map(
-              (e) => MapEntry(X(e.key), e?.value?.map((v) => X(v))?.toList())));
+          ..addEntries(values.entries.map((e) =>
+              MapEntry(X(e.key), e.value?.map((v) => X(v)).toList() ?? [])));
 
-  List<X> edges(X node) => _graph[node];
+  List<X> edges(X node) => _graph[node] ?? [];
 
   Iterable<X> get allNodes => _graph.keys;
 }
@@ -33,12 +33,12 @@ class BadGraph {
 /// A representation of a Graph where keys can asynchronously be resolved to
 /// real values or to edges.
 class AsyncGraph {
-  final Map<String, List<String>> graph;
+  final Map<String, List<String>?> graph;
 
   AsyncGraph(this.graph);
 
-  Future<String> readNode(String node) async =>
+  Future<String?> readNode(String node) async =>
       graph.containsKey(node) ? node : null;
 
-  Future<Iterable<String>> edges(String key, String node) async => graph[key];
+  Future<Iterable<String>?> edges(String key, String? node) async => graph[key];
 }
diff --git a/test/utils/utils.dart b/test/utils/utils.dart
index f4ed52b..981bad2 100644
--- a/test/utils/utils.dart
+++ b/test/utils/utils.dart
@@ -2,12 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-bool xEquals(X a, X b) => a?.value == b?.value;
+bool xEquals(X? a, X? b) => a?.value == b?.value;
 
 int xHashCode(X a) => a.value.hashCode;
 
 class X {
-  final String value;
+  final String? value;
 
   X(this.value);
 

From 8c08ac45701896bba48fac786bb3c58682a85fc4 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Tue, 9 Feb 2021 21:11:33 +0300
Subject: [PATCH 04/18] dev -> beta

---
 .github/workflows/ci.yml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 687adbd..64e2f8b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,13 +14,13 @@ env:
 
 jobs:
   # Check code formatting and static analysis on a single OS (linux)
-  # against Dart dev.
+  # against Dart beta.
   analyze:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
-        sdk: [dev]
+        sdk: [beta]
     steps:
       - uses: actions/checkout@v2
       - uses: dart-lang/setup-dart@v0.3
@@ -38,7 +38,7 @@ jobs:
 
   # Run tests on a matrix consisting of two dimensions:
   # 1. OS: ubuntu-latest, (macos-latest, windows-latest)
-  # 2. release channel: dev
+  # 2. release channel: beta
   test:
     needs: analyze
     runs-on: ${{ matrix.os }}
@@ -47,7 +47,7 @@ jobs:
       matrix:
         # Add macos-latest and/or windows-latest if relevant for this package.
         os: [ubuntu-latest]
-        sdk: [2.3.0, dev]
+        sdk: [beta]
     steps:
       - uses: actions/checkout@v2
       - uses: dart-lang/setup-dart@v0.3

From a6c49f1a7d9adf08335d5b93cbf7c9780385fa22 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Tue, 9 Feb 2021 21:50:23 +0300
Subject: [PATCH 05/18] analyzer null safety

---
 example/crawl_async_example.dart |  3 ++-
 pubspec.yaml                     | 11 ++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/example/crawl_async_example.dart b/example/crawl_async_example.dart
index 35a63a7..b0d1165 100644
--- a/example/crawl_async_example.dart
+++ b/example/crawl_async_example.dart
@@ -52,7 +52,8 @@ Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
   return source.unit?.directives
       .whereType<UriBasedDirective>()
       .map((d) => d.uri.stringValue)
-      .where((uri) => !uri.startsWith('dart:'))
+      .whereType<String>()
+      .where((uri) => uri.startsWith('dart:') == false)
       .map((import) => resolveImport(import, from));
 }
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 6bc2896..495a532 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,11 +5,12 @@ homepage: https://github.com/dart-lang/graphs
 
 environment:
   sdk: '>=2.12.0-0 <3.0.0'
-
+dependency_overrides:
+  analyzer: ^0.42.0-nullsafety.0
 dev_dependencies:
-  pedantic: ^1.10.0-nullsafety.3
-  test: ^1.16.0-nullsafety.13
+  pedantic: ^1.10.0
+  test: ^1.16.0
 
