[python] reserve generated helper and pydantic model_* property names

docs/generators/python.md

@@ -101,6 +101,8 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 <li>for</li>
 <li>form_params</li>
 <li>from</li>
+<li>from_dict</li>
+<li>from_json</li>
 <li>global</li>
 <li>header_params</li>
 <li>if</li>
@@ -110,6 +112,22 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 <li>json</li>
 <li>lambda</li>
 <li>local_var_files</li>
+<li>model_computed_fields</li>
+<li>model_config</li>
+<li>model_construct</li>
+<li>model_copy</li>
+<li>model_dump</li>
+<li>model_dump_json</li>
+<li>model_extra</li>
+<li>model_fields</li>
+<li>model_fields_set</li>
+<li>model_json_schema</li>
+<li>model_parametrized_name</li>
+<li>model_post_init</li>
+<li>model_rebuild</li>
+<li>model_validate</li>
+<li>model_validate_json</li>
+<li>model_validate_strings</li>
 <li>none</li>
 <li>nonlocal</li>
 <li>not</li>
@@ -124,6 +142,9 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 <li>return</li>
 <li>schema</li>
 <li>self</li>
+<li>to_dict</li>
+<li>to_json</li>
+<li>to_str</li>
 <li>true</li>
 <li>try</li>
 <li>while</li>

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

@@ -151,6 +151,17 @@ public PythonClientCodegen() {
                 .stability(Stability.STABLE)
                 .build();
 
+        // fields with these names would clash with the helper methods generated on every
+        // model (a field named from_dict shadows the classmethod) or with pydantic's
+        // model_* namespace (a field named model_config is clobbered by the ConfigDict
+        // assignment and silently dropped), so mangle them like any other reserved word
+        reservedWords.addAll(GENERATED_MODEL_MEMBER_NAMES);
+        for (String memberName : PYDANTIC_BASE_MODEL_MEMBER_NAMES) {
+            if (memberName.startsWith("model_")) {
+                reservedWords.add(memberName);
+            }
+        }
+
         // clear import mapping (from default generator) as python does not use it
         // at the moment
         importMapping.clear();

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

@@ -1267,9 +1267,11 @@ public void testUnmappedMemberCollisionsRemainOutsideNameMappingValidation()
                 "src/test/resources/3_0/python/model-attribute-alias.yaml");
         final Path model = Paths.get(outputPath + "openapi_client/models/alias_model.py");
 
+        // unmapped collisions are not rejected; they fall back to reserved-word
+        // mangling and keep their wire name through the alias
         assertFileContains(model,
-                "    model_dump: Optional[StrictStr]",
-                "    to_dict: Optional[StrictStr]");
+                "    var_model_dump: Optional[StrictStr] = Field(default=None, alias=\"model_dump\")",
+                "    var_to_dict: Optional[StrictStr] = Field(default=None, alias=\"to_dict\")");
     }
 
     @Test
@@ -1358,6 +1360,22 @@ public void testModelNameMappingDoesNotRenameParameters() {
         Assert.assertEquals(codegen.toParamName("some-value"), "parameter_value");
     }
 
+    @Test
+    public void testGeneratedHelperAndPydanticNamesAreReserved() {
+        final PythonClientCodegen codegen = new PythonClientCodegen();
+
+        // names of the helper methods generated on every model
+        Assert.assertEquals(codegen.toVarName("to_dict"), "var_to_dict");
+        Assert.assertEquals(codegen.toVarName("from_dict"), "var_from_dict");
+        Assert.assertEquals(codegen.toVarName("to_json"), "var_to_json");
+        // pydantic BaseModel namespace
+        Assert.assertEquals(codegen.toVarName("model_config"), "var_model_config");
+        Assert.assertEquals(codegen.toVarName("model_fields"), "var_model_fields");
+        Assert.assertEquals(codegen.toVarName("model_dump"), "var_model_dump");
+        // similar-looking names must not be mangled
+        Assert.assertEquals(codegen.toVarName("model_configuration"), "model_configuration");
+    }
+
     @Test(dataProvider = "numberMappings")
     public void testMapNumberTo(String mapToNumber, String expectedType) throws IOException {
         File output = Files.createTempDirectory("test").toFile().getCanonicalFile();