Add the ability to inject a bootstrap script (#66897)

.gitignore

@@ -24,6 +24,8 @@
 
 # Flutter repo-specific
 /bin/cache/
+/bin/internal/bootstrap.bat
+/bin/internal/bootstrap.sh
 /bin/mingit/
 /dev/benchmarks/mega_gallery/
 /dev/bots/.recipe_deps

bin/internal/shared.bat

@@ -61,6 +61,12 @@ IF NOT EXIST "%cache_dir%" (
 GOTO :after_subroutine
 
 :subroutine
+  REM If present, run the bootstrap script first
+  SET bootstrap_path=%FLUTTER_ROOT%\bin\internal\bootstrap.bat
+  IF EXIST "%bootstrap_path%" (
+    CALL "%bootstrap_path%"
+  )
+
   PUSHD "%flutter_root%"
   FOR /f %%r IN ('git rev-parse HEAD') DO SET revision=%%r
   POPD

bin/internal/shared.sh

@@ -166,6 +166,12 @@ function upgrade_flutter () (
 function shared::execute() {
   export FLUTTER_ROOT="$(cd "${BIN_DIR}/.." ; pwd -P)"
 
+  # If present, run the bootstrap script first
+  BOOTSTRAP_PATH="$FLUTTER_ROOT/bin/internal/bootstrap.sh"
+  if [ -f "$BOOTSTRAP_PATH" ]; then
+    source "$BOOTSTRAP_PATH"
+  fi
+
   FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
   SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
   STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"

packages/flutter_tools/test/integration.shard/command_output_test.dart

@@ -170,4 +170,28 @@ void main() {
     expect(result.exitCode, 1);
     expect(result.stderr, contains('Invalid `--debug-uri`: http://127.0.0.1:3333*/'));
   });
+
+  testWithoutContext('will load bootstrap script before starting', () async {
+    final String flutterBin =
+        fileSystem.path.join(getFlutterRoot(), 'bin', 'flutter');
+
+    final File bootstrap = fileSystem.file(fileSystem.path.join(
+        getFlutterRoot(),
+        'bin',
+        'internal',
+        platform.isWindows ? 'bootstrap.bat' : 'bootstrap.sh'));
+
+    try {
+      bootstrap.writeAsStringSync('echo TESTING 1 2 3');
+
+      final ProcessResult result = await processManager.run(<String>[
+        flutterBin,
+        ...getLocalEngineArguments(),
+      ]);
+
+      expect(result.stdout, contains('TESTING 1 2 3'));
+    } finally {
+      bootstrap.deleteSync();
+    }
+  });
 }