   # For examples
-  path: ^1.8.0-nullsafety.3
-  pool: ^1.5.0-nullsafety.3
+  path: ^1.8.0
+  pool: ^1.5.0

From b74808c5cc6f071ed8079be0dff348e3a05a91c8 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Tue, 9 Feb 2021 21:51:57 +0300
Subject: [PATCH 06/18] Remove the condition

---
 lib/src/shortest_path.dart | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index 3905443..a41b71d 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -79,7 +79,6 @@ Map<T, List<T>> _shortestPaths<T>(
   int Function(T)? hashCode,
 }) {
   assert(start != null, '`start` cannot be null');
-  assert(edges != null, '`edges` cannot be null');
 
   final distances = HashMap<T, List<T>>(equals: equals, hashCode: hashCode);
   distances[start] = const [];

From 8658a2b42ae1c0734b3e5bf01965c9ae93f06bbd Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 19:39:50 +0300
Subject: [PATCH 07/18] review

---
 lib/src/shortest_path.dart                 | 2 +-
 lib/src/strongly_connected_components.dart | 2 +-
 pubspec.yaml                               | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index a41b71d..847f735 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -84,7 +84,7 @@ Map<T, List<T>> _shortestPaths<T>(
   distances[start] = const [];
 
   equals ??= _defaultEquals;
-  if (equals.call(start, target)) {
+  if (equals(start, target)) {
     return distances;
   }
 
diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index 8648957..1cb5feb 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -75,7 +75,7 @@ List<List<T>> stronglyConnectedComponents<T>(
         next = lastVisited.removeLast();
         onStack.remove(next);
         component.add(next);
-      } while (equals?.call(next, node) == false);
+      } while (!equals!(next, node));
       result.add(component);
     }
   }
diff --git a/pubspec.yaml b/pubspec.yaml
index 495a532..b018919 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,15 +1,15 @@
 name: graphs
-version: 0.3.0-nullsafety.0
+version: 0.3.0
 description: Graph algorithms that operate on graphs in any representation
 homepage: https://github.com/dart-lang/graphs
 
 environment:
   sdk: '>=2.12.0-0 <3.0.0'
-dependency_overrides:
-  analyzer: ^0.42.0-nullsafety.0
+
 dev_dependencies:
   pedantic: ^1.10.0
   test: ^1.16.0
+  analyzer: ^1.0.0
 
   # For examples
   path: ^1.8.0

From 59a09919f038e3b2348316157a81ff7b12aa88e5 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 20:10:26 +0300
Subject: [PATCH 08/18] fix

---
 pubspec.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pubspec.yaml b/pubspec.yaml
index b018919..ce28a46 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -9,8 +9,8 @@ environment:
 dev_dependencies:
   pedantic: ^1.10.0
   test: ^1.16.0
-  analyzer: ^1.0.0
 
   # For examples
   path: ^1.8.0
   pool: ^1.5.0
+  analyzer: ^1.0.0

From df84a7b9455223ee8b6eabb194fcb3bf3234e32a Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 20:52:22 +0300
Subject: [PATCH 09/18] review

---
 example/crawl_async_example.dart | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/example/crawl_async_example.dart b/example/crawl_async_example.dart
index b0d1165..c4e6dbb 100644
--- a/example/crawl_async_example.dart
+++ b/example/crawl_async_example.dart
@@ -28,7 +28,7 @@ Future<Null> main() async {
 
 AnalysisContext? _analysisContext;
 
-Future<AnalysisContext?> get analysisContext async {
+Future<AnalysisContext> get analysisContext async {
   if (_analysisContext == null) {
     var libUri = Uri.parse('package:graphs/');
     var libPath = await pathForUri(libUri);
@@ -45,7 +45,7 @@ Future<AnalysisContext?> get analysisContext async {
     return analysisContext;
   }
 
-  return null;
+  return _analysisContext!;
 }
 
 Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
@@ -57,11 +57,11 @@ Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
       .map((import) => resolveImport(import, from));
 }
 
-Future<CompilationUnit?> parseUri(Uri uri) async {
+Future<CompilationUnit> parseUri(Uri uri) async {
   var path = await pathForUri(uri);
-  var analysisSession = (await analysisContext)?.currentSession;
-  var parseResult = analysisSession?.getParsedUnit(path);
-  return parseResult?.unit;
+  var analysisSession = (await analysisContext).currentSession;
+  var parseResult = analysisSession.getParsedUnit(path);
+  return parseResult.unit;
 }
 
 Future<String> pathForUri(Uri uri) async {

From f354b05f00d987d8443ef0cf38539ae3460992a6 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:24:32 +0300
Subject: [PATCH 10/18] just T

---
 example/crawl_async_example.dart | 6 +++---
 lib/src/shortest_path.dart       | 4 ++--
 test/utils/graph.dart            | 3 ++-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/example/crawl_async_example.dart b/example/crawl_async_example.dart
index c4e6dbb..b9a8d23 100644
--- a/example/crawl_async_example.dart
+++ b/example/crawl_async_example.dart
@@ -48,8 +48,8 @@ Future<AnalysisContext> get analysisContext async {
   return _analysisContext!;
 }
 
-Future<Iterable<Uri>?> findImports(Uri from, Source source) async {
-  return source.unit?.directives
+Future<Iterable<Uri>> findImports(Uri from, Source source) async {
+  return source.unit.directives
       .whereType<UriBasedDirective>()
       .map((d) => d.uri.stringValue)
       .whereType<String>()
@@ -85,7 +85,7 @@ Uri resolveImport(String import, Uri from) {
 
 class Source {
   final Uri uri;
-  final CompilationUnit? unit;
+  final CompilationUnit unit;
 
   Source(this.uri, this.unit);
 }
diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index 847f735..97c9d23 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -75,7 +75,7 @@ Map<T, List<T>> _shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
   T? target,
-  bool Function(T?, T?)? equals,
+  bool Function(T, T)? equals,
   int Function(T)? hashCode,
 }) {
   assert(start != null, '`start` cannot be null');
@@ -84,7 +84,7 @@ Map<T, List<T>> _shortestPaths<T>(
   distances[start] = const [];
 
   equals ??= _defaultEquals;
-  if (equals(start, target)) {
+  if (target != null && equals(start, target)) {
     return distances;
   }
 
diff --git a/test/utils/graph.dart b/test/utils/graph.dart
index 96200a2..3bb1c06 100644
--- a/test/utils/graph.dart
+++ b/test/utils/graph.dart
@@ -40,5 +40,6 @@ class AsyncGraph {
   Future<String?> readNode(String node) async =>
       graph.containsKey(node) ? node : null;
 
-  Future<Iterable<String>?> edges(String key, String? node) async => graph[key];
+  Future<Iterable<String>> edges(String key, String? node) async =>
+      graph[key] ?? [];
 }

From 741d6d08184cd3b6192b3e5381caf3d6a6f7526a Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:27:18 +0300
Subject: [PATCH 11/18] ?currentPath

---
 lib/src/shortest_path.dart | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index 97c9d23..d2c1a8c 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -110,9 +110,9 @@ Map<T, List<T>> _shortestPaths<T>(
       assert(existingPath == null ||
           existingPath.length <= (currentPathLength + 1));
 
-      if (existingPath == null && currentPath != null) {
+      if (existingPath == null) {
         final newOption = [
-          ...currentPath,
+          ...?currentPath,
           edge,
         ];
 

From c02f50b380ea9ce92bcccceef86c628dc30f6753 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:30:05 +0300
Subject: [PATCH 12/18] fix

