[gn] Change sdk_rewriter() template to use depfiles (#51314)

Part of flutter/flutter#144430

From `gn help inputs`: "It may be tempting to write a script that enumerates all files in a directory
as inputs. Don't do this!"

Author: zanderso

web_sdk/BUILD.gn

@@ -41,7 +41,7 @@ sdk_rewriter("web_ui_library_sources") {
   output_dir = "$root_out_dir/flutter_web_sdk/lib/ui/"
 
   # exclude everything in the engine directory, it will be a separate internal library
-  exclude_patterns = [ rebase_path("//flutter/lib/web_ui/lib/src/*") ]
+  exclude_pattern = rebase_path("//flutter/lib/web_ui/lib/src")
 }
 
 web_ui_ui_web_with_output("web_ui_ui_web") {
@@ -55,8 +55,7 @@ sdk_rewriter("web_engine_library") {
   output_dir = "$root_out_dir/flutter_web_sdk/lib/_engine/"
 
   # exclude skwasm, it will be a separate internal library
-  exclude_patterns =
-      [ rebase_path("//flutter/lib/web_ui/lib/src/engine/skwasm/*") ]
+  exclude_pattern = rebase_path("//flutter/lib/web_ui/lib/src/engine/skwasm")
 }
 
 sdk_rewriter("skwasm_stub_library") {

web_sdk/sdk_rewriter.dart

@@ -15,7 +15,10 @@ final ArgParser argParser = ArgParser()
   ..addOption('library-name')
   ..addOption('api-file')
   ..addMultiOption('source-file')
-  ..addOption('stamp');
+  ..addOption('stamp')
+  ..addOption('depfile')
+  ..addOption('exclude-pattern')
+  ..addOption('build-dir');
 
 final List<Replacer> uiPatterns = <Replacer>[
   AllReplacer(RegExp(r'library\s+ui;'), 'library dart.ui;'),
@@ -113,6 +116,10 @@ void main(List<String> arguments) {
   final ArgResults results = argParser.parse(arguments);
   final Directory directory = Directory(results['output-dir'] as String);
   final String inputDirectoryPath = results['input-dir'] as String;
+  final String? excludePattern = results['exclude-pattern'] as String?;
+  final String stampfilePath = results['stamp'] as String;
+  final String depfilePath = results['depfile'] as String;
+  final String buildDirPath = results['build-dir'] as String;
 
   String Function(String source)? preprocessor;
   List<Replacer> replacementPatterns;
@@ -130,13 +137,25 @@ void main(List<String> arguments) {
     preprocessor = (String source) => preprocessPartFile(source, libraryName!);
     replacementPatterns = generatePartsPatterns(libraryName, isPublic);
   }
-  for (final String inputFilePath in results['source-file'] as Iterable<String>) {
-    String pathSuffix = inputFilePath.substring(inputDirectoryPath.length);
+
+  final List<String> inputFiles = <String>[];
+  final List<FileSystemEntity> entries = Directory(inputDirectoryPath).listSync(
+    recursive: true, followLinks: false,
+  );
+  for (final File inputFile in entries.whereType<File>()) {
+    if (excludePattern != null && inputFile.path.startsWith(excludePattern)) {
+      continue;
+    }
+    if (!inputFile.path.endsWith('.dart') || inputFile.path.endsWith('_test.dart')) {
+      continue;
+    }
+    inputFiles.add(path.relative(inputFile.path, from: buildDirPath));
+    String pathSuffix = inputFile.path.substring(inputDirectoryPath.length);
     if (libraryName != null) {
       pathSuffix = path.join(libraryName, pathSuffix);
     }
     final String outputFilePath = path.join(directory.path, pathSuffix);
-    processFile(inputFilePath, outputFilePath, preprocessor, replacementPatterns);
+    processFile(inputFile.path, outputFilePath, preprocessor, replacementPatterns);
   }
 
   if (results['api-file'] != null) {
@@ -159,10 +178,15 @@ void main(List<String> arguments) {
     );
   }
 
+  File(stampfilePath).writeAsStringSync('stamp');
+  writeDepfile(depfilePath, stampfilePath, inputFiles);
+}
 
-  if (results['stamp'] != null) {
-    File(results['stamp'] as String).writeAsStringSync('stamp');
-  }
+void writeDepfile(String depfilePath, String stampfilePath, List<String> inputFiles) {
+  final StringBuffer outBuf = StringBuffer();
+  outBuf.write('$stampfilePath: ');
+  outBuf.write(inputFiles.join(' '));
+  File(depfilePath).writeAsStringSync(outBuf.toString());
 }
 
 List<String> getExtraImportsForLibrary(String libraryName) {

web_sdk/web_sdk.gni

@@ -18,42 +18,41 @@ template("sdk_rewriter") {
   assert(defined(invoker.input_dir), "Must pass 'input_dir'")
   assert(defined(invoker.output_dir), "Must pass 'output_dir'")
 
-  source_dart_files = exec_script("$dart_src/tools/list_dart_files.py",
-                                  [
-                                    "absolute",
-                                    rebase_path(invoker.input_dir),
-                                  ],
-                                  "list lines")
-
-  if (defined(invoker.exclude_patterns)) {
-    filtered_files = filter_exclude(source_dart_files, invoker.exclude_patterns)
-    source_dart_files = []
-    source_dart_files = filtered_files
-  }
-
   prebuilt_dart_action(target_name) {
     packages = dart_sdk_package_config
     pool = "//flutter/build/dart:dart_pool"
 
     script = "//flutter/web_sdk/sdk_rewriter.dart"
-    inputs = source_dart_files + [ script ]
+
+    depfile = "$target_gen_dir/$target_name.d"
 
     stamp_location = "$target_gen_dir/$target_name.stamp"
     outputs = [
       stamp_location,
       invoker.output_dir,
     ]
 
+    build_dir = rebase_path(root_out_dir)
     input_dir = rebase_path(invoker.input_dir)
     output_dir = rebase_path(invoker.output_dir)
 
     args = [
+      "--build-dir=$build_dir",
       "--output-dir=$output_dir",
       "--input-dir=$input_dir",
+      "--depfile",
+      rebase_path(depfile),
       "--stamp",
       rebase_path(stamp_location, root_build_dir),
     ]
 
+    if (defined(invoker.exclude_pattern)) {
+      args += [
+        "--exclude-pattern",
+        invoker.exclude_pattern,
+      ]
+    }
+
     if (defined(invoker.is_public) && invoker.is_public) {
       args += [ "--public" ]
     }
@@ -68,11 +67,6 @@ template("sdk_rewriter") {
         "--api-file=$api_file",
       ]
     }
-
-    foreach(source_file, source_dart_files) {
-      path = rebase_path(source_file)
-      args += [ "--source-file=$path" ]
-    }
   }
 }