Fix schema filtering for parameter references

swagger_parser/lib/src/parser/parser/open_api_parser.dart

@@ -267,10 +267,17 @@ class OpenApiParser {
           }
           final isRequired =
               parameter[_requiredConst]?.toString().toBool() ?? false;
+          final parameterSchema = parameter[_schemaConst] != null
+              ? parameter[_schemaConst] as Map<String, dynamic>
+              : parameter;
+
+          // Query/path/header parameters may reference component schemas.
+          // Register those references so tag-based schema filtering does not
+          // discard models used only by parameters.
+          _extractSchemaRefs(parameterSchema, null);
+
           final typeWithImport = _findType(
-            parameter[_schemaConst] != null
-                ? parameter[_schemaConst] as Map<String, dynamic>
-                : parameter,
+            parameterSchema,
             name: parameter[_nameConst].toString(),
             isRequired: isRequired,
           );
@@ -549,10 +556,15 @@ class OpenApiParser {
               as Map<String, dynamic>;
         }
 
+        final parameterSchema = parameter[_schemaConst] != null
+            ? parameter[_schemaConst] as Map<String, dynamic>
+            : parameter;
+
+        // Keep component schemas referenced by parameters when filtering.
+        _extractSchemaRefs(parameterSchema, null);
+
         final typeWithImport = _findType(
-          rawParameter[_schemaConst] != null
-              ? rawParameter[_schemaConst] as Map<String, dynamic>
-              : rawParameter,
+          parameterSchema,
           name: rawParameter[_nameConst].toString(),
           isRequired: isRequired,
         );

swagger_parser/test/parser/parameter_schema_filtering_test.dart

@@ -0,0 +1,57 @@
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:swagger_parser/swagger_parser.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('keeps schemas referenced by filtered endpoint parameters', () async {
+    final root = await Directory.systemTemp.createTemp('swagger-parser-test-');
+    addTearDown(() => root.delete(recursive: true));
+
+    final schema = File(p.join(root.path, 'openapi.yaml'))
+      ..writeAsStringSync(r'''
+openapi: 3.0.0
+info:
+  title: Parameter schema filtering
+  version: 1.0.0
+paths:
+  /public:
+    get:
+      tags: [public]
+      parameters:
+        - name: unit
+          in: query
+          schema:
+            $ref: '#/components/schemas/Unit'
+      responses:
+        '200':
+          description: OK
+  /admin:
+    get:
+      tags: [admin]
+      responses:
+        '200':
+          description: OK
+components:
+  schemas:
+    Unit:
+      type: string
+      enum: [imperial, metric]
+''');
+
+    await GenProcessor(
+      SWPConfig(
+        schemaPath: schema.path,
+        outputDirectory: p.join(root.path, 'generated'),
+        excludeTags: ['admin'],
+        putClientsInFolder: true,
+      ),
+    ).generateFiles();
+
+    expect(
+      File(p.join(root.path, 'generated', 'models', 'unit.dart')).existsSync(),
+      isTrue,
+    );
+  });
+}