---
 lib/src/shortest_path.dart | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index d2c1a8c..85d64ac 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -28,7 +28,7 @@ List<T>? shortestPath<T>(
   T start,
   T target,
   Iterable<T> Function(T) edges, {
-  bool Function(T?, T?)? equals,
+  bool Function(T, T)? equals,
   int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(
@@ -61,7 +61,7 @@ List<T>? shortestPath<T>(
 Map<T, List<T>> shortestPaths<T>(
   T start,
   Iterable<T> Function(T) edges, {
-  bool Function(T?, T?)? equals,
+  bool Function(T, T)? equals,
   int Function(T)? hashCode,
 }) =>
     _shortestPaths<T>(

From 339abbb37f0e14450544b64cf52290b58cf3d795 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:32:02 +0300
Subject: [PATCH 13/18] fix

---
 lib/src/strongly_connected_components.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index 1cb5feb..3faad03 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -32,7 +32,7 @@ import 'dart:math' show min;
 List<List<T>> stronglyConnectedComponents<T>(
   Iterable<T> nodes,
   Iterable<T> Function(T) edges, {
-  bool Function(T?, T?)? equals,
+  bool Function(T, T)? equals,
   int Function(T)? hashCode,
 }) {
   final result = <List<T>>[];

From 2c454ea782f905d4e649a5242ae5bccc21b1f05f Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:36:24 +0300
Subject: [PATCH 14/18] fix _defaultEquals

Co-authored-by: Jacob MacDonald <jakemac@google.com>
---
 lib/src/shortest_path.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/src/shortest_path.dart b/lib/src/shortest_path.dart
index 85d64ac..3711960 100644
--- a/lib/src/shortest_path.dart
+++ b/lib/src/shortest_path.dart
@@ -134,4 +134,4 @@ Map<T, List<T>> _shortestPaths<T>(
   return distances;
 }
 
-bool _defaultEquals<T>(T a, T b) => a == b;
+bool _defaultEquals(Object? a, Object? b) => a == b;

From d78bd8045dff5c6197d00c55f43bafb7e0e72f8a Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 21:45:28 +0300
Subject: [PATCH 15/18] added some !

---
 lib/src/strongly_connected_components.dart | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index 3faad03..abdd7bf 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -55,17 +55,9 @@ List<List<T>> stronglyConnectedComponents<T>(
     for (final T next in edges(node)) {
       if (!indexes.containsKey(next)) {
         strongConnect(next);
-        final n = lowLinks[node];
-        final x = lowLinks[next];
-        if (n != null && x != null) {
-          lowLinks[node] = min(n, x);
-        }
+        lowLinks[node] = min(lowLinks[node]!, lowLinks[next]!);
       } else if (onStack.contains(next)) {
-        final n = lowLinks[node];
-        final x = indexes[next];
-        if (n != null && x != null) {
-          lowLinks[node] = min(n, x);
-        }
+        lowLinks[node] = min(lowLinks[node]!, indexes[next]!);
       }
     }
     if (lowLinks[node] == indexes[node]) {

From b13c4ebee5d142fbc7ac0302bf1937eb4f7be135 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 22:05:22 +0300
Subject: [PATCH 16/18] Object?

---
 lib/src/strongly_connected_components.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/src/strongly_connected_components.dart b/lib/src/strongly_connected_components.dart
index abdd7bf..e4ce1f2 100644
--- a/lib/src/strongly_connected_components.dart
+++ b/lib/src/strongly_connected_components.dart
@@ -78,4 +78,4 @@ List<List<T>> stronglyConnectedComponents<T>(
   return result;
 }
 
-bool _defaultEquals<T>(T a, T b) => a == b;
+bool _defaultEquals(Object? a, Object? b) => a == b;

From a19da5b30388752a62d0eb96d38f371311c0cebf Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 23:23:27 +0300
Subject: [PATCH 17/18] The documentation says that readNode is allowed to
 return null

