More work towards feature parity of 1x (#116)

* WIP.

* Finish up feature parity.

* Dartfmt.

* Address feedback.

* Format with dart_style:format for now.

* Fix tests.

Author: matanlurey

lib/code_builder.dart

@@ -2,14 +2,18 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+export 'src/allocator.dart' show Allocator;
 export 'src/base.dart' show Spec;
 export 'src/emitter.dart' show DartEmitter;
 export 'src/matchers.dart' show equalsDart;
 export 'src/specs/annotation.dart' show Annotation, AnnotationBuilder;
 export 'src/specs/class.dart' show Class, ClassBuilder;
 export 'src/specs/code.dart' show Code, CodeBuilder;
 export 'src/specs/constructor.dart' show Constructor, ConstructorBuilder;
+export 'src/specs/directive.dart'
+    show Directive, DirectiveType, DirectiveBuilder;
 export 'src/specs/field.dart' show Field, FieldBuilder, FieldModifier;
+export 'src/specs/file.dart' show File, FileBuilder;
 export 'src/specs/method.dart'
     show Method, MethodBuilder, MethodType, Parameter, ParameterBuilder;
 export 'src/specs/reference.dart' show Reference;

lib/src/allocator.dart

@@ -0,0 +1,95 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'specs/directive.dart';
+import 'specs/reference.dart';
+
+/// Collects references and automatically allocates prefixes and imports.
+///
+/// `Allocator` takes out the manual work of deciding whether a symbol will
+/// clash with other imports in your generated code, or what imports are needed
+/// to resolve all symbols in your generated code.
+abstract class Allocator {
+  /// An allocator that does not prefix symbols nor collects imports.
+  static const Allocator none = const _NullAllocator();
+
+  /// Creates a new default allocator that applies no prefixing.
+  factory Allocator() = _Allocator;
+
+  /// Creates a new allocator that applies naive prefixing to avoid conflicts.
+  ///
+  /// This implementation is not optimized for any particular code generation
+  /// style and instead takes a conservative approach of prefixing _every_
+  /// import except references to `dart:core` (which are considered always
+  /// imported).
+  factory Allocator.simplePrefixing() = _PrefixedAllocator;
+
+  /// Returns a reference string given a [reference] object.
+  ///
+  /// For example, a no-op implementation:
+  /// ```dart
+  /// allocate(const Reference('List', 'dart:core')); // Returns 'List'.
+  /// ```
+  ///
+  /// Where-as an implementation that prefixes imports might output:
+  /// ```dart
+  /// allocate(const Reference('Foo', 'package:foo')); // Returns '_i1.Foo'.
+  /// ```
+  String allocate(Reference reference);
+
+  /// All imports that have so far been added implicitly via [allocate].
+  Iterable<Directive> get imports;
+}
+
+class _Allocator implements Allocator {
+  final _imports = new Set<String>();
+
+  @override
+  String allocate(Reference reference) {
+    if (reference.url != null) {
+      _imports.add(reference.url);
+    }
+    return reference.symbol;
+  }
+
+  @override
+  Iterable<Directive> get imports {
+    return _imports.map((u) => new Directive.import(u));
+  }
+}
+
+class _NullAllocator implements Allocator {
+  const _NullAllocator();
+
+  @override
+  String allocate(Reference reference) => reference.symbol;
+
+  @override
+  Iterable<Directive> get imports => const [];
+}
+
+class _PrefixedAllocator implements Allocator {
+  static const _doNotPrefix = const ['dart:core'];
+
+  final _imports = <String, int>{};
+  var _keys = 1;
+
+  @override
+  String allocate(Reference reference) {
+    final symbol = reference.symbol;
+    if (reference.url == null || _doNotPrefix.contains(reference.url)) {
+      return symbol;
+    }
+    return '_${_imports.putIfAbsent(reference.url, _nextKey)}.$symbol';
+  }
+
+  int _nextKey() => _keys++;
+
+  @override
+  Iterable<Directive> get imports {
+    return _imports.keys.map(
+      (u) => new Directive.import(u, as: '_${_imports[u]}'),
+    );
+  }
+}

lib/src/emitter.dart

@@ -2,18 +2,30 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'allocator.dart';
+import 'base.dart';
 import 'specs/annotation.dart';
 import 'specs/class.dart';
 import 'specs/code.dart';
 import 'specs/constructor.dart';
+import 'specs/directive.dart';
 import 'specs/field.dart';
+import 'specs/file.dart';
 import 'specs/method.dart';
 import 'specs/reference.dart';
 import 'specs/type_reference.dart';
 import 'visitors.dart';
 
-class DartEmitter extends GeneralizingSpecVisitor<StringSink> {
-  const DartEmitter();
+class DartEmitter implements SpecVisitor<StringSink> {
+  final Allocator _allocator;
+
+  /// Creates a new instance of [DartEmitter].
+  ///
+  /// May specify an [Allocator] to use for symbols, otherwise uses a no-op.
+  const DartEmitter([this._allocator = Allocator.none]);
+
+  /// Creates a new instance of [DartEmitter] with a default [Allocator].
+  factory DartEmitter.scoped() => new DartEmitter(new Allocator());
 
