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Add LazyMergedMap for merging Model objects (#105)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| // Copyright (c) 2024, 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. | ||
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| import 'dart:collection'; | ||
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| import 'dart_model.dart'; | ||
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| /// An implementation of a lazy merged json [Map] view over two [Map]s. | ||
| /// | ||
| /// The intended use case is for merging JSON payloads together into a single | ||
| /// payload, where their structure is the same. | ||
| /// | ||
| /// If both maps have the same key present, the logic for the values of those | ||
| /// shared keys goes as follows: | ||
| /// | ||
| /// - If both values are `Map<String, Object?>`, a nested [LazyMergedMapView] | ||
| /// is returned. | ||
| /// - Else if they are equal values, the value from [left] is returned. | ||
| /// - Else a [StateError] is thrown. | ||
| /// | ||
| /// Nested [List]s are not specifically handled at this time and must be equal. | ||
| /// | ||
| /// The [keys] getter will de-duplicate the keys. | ||
| class LazyMergedMapView extends MapBase<String, Object?> { | ||
| final Map<String, Object?> left; | ||
| final Map<String, Object?> right; | ||
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| LazyMergedMapView(this.left, this.right); | ||
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| @override | ||
| Object? operator [](Object? key) { | ||
| // TODO: Can we do better? These lookups can each be linear for buffer maps. | ||
| var leftValue = left[key]; | ||
| var rightValue = right[key]; | ||
| if (leftValue != null) { | ||
| if (rightValue != null) { | ||
| if (leftValue is Map<String, Object?> && | ||
| rightValue is Map<String, Object?>) { | ||
| return LazyMergedMapView(leftValue, rightValue); | ||
| } | ||
| if (leftValue != rightValue) { | ||
| throw StateError('Cannot merge maps with different values, and ' | ||
| '$leftValue != $rightValue'); | ||
| } | ||
| return leftValue; | ||
| } | ||
| return leftValue; | ||
| } else if (rightValue != null) { | ||
| return rightValue; | ||
| } | ||
| return null; | ||
| } | ||
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| @override | ||
| void operator []=(String key, Object? value) => | ||
| throw UnsupportedError('Merged maps are read only'); | ||
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| @override | ||
| void clear() => throw UnsupportedError('Merged maps are read only'); | ||
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| @override | ||
| Iterable<String> get keys sync* { | ||
| var seen = <String>{}; | ||
| for (var key in left.keys.followedBy(right.keys)) { | ||
| if (seen.add(key)) yield key; | ||
| } | ||
| } | ||
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| @override | ||
| Object? remove(Object? key) => | ||
| throw UnsupportedError('Merged maps are read only'); | ||
| } | ||
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| extension AllMaps on Map<String, Object?> { | ||
| /// All the maps merged into this map, recursively expanded. | ||
| Iterable<Map<String, Object?>> get expand sync* { | ||
| if (this case final LazyMergedMapView self) { | ||
| yield* self.left.expand; | ||
| yield* self.right.expand; | ||
| } else { | ||
| yield this; | ||
| } | ||
| } | ||
| } | ||
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| extension MergeModels on Model { | ||
| /// Creates a lazy merged view of `this` with [other]. | ||
| Model mergeWith(Model other) => | ||
| Model.fromJson(LazyMergedMapView(node, other.node)); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,66 @@ | ||
| // Copyright (c) 2024, 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. | ||
|
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| import 'package:dart_model/dart_model.dart'; | ||
| import 'package:dart_model/src/lazy_merged_map.dart'; | ||
| import 'package:test/test.dart' hide test; | ||
| import 'package:test/test.dart' as t show test; | ||
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| void main() { | ||
| test('Can merge models with different libraries', () async { | ||
| final libA = Library(); | ||
| final libB = Library(); | ||
| final a = Model()..uris['package:a/a.dart'] = libA; | ||
| final b = Model()..uris['package:b/b.dart'] = libB; | ||
| final c = a.mergeWith(b); | ||
| expect(c.uris['package:a/a.dart'], libA); | ||
| expect(c.uris['package:b/b.dart'], libB); | ||
| }); | ||
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| test('Can merge models with different scopes from the same library', | ||
| () async { | ||
| final interfaceA = Interface(); | ||
| final interfaceB = Interface(); | ||
| final a = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['A'] = interfaceA); | ||
| final b = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['B'] = interfaceB); | ||
| final c = a.mergeWith(b); | ||
| expect(c.uris['package:a/a.dart'], isA<LazyMergedMapView>()); | ||
| expect(c.uris['package:a/a.dart']!.scopes['A'], interfaceA); | ||
| expect(c.uris['package:a/a.dart']!.scopes['B'], interfaceB); | ||
| }); | ||
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| test('Can merge models with the same interface but different properties', | ||
| () async { | ||
| final interfaceA1 = Interface(properties: Properties(isClass: true)); | ||
| final interfaceA2 = Interface(properties: Properties(isAbstract: true)); | ||
| final a = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['A'] = interfaceA1); | ||
| final b = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['A'] = interfaceA2); | ||
| final c = a.mergeWith(b); | ||
| final properties = c.uris['package:a/a.dart']!.scopes['A']!.properties; | ||
| expect(properties, isA<LazyMergedMapView>()); | ||
| expect(properties.isClass, true); | ||
| expect(properties.isAbstract, true); | ||
| // Not set | ||
| expect(() => properties.isConstructor, throwsA(isA<TypeError>())); | ||
| }); | ||
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| test('Errors if maps have same the key with different values', () async { | ||
| final interfaceA1 = Interface(properties: Properties(isClass: true)); | ||
| final interfaceA2 = Interface(properties: Properties(isClass: false)); | ||
| final a = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['A'] = interfaceA1); | ||
| final b = Model() | ||
| ..uris['package:a/a.dart'] = (Library()..scopes['A'] = interfaceA2); | ||
| final c = a.mergeWith(b); | ||
| expect(() => c.uris['package:a/a.dart']!.scopes['A']!.properties.isClass, | ||
| throwsA(isA<StateError>())); | ||
| }); | ||
| } | ||
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| void test(String description, void Function() body) => | ||
| t.test(description, () => Scope.query.run(body)); |
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