[BUG][CORE] Fix #18963: stop reusing anonymous inline schemas across different parent schemas

docs/customization.md

@@ -532,6 +532,8 @@ Another useful option is `inlineSchemaOptions`, which allows you to customize ho
 - `REFACTOR_ALLOF_INLINE_SCHEMAS=true` will restore the 6.x (or below) behaviour to refactor allOf inline schemas into $ref. (v7.0.0 will skip the refactoring of these allOf inline schemas by default)
 - `RESOLVE_INLINE_ENUMS=true` will refactor inline enum definitions into $ref. This must be activated to allow the renaming of inline enum definitions using `inlineSchemaNameMappings`.
 
+Note: anonymous (untitled) inline schemas are **not** reused across different parent schemas by default (issue #18963). When two parent schemas define structurally identical inline objects without a `title`, each parent gets its own named model (e.g. `Item_user` and `Issue_user`). To have an inline schema reused wherever it appears, add an explicit `title` field — only titled inline schemas are eligible for reuse.
+
 ## OpenAPI Normalizer
 
 OpenAPI Normalizer transforms the input OpenAPI doc/spec (which may not perfectly conform to the specification) to make it workable with OpenAPI Generator. A few rules are switched on by default since 7.0.0 release:

modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java

@@ -853,6 +853,15 @@ private String matchGenerated(Schema model) {
         if (skipSchemaReuse) { // skip reusing schema
             return null;
         }
+        // Only titled schemas represent intentionally shared named types eligible for reuse.
+        // Schemas without a meaningful title have context-derived names (e.g. Item_user) that are
+        // arbitrary — reusing one parent's model for a different parent's structurally-identical
+        // inline schema forces a misleading name onto the other context. "Meaningful title" mirrors
+        // the same check in resolveModelName: non-null and not empty after sanitization.
+        String title = model.getTitle();
+        if (title == null || "".equals(sanitizeName(title).replace("_", ""))) {
+            return null;
+        }
 
         try {
             // Exact content match.

modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java

@@ -3522,22 +3522,24 @@ public void testVarsAndRequiredVarsPresent() {
         assertEquals(co.bodyParams.get(0).vars, vars);
         assertEquals(co.bodyParams.get(0).requiredVars, requiredVars);
 
-        // CodegenOperation puts the inline schema into schemas and refs it
+        // CodegenOperation puts the inline schema into schemas and refs it; the response gets its
+        // own named model since request and response are anonymous schemas in different contexts
         assertTrue(co.responses.get(0).isModel);
-        assertEquals("objectWithOptionalAndRequiredProps_request", co.responses.get(0).baseType);
-        modelName = "objectWithOptionalAndRequiredProps_request";
+        assertEquals("objectWithOptionalAndRequiredProps_200_response", co.responses.get(0).baseType);
+        modelName = "objectWithOptionalAndRequiredProps_200_response";
         sc = openAPI.getComponents().getSchemas().get(modelName);
         cm = codegen.fromModel(modelName, sc);
         assertEquals(cm.vars, vars);
         assertEquals(cm.requiredVars, requiredVars);
 
-        // CodegenProperty puts the inline schema into schemas and refs it
+        // CodegenProperty puts the inline schema into schemas and refs it; anonymous component
+        // inline property gets its own named model derived from parent schema and property name
         modelName = "ObjectPropContainsProps";
         sc = openAPI.getComponents().getSchemas().get(modelName);
         cm = codegen.fromModel(modelName, sc);
         CodegenProperty cp = cm.getVars().get(0);
         assertTrue(cp.isModel);
-        assertEquals("objectWithOptionalAndRequiredProps_request", cp.complexType);
+        assertEquals("ObjectPropContainsProps_a", cp.complexType);
     }
 
     @Test

modules/openapi-generator/src/test/java/org/openapitools/codegen/InlineModelResolverTest.java

@@ -1186,6 +1186,9 @@ public void testInlineSchemaOptions() {
 
     @Test
     public void testInlineSchemaSkipReuseSetToFalse() {
+        // meta_200_response and mega_200_response are anonymous (untitled) inline schemas under
+        // different operations. Anonymous inline schemas are not reused across parents, so both
+        // receive their own named model even though they are structurally identical.
         OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0/inline_model_resolver.yaml");
         InlineModelResolver resolver = new InlineModelResolver();
         Map<String, String> inlineSchemaOptions = new HashMap<>();
@@ -1197,9 +1200,10 @@ public void testInlineSchemaSkipReuseSetToFalse() {
         assertTrue(schema.getProperties().get("name") instanceof StringSchema);
         assertTrue(schema.getProperties().get("id") instanceof IntegerSchema);
 
-        // mega_200_response is NOT created since meta_200_response is reused
         Schema schema2 = openAPI.getComponents().getSchemas().get("mega_200_response");
-        assertNull(schema2);
+        assertNotNull(schema2);
+        assertTrue(schema2.getProperties().get("name") instanceof StringSchema);
+        assertTrue(schema2.getProperties().get("id") instanceof IntegerSchema);
     }
 
