CPLAT-5152: Optimize builder's use of asset reads to avoid unnecessary rebuilds

build.yaml

@@ -23,6 +23,7 @@ targets:
           exclude:
             # This tests un-built behavior, and therefore should not be built
             - "test/over_react/component_declaration/builder_helpers_test.dart"
+
       over_react|overReactBuilder:
         enabled: false
 
@@ -37,13 +38,9 @@ targets:
             - "web/**"
           exclude:
             - "lib/src/builder/**"
+
       build_web_compilers|entrypoint:
         generate_for:
-          include:
-            - "example/**"
-            - "lib/*.dart"
-            - "test/*.dart"
-            - "web/*.dart"
-          exclude:
-            - "lib/src/builder/**"
-
+          - "example/**.dart"
+          - "test/*.browser_test.dart"
+          - "web/*.dart"

lib/src/builder/builder.dart

@@ -1,8 +1,142 @@
+import 'dart:async';
+
+import 'package:analyzer/analyzer.dart';
 import 'package:build/build.dart';
-import 'package:source_gen/source_gen.dart';
+import 'package:dart_style/dart_style.dart';
+import 'package:over_react/src/builder/generation/declaration_parsing.dart';
+import 'package:over_react/src/builder/generation/impl_generation.dart';
+import 'package:path/path.dart' as p;
+import 'package:source_span/source_span.dart';
 
 import './util.dart';
-import './generator.dart';
 
-Builder overReactBuilder(BuilderOptions options) =>
-    new PartBuilder([new OverReactGenerator()], outputExtension);
+Builder overReactBuilder(BuilderOptions options) => new OverReactBuilder();
+
+class OverReactBuilder extends Builder {
+  @override
+  Map<String, List<String>> get buildExtensions => {
+    '.dart': [outputExtension],
+  };
+
+  @override
+  FutureOr<void> build(BuildStep buildStep) async {
+    final source = await buildStep.readAsString(buildStep.inputId);
+    final libraryUnit = _tryParseCompilationUnit(source, buildStep.inputId);
+    if (libraryUnit == null) {
+      return;
+    }
+    if (isPart(libraryUnit)) {
+      return;
+    }
+
+    final outputs = <String>[];
+    void generateForFile(String source, AssetId id, CompilationUnit unit) {
+      if (!ParsedDeclarations.mightContainDeclarations(source)) {
+        return;
+      }
+      final sourceFile = new SourceFile.fromString(
+        source, url: idToPackageUri(id));
+      final declarations = new ParsedDeclarations(unit, sourceFile, log);
+      if (declarations.hasErrors) {
+        log.severe('There was an error parsing the file declarations for file: $id');
+        return;
+      }
+      final generator = new ImplGenerator(log, sourceFile)
+        ..generate(declarations);
+      final generatedOutput = generator.outputContentsBuffer.toString().trim();
+      if (generatedOutput.isNotEmpty) {
+        outputs.add(generatedOutput);
+      }
+    }
+
+    // Collect all of the part files for this library.
+    final parts = libraryUnit.directives
+      .whereType<PartDirective>()
+      // Ignore all generated `.g.dart` parts.
+      .where((part) => !part.uri.stringValue.endsWith('.g.dart'));
+
+    // Generate over_react code for the input library.
+    generateForFile(source, buildStep.inputId, libraryUnit);
+
+    // Generate over_react code for each part file of the input library.
+    for (final part in parts) {
+      final partId = new AssetId.resolve(
+        part.uri.stringValue,
+        from: buildStep.inputId);
+      if (!await buildStep.canRead(partId)) {
+        continue;
+      }
+      final partSource = await buildStep.readAsString(partId);
+      final partUnit = _tryParseCompilationUnit(partSource, partId);
+      if (partUnit == null) {
+        continue;
+      }
+      generateForFile(partSource, partId, partUnit);
+    }
+
+    if (outputs.isNotEmpty) {
+      final outputId = buildStep.inputId.changeExtension(outputExtension);
+
+      // Verify that the library file has an `.over_react.g.dart` part.
+      final expectedPart = p.basename(outputId.path);
+      final partUris = libraryUnit.directives
+        .whereType<PartDirective>()
+        .map((p) => p.uri.stringValue);
+      if (!partUris.contains(expectedPart)) {
+        log.warning('Missing "part \'$expectedPart\';".');
+      }
+
+      await _writePart(buildStep, outputId, outputs);
+    }
+  }
+
+  static final _headerLine = '// '.padRight(77, '*');
+
+  static final _formatter = new DartFormatter();
+
+  static final RegExp _overReactPartDirective = new RegExp(
+    r'''['"].*\.over_react\.g\.dart['"]''',
+  );
+
+  static bool _mightContainDeclarations(String source) {
+    return ParsedDeclarations.mightContainDeclarations(source) ||
+      _overReactPartDirective.hasMatch(source);
+  }
+
+  static CompilationUnit _tryParseCompilationUnit(String source, AssetId id) {
+    try {
+      return parseCompilationUnit(
+        source,
+        name: id.path,
+        suppressErrors: false,
+        parseFunctionBodies: true);
+    } catch (error, stackTrace) {
+      log.severe('There was an error parsing the compilation unit for file: $id');
+      log.fine(error);
+      log.fine(stackTrace);
+      return null;
+    }
+  }
+
+  static FutureOr<void> _writePart(BuildStep buildStep, AssetId outputId, Iterable<String> outputs) async {
+    final partOf = "'${p.basename(buildStep.inputId.uri.toString())}'";
+
+    final buffer = new StringBuffer()
+      ..writeln('// GENERATED CODE - DO NOT MODIFY BY HAND')
+      ..writeln()
+      ..writeln('part of $partOf;')
+      ..writeln()
+      ..writeln(_headerLine)
+      ..writeln('// OverReactBuilder (package:over_react/src/builder.dart)')
+      ..writeln(_headerLine);
+
+    for (final item in outputs) {
+      buffer
+        ..writeln()
+        ..writeln(item);
+    }
+
+    final output = _formatter.format(buffer.toString());
+    await buildStep.writeAsString(outputId, output);
+  }
+}

lib/src/builder/util.dart

@@ -1,6 +1,6 @@
 import 'dart:mirrors';
 
-import 'package:analyzer/analyzer.dart';
+import 'package:analyzer/dart/ast/ast.dart';
 import 'package:path/path.dart' as p;
 import 'package:build/build.dart' show AssetId;
 import 'package:source_span/source_span.dart';
@@ -28,6 +28,10 @@ Uri idToPackageUri(AssetId id) {
       path: p.url.join(id.package, id.path.replaceFirst('lib/', '')));
 }
 
+/// Returns true if the given compilation unit is a part file.
+bool isPart(CompilationUnit unit) =>
+    unit.directives.any((directive) => directive is PartOfDirective);
+
 /// Returns a string representing a [TypeParameterList], but type bounds removed.
 ///
 /// Example: