[pigeon] Adds platform for imports that aren't support on a platform (#…

…8338)

While working on updating `webview_flutter_wkwebview` to use ProxyApis, the `UIKit` import would be invalid on macOS. This PR now surrounds `ProxyApi` imports with a check if every class of an import excludes a platform.

packages/pigeon/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 22.7.1
 
+* [swift] Adds support for platform checks of imports of ProxyApis.
 * Updates minimum supported SDK version to Flutter 3.22/Dart 3.4.
 
 ## 22.7.0

packages/pigeon/lib/generator_tools.dart

@@ -14,7 +14,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '22.7.0';
+const String pigeonVersion = '22.7.1';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {

packages/pigeon/lib/swift_generator.dart

@@ -154,14 +154,7 @@ class SwiftGenerator extends StructuredGenerator<SwiftOptions> {
   }) {
     indent.writeln('import Foundation');
 
-    final Iterable<String> proxyApiImports = root.apis
-        .whereType<AstProxyApi>()
-        .map((AstProxyApi proxyApi) => proxyApi.swiftOptions?.import)
-        .nonNulls
-        .toSet();
-    for (final String import in proxyApiImports) {
-      indent.writeln('import $import');
-    }
+    _writeProxyApiImports(indent, root.apis.whereType<AstProxyApi>());
     indent.newln();
 
     indent.format('''
@@ -2487,6 +2480,42 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
       });
     });
   }
+
+  void _writeProxyApiImports(Indent indent, Iterable<AstProxyApi> apis) {
+    final Map<String, List<AstProxyApi>> apisOfImports =
+        <String, List<AstProxyApi>>{};
+    for (final AstProxyApi proxyApi in apis) {
+      final String? import = proxyApi.swiftOptions?.import;
+      if (import != null) {
+        if (apisOfImports.containsKey(import)) {
+          apisOfImports[import]!.add(proxyApi);
+        } else {
+          apisOfImports[import] = <AstProxyApi>[proxyApi];
+        }
+      }
+    }
+
+    for (final String import in apisOfImports.keys) {
+      // If every ProxyApi that shares an import excludes a platform for
+      // support, surround the import with `#if !os(...) #endif`.
+      final List<String> unsupportedPlatforms = <String>[
+        if (!apisOfImports[import]!
+            .any((AstProxyApi api) => api.swiftOptions?.supportsIos ?? true))
+          '!os(iOS)',
+        if (!apisOfImports[import]!
+            .any((AstProxyApi api) => api.swiftOptions?.supportsMacos ?? true))
+          '!os(macOS)',
+      ];
+
+      if (unsupportedPlatforms.isNotEmpty) {
+        indent.writeln('#if ${unsupportedPlatforms.join(' || ')}');
+      }
+      indent.writeln('import $import');
+      if (unsupportedPlatforms.isNotEmpty) {
+        indent.writeln('#endif');
+      }
+    }
+  }
 }
 
 typedef _VersionRequirement = ({TypeDeclaration type, Version version});

packages/pigeon/pubspec.yaml

@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 22.7.0 # This must match the version in lib/generator_tools.dart
+version: 22.7.1 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ^3.4.0

packages/pigeon/test/swift/proxy_api_test.dart

@@ -187,6 +187,141 @@ void main() {
       );
     });
 
+    group('imports', () {
+      test('add check if every class does not support iOS', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              swiftOptions: const SwiftProxyApiOptions(
+                import: 'MyImport',
+                supportsIos: false,
+              ),
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const SwiftGenerator generator = SwiftGenerator();
+        generator.generate(
+          const SwiftOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+
+        expect(code, contains('#if !os(iOS)\nimport MyImport\n#endif'));
+      });
+
+      test('add check if every class does not support macOS', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              swiftOptions: const SwiftProxyApiOptions(
+                import: 'MyImport',
+                supportsMacos: false,
+              ),
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const SwiftGenerator generator = SwiftGenerator();
+        generator.generate(
+          const SwiftOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+
+        expect(code, contains('#if !os(macOS)\nimport MyImport\n#endif'));
+      });
+
+      test('add check if for multiple unsupported platforms', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              swiftOptions: const SwiftProxyApiOptions(
+                import: 'MyImport',
+                supportsIos: false,
+                supportsMacos: false,
+              ),
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const SwiftGenerator generator = SwiftGenerator();
+        generator.generate(
+          const SwiftOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+
+        expect(
+          code,
+          contains('#if !os(iOS) || !os(macOS)\nimport MyImport\n#endif'),
+        );
+      });
+
+      test('do not add check if at least one class is supported', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              swiftOptions: const SwiftProxyApiOptions(
+                import: 'MyImport',
+                supportsIos: false,
+              ),
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+            AstProxyApi(
+              name: 'Api2',
+              swiftOptions: const SwiftProxyApiOptions(
+                import: 'MyImport',
+              ),
+              constructors: <Constructor>[],
+              fields: <ApiField>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const SwiftGenerator generator = SwiftGenerator();
+        generator.generate(
+          const SwiftOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+
+        expect(code, isNot(contains('#if !os(iOS)\nimport MyImport')));
+      });
+    });
+
     group('inheritance', () {
       test('extends', () {
         final AstProxyApi api2 = AstProxyApi(