[hooks_runner] Optimize the no hooks path (#2302)

Bug: #2236

Optimize the code paths for when there are no hooks (speeds up standalone Dart).

* Return early in various places, and check if there are hooks at all as first thing.
* Write JSON encoding instead of YAML encoding. 17 ms -> 1 ms on a small JSON object. (And JSON is valid YAML.)

After this the longest running part in `dartdev` is loading the `package_config.json`: 10 ms. We can't really avoid this because we need that info to check whether we have any hooks that need running. And the `package_config.json` isn't already loaded by dartdev (in contrast to `flutter_tools` where we have a `PackageConfig` object available). dartdev delegates compilation to `package:pub`(!) via `getExecutableForCommand` and that API uses the package config file path. dart-lang/pub#4067

Author: dcharkes

pkgs/hooks_runner/lib/src/build_runner/build_planner.dart

@@ -116,6 +116,10 @@ class NativeAssetsBuildPlanner {
   Future<Result<BuildPlan, HooksRunnerFailure>> makeBuildHookPlan() async {
     if (_buildHookPlan != null) return Success(_buildHookPlan!);
     final packagesWithNativeAssets = await packagesWithHook(Hook.build);
+    if (packagesWithNativeAssets.isEmpty) {
+      // Avoid calculating the package graph if there are no hooks.
+      return const Success([]);
+    }
     final packageMap = {
       for (final package in packagesWithNativeAssets) package.name: package,
     };

pkgs/hooks_runner/lib/src/build_runner/build_runner.dart

@@ -113,19 +113,23 @@ class NativeAssetsBuildRunner {
     required List<ProtocolExtension> extensions,
     required bool linkingEnabled,
   }) async {
+    final planResult = await _makePlan(hook: Hook.build, buildResult: null);
+    if (planResult.isFailure) {
+      return planResult.asFailure;
+    }
+    final (buildPlan, packageGraph) = planResult.success;
+    if (buildPlan.isEmpty) {
+      // Return eagerly if there are no build hooks at all.
+      return Success(HookResult());
+    }
+
     final loadedUserDefines = await _loadedUserDefines;
     final hookResultUserDefines = await _checkUserDefines(loadedUserDefines);
     if (hookResultUserDefines.isFailure) {
       return hookResultUserDefines;
     }
     var hookResult = hookResultUserDefines.success;
 
-    final planResult = await _makePlan(hook: Hook.build, buildResult: null);
-    if (planResult.isFailure) {
-      return planResult.asFailure;
-    }
-    final (buildPlan, packageGraph) = planResult.success;
-
     /// Key is packageName.
     final globalAssetsForBuild = <String, List<EncodedAsset>>{};
     for (final package in buildPlan) {

pkgs/hooks_runner/lib/src/model/kernel_assets.dart

@@ -14,7 +14,8 @@
 /// Dart SDK.
 library;
 
-import '../utils/yaml.dart';
+import 'dart:convert';
+
 import 'target.dart';
 
 class KernelAssets {
@@ -30,7 +31,7 @@ class KernelAssets {
       assetsPerTarget[asset.target] = assets;
     }
 
-    final yamlContents = {
+    final jsonContents = {
       'format-version': [1, 0, 0],
       'native-assets': {
         for (final entry in assetsPerTarget.entries)
@@ -40,7 +41,7 @@ class KernelAssets {
       },
     };
 
-    return yamlEncode(yamlContents);
+    return const JsonEncoder.withIndent('  ').convert(jsonContents);
   }
 }
 

pkgs/hooks_runner/lib/src/utils/yaml.dart

@@ -23,7 +23,6 @@ dependencies:
   package_config: ^2.1.0
   pub_semver: ^2.2.0
   yaml: ^3.1.3
-  yaml_edit: ^2.2.2
 
 dev_dependencies:
   custom_lint: ^0.7.5

pkgs/hooks_runner/pubspec.yaml

@@ -52,37 +52,54 @@ void main() {
     ),
   ]);
 
-  final assetsDartEncoding = '''format-version:
-  - 1
-  - 0
-  - 0
-native-assets:
-  android_x64:
-    foo:
-      - absolute
-      - ${fooUri.toFilePath()}
-    foo2:
-      - relative
-      - ${foo2Uri.toFilePath()}
-    foo3:
-      - system
-      - ${foo3Uri.toFilePath()}
-    foo4:
-      - executable
-    foo5:
-      - process
-  linux_arm64:
-    bar:
-      - absolute
-      - ${barUri.toFilePath()}
-  windows_x64:
-    bla:
-      - absolute
-      - ${blaUri.toFilePath()}''';
+  final assetsDartEncoding = '''{
+  "format-version": [
+    1,
+    0,
+    0
+  ],
+  "native-assets": {
+    "android_x64": {
+      "foo": [
+        "absolute",
+        "${fooUri.toFilePath()}"
+      ],
+      "foo2": [
+        "relative",
+        "${foo2Uri.toFilePath()}"
+      ],
+      "foo3": [
+        "system",
+        "${foo3Uri.toFilePath()}"
+      ],
+      "foo4": [
+        "executable"
+      ],
+      "foo5": [
+        "process"
+      ]
+    },
+    "linux_arm64": {
+      "bar": [
+        "absolute",
+        "${barUri.toFilePath()}"
+      ]
+    },
+    "windows_x64": {
+      "bla": [
+        "absolute",
+        "${blaUri.toFilePath()}"
+      ]
+    }
+  }
+}''';
 
   test('asset yaml', () async {
     final fileContents = assets.toNativeAssetsFile();
-    expect(fileContents, assetsDartEncoding);
+    expect(
+      fileContents.replaceAll(r'\ ', ' ').replaceAll(r'\\', r'\'),
+      assetsDartEncoding,
+    );
   });
 
   test('path equality', () {