fix: resolve refs within external schemas

modules/swagger-parser-v3/src/main/java/io/swagger/v3/parser/reference/OpenAPI31Traverser.java

@@ -794,6 +794,9 @@ public Schema traverseSchema(Schema schema, ReferenceVisitor visitor, List<Strin
                     resolvedURI = ReferenceUtils.toBaseURI(resolvedURI);
                 }
                 context.getIdsCache().put(resolvedURI, Json31.pretty(schema));
+                if (!visitor.reference.getReferenceSet().containsKey(resolvedURI)) {
+                    visitor.reference.getReferenceSet().put(resolvedURI, visitor.reference);
+                }
             } catch (Exception e) {
                //
             }
@@ -920,6 +923,9 @@ public Schema traverseSchema(Schema schema, ReferenceVisitor visitor, List<Strin
             visiting.remove(schema);
             return handleRootLocalRefs(schema.get$ref(), resolved, context.getOpenApi().getComponents().getSchemas());
         }
+        if (resolvedNotNull && schema.getProperties() != null && !schema.getProperties().isEmpty()) {
+            traverseSchemaMap(schema.getProperties(), visitor, inheritedIds);
+        }
         // merge ALL STUFF
         mergeSchemas(schema, resolved);
         visitedMap.put(schema, deepcopy(resolved, Schema.class));

modules/swagger-parser-v3/src/test/java/io/swagger/v3/parser/test/OpenAPIV31ParserSchemaTest.java

@@ -153,6 +153,14 @@ private void setUpWireMockServer() throws IOException {
                         .withBody(pathFile
                                 .getBytes(StandardCharsets.UTF_8))));
 
+        pathFile = FileUtils.readFileToString(new File("src/test/resources/3.1.0/dereference/schema/external-oas-with-id-defs/oas.yaml"), StandardCharsets.UTF_8);
+
+        WireMock.stubFor(get(urlPathMatching("/oai-v3.1-schema.yaml"))
+                .willReturn(aResponse()
+                        .withStatus(HttpURLConnection.HTTP_OK)
+                        .withHeader("Content-type", "application/yaml")
+                        .withBody(pathFile.getBytes(StandardCharsets.UTF_8))));
+
     }
 
     @AfterClass
@@ -216,6 +224,25 @@ public void testAnchorUnresolve() throws Exception {
         compare("$anchor-not-found", swaggerParseResult);
     }
 
+    @Test
+    public void testExternalSchemaWithIdAndDefsResolution_issue2271() throws IOException {
+        String rootYaml = FileUtils.readFileToString(
+                new File("src/test/resources/3.1.0/dereference/schema/external-oas-with-id-defs/root.yaml"),
+                StandardCharsets.UTF_8);
+        rootYaml = rootYaml.replace("${dynamicPort}", String.valueOf(this.serverPort));
+
+        ParseOptions options = new ParseOptions();
+        options.setResolve(true);
+        SwaggerParseResult result = new OpenAPIV3Parser().readContents(rootYaml, null, options);
+
+        org.testng.Assert.assertNotNull(result.getOpenAPI());
+        org.testng.Assert.assertTrue(
+                result.getMessages() == null
+                        || result.getMessages().stream().noneMatch(m -> m.contains("Could not find /$defs")),
+                "Expected no $defs resolution errors when resolving external schema with $id, but got: "
+                        + result.getMessages());
+    }
+
     public void compare(String dir, SwaggerParseResult result) throws Exception {
         ObjectMapper mapper = Json31.mapper().copy();
         mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);

modules/swagger-parser-v3/src/test/resources/3.1.0/dereference/schema/external-oas-with-id-defs/oas.yaml

@@ -0,0 +1,29 @@
+$id: 'https://spec.openapis.org/oas/3.1/schema/2022-10-07'
+$schema: 'https://json-schema.org/draft/2020-12/schema'
+type: object
+properties:
+  info:
+    $ref: '#/$defs/info'
+  servers:
+    type: array
+    items:
+      $ref: '#/$defs/server'
+$ref: '#/$defs/extensions'
+$defs:
+  info:
+    type: object
+    properties:
+      title:
+        type: string
+    required:
+      - title
+  server:
+    type: object
+    properties:
+      url:
+        type: string
+    required:
+      - url
+  extensions:
+    patternProperties:
+      '^x-': true

modules/swagger-parser-v3/src/test/resources/3.1.0/dereference/schema/external-oas-with-id-defs/root.yaml

@@ -0,0 +1,31 @@
+openapi: 3.1.0
+info:
+  title: Test external OAI schema with $id and $defs resolution
+  version: 1.0.0
+paths:
+  /hello:
+    get:
+      operationId: hello
+      responses:
+        "200":
+          description: A successful response
+          $ref: '#/components/responses/Data'
+components:
+  responses:
+    Data:
+      description: Description of the response
+      content:
+        application/json:
+          schema:
+            type: object
+            required:
+              - items
+            properties:
+              items:
+                message:
+                  type: string
+              schema:
+                $ref: "#/components/schemas/OpenApiSchema"
+  schemas:
+    OpenApiSchema:
+      $ref: "http://localhost:${dynamicPort}/oai-v3.1-schema.yaml"