     @Test
@@ -1220,6 +1224,86 @@ public void testInlineSchemaSkipReuseSetToTrue() {
         assertTrue(schema2.getProperties().get("id") instanceof IntegerSchema);
     }
 
+    @Test
+    public void resolveAnonymousInlineSchemaNotReusedAcrossParents() {
+        // Two different component schemas (Item, Issue) each define an anonymous (untitled) inline
+        // `user` object with identical members (id, name). Each parent must produce its own named
+        // model; the name from one parent's context must not be imposed on the other.
+        OpenAPI openapi = new OpenAPI();
+        openapi.setComponents(new Components());
+
+        Schema userSchema = new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("name", new StringSchema());
+
+        Schema anotherUserSchema = new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("name", new StringSchema());
+
+        openapi.getComponents().addSchemas("Item", new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("user", userSchema));
+
+        openapi.getComponents().addSchemas("Issue", new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("user", anotherUserSchema));
+
+        new InlineModelResolver().flatten(openapi);
+
+        Map<String, Schema> schemas = openapi.getComponents().getSchemas();
+
+        // Both inline user schemas must exist as separate named models
+        assertNotNull("Item_user model must exist", schemas.get("Item_user"));
+        assertNotNull("Issue_user model must exist", schemas.get("Issue_user"));
+
+        // Item.user must reference its own model
+        Schema itemUser = (Schema) schemas.get("Item").getProperties().get("user");
+        assertEquals("#/components/schemas/Item_user", itemUser.get$ref());
+
+        // Issue.user must reference its own model, not Item_user
+        Schema issueUser = (Schema) schemas.get("Issue").getProperties().get("user");
+        assertEquals("#/components/schemas/Issue_user", issueUser.get$ref());
+    }
+
+    @Test
+    public void resolveTitledInlineSchemaIsReusedAcrossParents() {
+        // A titled inline schema represents a named type that is intentionally shared. When two
+        // different parent schemas each have a property whose inline schema carries the same title
+        // and identical structure, both properties must reference the same named model — only one
+        // entry is created in components, not a numbered variant.
+        OpenAPI openapi = new OpenAPI();
+        openapi.setComponents(new Components());
+
+        openapi.getComponents().addSchemas("Item", new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("user", new ObjectSchema()
+                        .title("UserSummary")
+                        .addProperty("id", new StringSchema().format("uuid"))
+                        .addProperty("name", new StringSchema())));
+
+        openapi.getComponents().addSchemas("Issue", new ObjectSchema()
+                .addProperty("id", new StringSchema().format("uuid"))
+                .addProperty("user", new ObjectSchema()
+                        .title("UserSummary")
+                        .addProperty("id", new StringSchema().format("uuid"))
+                        .addProperty("name", new StringSchema())));
+
+        new InlineModelResolver().flatten(openapi);
+
+        Map<String, Schema> schemas = openapi.getComponents().getSchemas();
+
+        // Titled inline schema must be deduplicated — no numbered variant
+        assertNotNull("UserSummary schema must exist", schemas.get("UserSummary"));
+        assertNull("Duplicate UserSummary_1 must not exist", schemas.get("UserSummary_1"));
+
+        // Both parents must reference the same shared model
+        Schema itemUser = (Schema) schemas.get("Item").getProperties().get("user");
+        assertEquals("#/components/schemas/UserSummary", itemUser.get$ref());
+
+        Schema issueUser = (Schema) schemas.get("Issue").getProperties().get("user");
+        assertEquals("#/components/schemas/UserSummary", issueUser.get$ref());
+    }
+
     @Test
     public void resolveInlineRequestBodyAllOf() {
         OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0/inline_model_resolver.yaml");

samples/client/petstore/R-httr2-wrapper/.openapi-generator/FILES

@@ -5,6 +5,7 @@
 .travis.yml
 DESCRIPTION
 NAMESPACE
+R/add_pet_optional_request.R
 R/allof_tag_api_response.R
 R/animal.R
 R/any_of_pig.R
@@ -40,6 +41,7 @@ R/user_api.R
 R/whale.R
 R/zebra.R
 README.md
+docs/AddPetOptionalRequest.md
 docs/AllofTagApiResponse.md
 docs/Animal.md
 docs/AnyOfPig.md
@@ -72,3 +74,4 @@ docs/Whale.md
 docs/Zebra.md
 git_push.sh
 tests/testthat.R
+tests/testthat/test_add_pet_optional_request.R

samples/client/petstore/R-httr2-wrapper/NAMESPACE

@@ -16,6 +16,7 @@ export(ApiResponse)
 export(ApiException)
 
 # Models
+export(AddPetOptionalRequest)
 export(AllofTagApiResponse)
 export(Animal)
 export(AnyOfPig)