Support for SDK constraints

Author: alexei-sintotski

lib/src/internal/load_from_yaml.dart

@@ -57,6 +57,9 @@ PubspecYaml loadFromYaml(String content) {
     dependencies: _loadDependenciesIfRequired(jsonMap, Tokens.dependencies),
     devDependencies: _loadDependenciesIfRequired(jsonMap, Tokens.devDependencies),
     dependencyOverrides: _loadDependenciesIfRequired(jsonMap, Tokens.dependencyOverrides),
+    environment: jsonMap.containsKey(Tokens.environment) && jsonMap[Tokens.environment] != null
+        ? _loadEnvironment(jsonMap[Tokens.environment] as Map<String, dynamic>)
+        : {},
     executables: jsonMap.containsKey(Tokens.executables) && jsonMap[Tokens.executables] != null
         ? _loadExecutables(jsonMap[Tokens.executables] as Map<String, dynamic>)
         : {},
@@ -129,6 +132,9 @@ HostedPackageDependencySpec _loadGenericHostedDependency(String package, Map<Str
   );
 }
 
+Map<String, String> _loadEnvironment(Map<String, dynamic> environment) =>
+    environment.map((key, dynamic value) => MapEntry(key, value as String));
+
 Map<String, Optional<String>> _loadExecutables(Map<String, dynamic> executables) =>
     executables.map((key, dynamic value) => MapEntry(
           key,
@@ -149,4 +155,5 @@ const _knownTokens = [
   Tokens.executables,
   Tokens.devDependencies,
   Tokens.dependencyOverrides,
+  Tokens.environment,
 ];

lib/src/internal/tokens.dart

@@ -42,4 +42,5 @@ class Tokens {
   static const executables = 'executables';
   static const devDependencies = 'dev_dependencies';
   static const dependencyOverrides = 'dependency_overrides';
+  static const environment = 'environment';
 }

lib/src/internal/yaml_formatter.dart

@@ -40,6 +40,7 @@ String formatToYaml(PubspecYaml pubspecYaml) => '${[
         _dependenciesToYaml(pubspecYaml.devDependencies, Tokens.devDependencies),
       if (pubspecYaml.dependencyOverrides.isNotEmpty)
         _dependenciesToYaml(pubspecYaml.dependencyOverrides, Tokens.dependencyOverrides),
+      if (pubspecYaml.environment.isNotEmpty) _environmentToYaml(pubspecYaml.environment),
       if (pubspecYaml.executables.isNotEmpty) _executablesToYaml(pubspecYaml.executables),
       for (final customField in pubspecYaml.customFields.entries)
         json2yaml(Map<String, dynamic>.fromEntries({customField}), yamlStyle: YamlStyle.pubspecYaml),
@@ -111,6 +112,11 @@ MapEntry<String, dynamic> _hostedPackageDependencyToJson(HostedPackageDependency
           : dep.version.valueOr(() => null),
     );
 
+String _environmentToYaml(Map<String, String> environment) => json2yaml(
+      <String, dynamic>{Tokens.environment: environment},
+      yamlStyle: YamlStyle.pubspecYaml,
+    );
+
 String _executablesToYaml(Map<String, Optional<String>> executables) => json2yaml(
       <String, dynamic>{
         Tokens.executables: <String, dynamic>{

lib/src/pubspec_yaml.dart

@@ -57,6 +57,7 @@ class PubspecYaml extends $PubspecYaml {
     this.dependencies = const [],
     this.devDependencies = const [],
     this.dependencyOverrides = const [],
+    this.environment = const {},
     this.executables = const {},
     this.customFields = const <String, dynamic>{},
   });
@@ -112,6 +113,11 @@ class PubspecYaml extends $PubspecYaml {
   @CustomEquality(DeepCollectionEquality())
   final Iterable<PackageDependencySpec> dependencyOverrides;
 
+  /// SDK constraints
+  /// https://dart.dev/tools/pub/pubspec#sdk-constraints
+  @CustomEquality(DeepCollectionEquality())
+  final Map<String, String> environment;
+
   /// Executables that can be run directly from the command line
   /// https://dart.dev/tools/pub/pubspec#executables
   @CustomEquality(DeepCollectionEquality())

lib/src/pubspec_yaml.g.dart

@@ -0,0 +1,67 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 Alexei Sintotski
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+import 'package:pubspec_yaml/pubspec_yaml.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('given pubspec.yaml with SDK constraints', () {
+    final pubspecYaml = PubspecYaml.loadFromYamlString(pubspecYamlWithSdkConstraints);
+
+    group('$PubspecYaml.loadFromYamlString()', () {
+      test('provides object with non-empty environment', () {
+        expect(pubspecYaml.environment, isNotEmpty);
+      });
+      test('provides object correct SDK names', () {
+        expect(pubspecYaml.environment.keys, [dartSdk, flutterSdk]);
+      });
+      test('provides object correct SDK entries', () {
+        expect(pubspecYaml.environment[dartSdk], dartSdkConstraint);
+        expect(pubspecYaml.environment[flutterSdk], flutterSdkConstraint);
+      });
+      test('provides object without custom fields', () {
+        expect(pubspecYaml.customFields, isEmpty);
+      });
+    });
+
+    group('$PubspecYaml.toYamlString()', () {
+      test('produces output identical to the original string', () {
+        expect(pubspecYaml.toYamlString(), pubspecYamlWithSdkConstraints);
+      });
+    });
+  });
+}
+
+const dartSdk = 'sdk';
+const dartSdkConstraint = '>=1.19.0 <3.0.0';
+const flutterSdk = 'flutter';
+const flutterSdkConstraint = '^0.1.2';
+const pubspecYamlWithSdkConstraints = '''
+name: pubspec_yaml
+
+environment:
+  $dartSdk: "$dartSdkConstraint"
+  $flutterSdk: $flutterSdkConstraint
+''';