   @override
   visitAnnotation(Annotation spec, [StringSink output]) {
@@ -154,6 +166,22 @@ class DartEmitter extends GeneralizingSpecVisitor<StringSink> {
     return output..write(code);
   }
 
+  @override
+  visitDirective(Directive spec, [StringSink output]) {
+    output ??= new StringBuffer();
+    if (spec.type == DirectiveType.import) {
+      output.write('import ');
+    } else {
+      output.write('export ');
+    }
+    output.write("'${spec.url}'");
+    if (spec.as != null) {
+      output.write(' as ${spec.as}');
+    }
+    output.write(';');
+    return output;
+  }
+
   @override
   visitField(Field spec, [StringSink output]) {
     output ??= new StringBuffer();
@@ -188,6 +216,25 @@ class DartEmitter extends GeneralizingSpecVisitor<StringSink> {
     return output;
   }
 
+  @override
+  visitFile(File spec, [StringSink output]) {
+    output ??= new StringBuffer();
+    // Process the body first in order to prime the allocators.
+    final body = new StringBuffer();
+    for (final spec in spec.body) {
+      body.write(visitSpec(spec));
+    }
+    // TODO: Allow some sort of logical ordering.
+    for (final directive in spec.directives) {
+      visitDirective(directive, output);
+    }
+    for (final directive in _allocator.imports) {
+      visitDirective(directive, output);
+    }
+    output.write(body);
+    return output;
+  }
+
   @override
   visitMethod(Method spec, [StringSink output]) {
     output ??= new StringBuffer();
@@ -293,9 +340,12 @@ class DartEmitter extends GeneralizingSpecVisitor<StringSink> {
 
   @override
   visitReference(Reference spec, [StringSink output]) {
-    return (output ??= new StringBuffer())..write(spec.symbol);
+    return (output ??= new StringBuffer())..write(_allocator.allocate(spec));
   }
 
+  @override
+  visitSpec(Spec spec) => spec.accept(this);
+
   @override
   visitType(TypeReference spec, [StringSink output]) {
     output ??= new StringBuffer();

lib/src/matchers.dart

@@ -22,16 +22,21 @@ String _dartfmt(String source) {
 }
 
 /// Encodes [spec] as Dart source code.
-String _dart(Spec spec) =>
-    _dartfmt(spec.accept<StringSink>(const DartEmitter()).toString());
+String _dart(Spec spec, DartEmitter emitter) =>
+    _dartfmt(spec.accept<StringSink>(emitter).toString()).trim();
 
 /// Returns a matcher for Dart source code.
-Matcher equalsDart(String source) => new _EqualsDart(_dartfmt(source));
+Matcher equalsDart(
+  String source, [
+  DartEmitter emitter = const DartEmitter(),
+]) =>
+    new _EqualsDart(_dartfmt(source).trim(), emitter);
 
 class _EqualsDart extends Matcher {
+  final DartEmitter _emitter;
   final String _source;
 
-  const _EqualsDart(this._source);
+  const _EqualsDart(this._source, this._emitter);
 
   @override
   Description describe(Description description) => description.add(_source);
@@ -40,11 +45,18 @@ class _EqualsDart extends Matcher {
   Description describeMismatch(
     covariant Spec item,
     Description mismatchDescription,
-    _,
-    __,
-  ) =>
-      mismatchDescription.add(_dart(item));
+    state,
+    verbose,
+  ) {
+    final result = _dart(item, _emitter);
+    return equals(result).describeMismatch(
+      _source,
+      mismatchDescription,
+      state,
+      verbose,
+    );
+  }
 
   @override
-  bool matches(covariant Spec item, _) => _dart(item) == _source;
+  bool matches(covariant Spec item, _) => _dart(item, _emitter) == _source;
 }

lib/src/specs/directive.dart

@@ -0,0 +1,61 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library code_builder.src.specs.directive;
+
+import 'package:built_value/built_value.dart';
+import 'package:meta/meta.dart';
+
+import '../base.dart';
+import '../visitors.dart';
+
+part 'directive.g.dart';
+
+@immutable
+abstract class Directive implements Built<Directive, DirectiveBuilder>, Spec {
+  factory Directive([void updates(DirectiveBuilder b)]) = _$Directive;
+
+  factory Directive.import(
+    String url, {
+    String as,
+  }) =>
+      new Directive((builder) => builder
+        ..as = as
+        ..type = DirectiveType.import
+        ..url = url);
+
+  factory Directive.export(String url) => new Directive((builder) => builder
+    ..type = DirectiveType.export
+    ..url = url);
+
+  Directive._();
+
+  @nullable
+  String get as;
+
+  String get url;
+
+  DirectiveType get type;
+
+  @override
+  R accept<R>(SpecVisitor<R> visitor) => visitor.visitDirective(this);
+}
+
+abstract class DirectiveBuilder
+    implements Builder<Directive, DirectiveBuilder> {
+  factory DirectiveBuilder() = _$DirectiveBuilder;
+
+  DirectiveBuilder._();
+
+  String as;
+
+  String url;
+
+  DirectiveType type;
+}
+
+enum DirectiveType {
+  import,
+  export,
+}