---
 lib/src/crawl_async.dart | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/src/crawl_async.dart b/lib/src/crawl_async.dart
index 5a74170..9979d5f 100644
--- a/lib/src/crawl_async.dart
+++ b/lib/src/crawl_async.dart
@@ -33,7 +33,7 @@ final _empty = Future<Null>.value(null);
 /// Crawling is eager, so calls to [edges] may overlap with other calls that
 /// have not completed. If the [edges] callback needs to be limited or throttled
 /// that must be done by wrapping it before calling [crawlAsync].
-Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V> Function(K) readNode,
+Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V?> Function(K) readNode,
     FutureOr<Iterable<K>?> Function(K, V) edges) {
   final crawl = _CrawlAsync(roots, readNode, edges)..run();
   return crawl.result.stream;
@@ -42,7 +42,7 @@ Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V> Function(K) readNode,
 class _CrawlAsync<K, V> {
   final result = StreamController<V>();
 
-  final FutureOr<V> Function(K) readNode;
+  final FutureOr<V?> Function(K) readNode;
   final FutureOr<Iterable<K>?> Function(K, V) edges;
   final Iterable<K> roots;
 

From 291cf401dfddeb0345b1b4c822a46240831415c6 Mon Sep 17 00:00:00 2001
From: hovadur <hovadur@gmail.com>
Date: Fri, 19 Feb 2021 23:46:52 +0300
Subject: [PATCH 18/18] removed the trick like ?? const <Never>[]

---
 lib/src/crawl_async.dart   | 6 +++---
 test/crawl_async_test.dart | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/src/crawl_async.dart b/lib/src/crawl_async.dart
index 9979d5f..821e296 100644
--- a/lib/src/crawl_async.dart
+++ b/lib/src/crawl_async.dart
@@ -34,7 +34,7 @@ final _empty = Future<Null>.value(null);
 /// have not completed. If the [edges] callback needs to be limited or throttled
 /// that must be done by wrapping it before calling [crawlAsync].
 Stream<V> crawlAsync<K, V>(Iterable<K> roots, FutureOr<V?> Function(K) readNode,
-    FutureOr<Iterable<K>?> Function(K, V) edges) {
+    FutureOr<Iterable<K>> Function(K, V) edges) {
   final crawl = _CrawlAsync(roots, readNode, edges)..run();
   return crawl.result.stream;
 }
@@ -43,7 +43,7 @@ class _CrawlAsync<K, V> {
   final result = StreamController<V>();
 
   final FutureOr<V?> Function(K) readNode;
-  final FutureOr<Iterable<K>?> Function(K, V) edges;
+  final FutureOr<Iterable<K>> Function(K, V) edges;
   final Iterable<K> roots;
 
   final _seen = HashSet<K>();
@@ -69,7 +69,7 @@ class _CrawlAsync<K, V> {
     if (value == null) return;
     if (result.isClosed) return;
     result.add(value);
-    var next = await edges(key, value) ?? const [];
+    var next = await edges(key, value);
     await Future.wait(next.map(_visit), eagerError: true);
   }
 
diff --git a/test/crawl_async_test.dart b/test/crawl_async_test.dart
index 7481264..4884c85 100644
--- a/test/crawl_async_test.dart
+++ b/test/crawl_async_test.dart
@@ -87,7 +87,7 @@ void main() {
         'a': ['b'],
       };
       var nodes = crawlAsync(['a'], (n) => n,
-          (k, n) => k == 'b' ? throw ArgumentError() : graph[k]);
+          (k, n) => k == 'b' ? throw ArgumentError() : graph[k]!);
       expect(nodes, emitsThrough(emitsError(isArgumentError)));
     });
 
@@ -96,7 +96,7 @@ void main() {
         'a': ['b'],
       };
       var nodes = crawlAsync(['a'], (n) => n == 'b' ? throw ArgumentError() : n,
-          (k, n) => graph[k]);
+          (k, n) => graph[k]!);
       expect(nodes, emitsThrough(emitsError(isArgumentError)));
     });
   });