Merge pull request #2528 from alhaad/depsfile_hook

Add `flutter_tools build` hooks to also generate depfile.

packages/flutter_tools/lib/src/commands/build.dart

@@ -23,6 +23,7 @@ class BuildCommand extends FlutterCommand {
     argParser.addOption('private-key', defaultsTo: defaultPrivateKeyPath);
     argParser.addOption('output-file', abbr: 'o', defaultsTo: defaultFlxOutputPath);
     argParser.addOption('snapshot', defaultsTo: defaultSnapshotPath);
+    argParser.addOption('depfile', defaultsTo: defaultDepfilePath);
     addTargetOption();
   }
 
@@ -42,6 +43,7 @@ class BuildCommand extends FlutterCommand {
       manifestPath: argResults['manifest'],
       outputPath: outputPath,
       snapshotPath: argResults['snapshot'],
+      depfilePath: argResults['depfile'],
       privateKeyPath: argResults['private-key'],
       precompiledSnapshot: argResults['precompiled']
     ).then((int result) {

packages/flutter_tools/lib/src/flx.dart

@@ -22,6 +22,7 @@ const String defaultAssetBasePath = '.';
 const String defaultManifestPath = 'flutter.yaml';
 const String defaultFlxOutputPath = 'build/app.flx';
 const String defaultSnapshotPath = 'build/snapshot_blob.bin';
+const String defaultDepfilePath = 'build/snapshot_blob.bin.d';
 const String defaultPrivateKeyPath = 'privatekey.der';
 
 const String _kSnapshotKey = 'snapshot_blob.bin';
@@ -160,6 +161,7 @@ Future<int> build(
   String manifestPath: defaultManifestPath,
   String outputPath: defaultFlxOutputPath,
   String snapshotPath: defaultSnapshotPath,
+  String depfilePath: defaultDepfilePath,
   String privateKeyPath: defaultPrivateKeyPath,
   bool precompiledSnapshot: false
 }) async {
@@ -173,7 +175,7 @@ Future<int> build(
 
     // In a precompiled snapshot, the instruction buffer contains script
     // content equivalents
-    int result = await toolchain.compiler.compile(mainPath: mainPath, snapshotPath: snapshotPath);
+    int result = await toolchain.compiler.compile(mainPath: mainPath, snapshotPath: snapshotPath, depfilePath: depfilePath, buildOutputPath: outputPath);
     if (result != 0) {
       printError('Failed to run the Flutter compiler. Exit code: $result');
       return result;

packages/flutter_tools/lib/src/toolchain.dart

@@ -18,14 +18,23 @@ class Compiler {
 
   Future<int> compile({
     String mainPath,
-    String snapshotPath
+    String snapshotPath,
+    String depfilePath,
+    String buildOutputPath
   }) {
-    return runCommandAndStreamOutput([
+    final List<String> args = [
       _path,
       mainPath,
       '--package-root=${ArtifactStore.packageRoot}',
       '--snapshot=$snapshotPath'
-    ]);
+    ];
+    if (depfilePath != null) {
+      args.add('--depfile=$depfilePath');
+    }
+    if (buildOutputPath != null) {
+      args.add('--build-output=$buildOutputPath');
+    }
+    return runCommandAndStreamOutput(args);
   }
 }