fix(go-server): skip readOnly fields in AssertXxxRequired

modules/openapi-generator/src/main/resources/go-server/model.mustache

@@ -80,8 +80,8 @@ type {{classname}} struct {
 func Assert{{classname}}Required(obj {{classname}}) error {
 {{#hasRequired}}
 	elements := map[string]interface{}{
-{{#requiredVars}}		"{{baseName}}": obj.{{name}},
-{{/requiredVars}}	}
+{{#requiredVars}}{{^isReadOnly}}		"{{baseName}}": obj.{{name}},
+{{/isReadOnly}}{{/requiredVars}}	}
 	for name, el := range elements {
 		if isZero := IsZeroValue(el); isZero {
 			return &RequiredError{Field: name}
@@ -100,6 +100,7 @@ func Assert{{classname}}Required(obj {{classname}}) error {
 	{{/isMap}}
 {{/parent}}
 {{#Vars}}
+{{^isReadOnly}}
 	{{#isNullable}}
 		{{#isModel}}
 	if obj.{{name}} != nil {
@@ -157,13 +158,15 @@ func Assert{{classname}}Required(obj {{classname}}) error {
 			{{/items.isModel}}
 		{{/isArray}}
 	{{/isNullable}}
+{{/isReadOnly}}
 {{/Vars}}
 	return nil
 }
 
 // Assert{{classname}}Constraints checks if the values respects the defined constraints
 func Assert{{classname}}Constraints(obj {{classname}}) error {
 {{#Vars}}
+{{^isReadOnly}}
 {{#minimum}}
 	if {{#isNullable}}obj.{{name}} != nil && *{{/isNullable}}obj.{{name}} < {{minimum}} {
 		return &ParsingError{Param: "{{name}}", Err: errors.New(errMsgMinValueConstraint)}
@@ -229,6 +232,7 @@ func Assert{{classname}}Constraints(obj {{classname}}) error {
 {{/items.isModel}}
 {{/isArray}}
 {{/isNullable}}
+{{/isReadOnly}}
 {{/Vars}}
 	return nil
 }{{/model}}{{/models}}

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

@@ -74,6 +74,37 @@ public void verifyOrder() throws IOException {
 
     }
 
+    @Test
+    public void verifyReadOnlyRequiredFieldsNotEnforced() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = createDefaultCodegenConfigurator(output)
+                .setInputSpec("src/test/resources/3_0/go-server/readonly-required.yaml");
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        // AssertThingRequired must not reference the readOnly "id" field, so a
+        // request body that legitimately omits it is accepted. The non-readOnly
+        // required "name" field must still be enforced.
+        java.nio.file.Path modelPath = Paths.get(output + "/go/model_thing.go");
+        TestUtils.assertFileExists(modelPath);
+        TestUtils.assertFileContains(modelPath,
+                "func AssertThingRequired(obj Thing) error {");
+        TestUtils.assertFileContains(modelPath,
+                "\"name\": obj.Name,");
+        // readOnly "id" must be skipped
+        TestUtils.assertFileNotContains(modelPath,
+                "\"id\": obj.Id,");
+        // readOnly nested model "meta" must not be recursed into, so a
+        // request body that omits it (and thus omits Meta's own required
+        // fields) is accepted.
+        TestUtils.assertFileNotContains(modelPath,
+                "if err := AssertMetaRequired(obj.Meta); err != nil {");
+    }
+
     private static CodegenConfigurator createDefaultCodegenConfigurator(File output) {
         return new CodegenConfigurator()
                 .setGeneratorName("go-server")

modules/openapi-generator/src/test/resources/3_0/go-server/readonly-required.yaml

@@ -0,0 +1,45 @@
+openapi: 3.0.1
+
+info:
+  version: 1.0.0
+  title: readOnly required fields must not be enforced on request bodies
+
+paths:
+  /thing:
+    post:
+      operationId: createThing
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/Thing'
+      responses:
+        '201':
+          description: created
+
+components:
+  schemas:
+    Thing:
+      type: object
+      properties:
+        id:
+          type: string
+          readOnly: true
+        name:
+          type: string
+        meta:
+          readOnly: true
+          allOf:
+            - $ref: '#/components/schemas/Meta'
+      required:
+        - id
+        - name
+        - meta
+    Meta:
+      type: object
+      properties:
+        createdBy:
+          type: string
+      required:
+        - createdBy