From 0b652fe1d2e00aef9d0cf2ff9f841b3ae3418005 Mon Sep 17 00:00:00 2001
From: Yan Zhu <hackzhuyan@gmail.com>
Date: Tue, 21 Jul 2026 12:26:26 +0800
Subject: [PATCH] fix(go-server): avoid AssertstringRequired for
 primitive-typed models

oneOf/nullable enums can flatten to *string while still flagged as models,
so templates must not emit Assertstring* helpers that do not exist.

Signed-off-by: Yan Zhu <hackzhuyan@gmail.com>
---
 .../codegen/languages/GoServerCodegen.java    | 42 +++++++++++++++++++
 .../main/resources/go-server/model.mustache   |  8 ++++
 .../codegen/goserver/GoServerCodegenTest.java | 19 +++++++++
 .../3_0/go-server/assert-primitive-model.yaml | 35 ++++++++++++++++
 4 files changed, 104 insertions(+)
 create mode 100644 modules/openapi-generator/src/test/resources/3_0/go-server/assert-primitive-model.yaml

diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoServerCodegen.java
index 9356bb7347f2..6e45e37ade46 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoServerCodegen.java
@@ -341,6 +341,12 @@ private void configureModelRequiredValidation(CodegenModel model, List<Map<Strin
             decodeVarsByBaseName.put(v.baseName, v);
         }
         List<CodegenProperty> decodeVars = new ArrayList<>(decodeVarsByBaseName.values());
+        for (CodegenProperty v : decodeVars) {
+            clearModelFlagForPrimitives(v);
+        }
+        for (CodegenProperty v : model.vars) {
+            clearModelFlagForPrimitives(v);
+        }
         model.vendorExtensions.put("decodeVars", decodeVars);
 
         List<CodegenProperty> presenceCheckRequiredVars = decodeVars.stream()
@@ -377,6 +383,42 @@ private void configureModelRequiredValidation(CodegenModel model, List<Map<Strin
         }
     }
 
+    /**
+     * oneOf/anyOf nullable enums often end up as Go {@code *string} while still marked
+     * {@code isModel=true}, which makes go-server templates emit non-existent Assertstring* helpers.
+     */
+    private void clearModelFlagForPrimitives(CodegenProperty property) {
+        if (property == null) {
+            return;
+        }
+        if (isGoPrimitiveProperty(property)) {
+            property.isModel = false;
+            property.isPrimitiveType = true;
+        }
+        clearModelFlagForPrimitives(property.items);
+        clearModelFlagForPrimitives(property.mostInnerItems);
+    }
+
+    private boolean isGoPrimitiveProperty(CodegenProperty property) {
+        if (property.isPrimitiveType || property.isString || property.isNumber || property.isInteger
+                || property.isLong || property.isBoolean || property.isFloat || property.isDouble
+                || property.isByteArray || property.isBinary || property.isFile
+                || property.isDate || property.isDateTime || property.isUuid) {
+            return true;
+        }
+        if (languageSpecificPrimitives().contains(property.baseType)) {
+            return true;
+        }
+        String dataType = property.dataType;
+        if (dataType == null) {
+            return false;
+        }
+        if (dataType.startsWith("*")) {
+            dataType = dataType.substring(1);
+        }
+        return languageSpecificPrimitives().contains(dataType);
+    }
+
     @Override
     public ModelsMap postProcessModels(ModelsMap objs) {
         // The superclass determines the list of required golang imports. The actual list of imports
diff --git a/modules/openapi-generator/src/main/resources/go-server/model.mustache b/modules/openapi-generator/src/main/resources/go-server/model.mustache
index 4a38893652f2..68c903449021 100644
--- a/modules/openapi-generator/src/main/resources/go-server/model.mustache
+++ b/modules/openapi-generator/src/main/resources/go-server/model.mustache
@@ -117,17 +117,21 @@ func Assert{{classname}}Required(obj {{classname}}) error {
 		{{/isArray}}
 	{{/isNullable}}
 	{{#isModel}}
+	{{^isPrimitiveType}}
 {{#isNullable}}	{{/isNullable}}	if err := Assert{{baseType}}Required({{#isNullable}}*{{/isNullable}}obj.{{name}}); err != nil {
 {{#isNullable}}	{{/isNullable}}		return err
 {{#isNullable}}	{{/isNullable}}	}
+	{{/isPrimitiveType}}
 	{{/isModel}}
 	{{#isArray}}
 		{{#items.isModel}}
+		{{^items.isPrimitiveType}}
 {{#isNullable}}	{{/isNullable}}	for _, el := range {{#isNullable}}*{{/isNullable}}obj.{{name}} {
 {{#isNullable}}	{{/isNullable}}		if err := Assert{{items.baseType}}Required(el); err != nil {
 {{#isNullable}}	{{/isNullable}}			return err
 {{#isNullable}}	{{/isNullable}}		}
 {{#isNullable}}	{{/isNullable}}	}
+		{{/items.isPrimitiveType}}
 		{{/items.isModel}}
 		{{^items.isModel}}
 			{{#mostInnerItems.isModel}}
@@ -186,17 +190,21 @@ func Assert{{classname}}Constraints(obj {{classname}}) error {
 {{/isArray}}
 {{/isNullable}}
 {{#isModel}}
+{{^isPrimitiveType}}
 {{#isNullable}}     {{/isNullable}}	if err := Assert{{baseType}}Constraints({{#isNullable}}*{{/isNullable}}obj.{{name}}); err != nil {
 {{#isNullable}}     {{/isNullable}}		return err
 {{#isNullable}}     {{/isNullable}}	}
+{{/isPrimitiveType}}
 {{/isModel}}
 {{#isArray}}
 {{#items.isModel}}
+{{^items.isPrimitiveType}}
 {{#isNullable}}     {{/isNullable}}	for _, el := range {{#isNullable}}*{{/isNullable}}obj.{{name}} {
 {{#isNullable}}     {{/isNullable}}		if err := Assert{{items.baseType}}Constraints(el); err != nil {
 {{#isNullable}}     {{/isNullable}}			return err
 {{#isNullable}}     {{/isNullable}}		}
 {{#isNullable}}     {{/isNullable}}	}
+{{/items.isPrimitiveType}}
 {{/items.isModel}}
 {{^items.isModel}}
 {{#mostInnerItems.isModel}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/goserver/GoServerCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/goserver/GoServerCodegenTest.java
index a773d05b3364..6cdcd549df3d 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/goserver/GoServerCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/goserver/GoServerCodegenTest.java
@@ -272,4 +272,23 @@ public void verifyReadOnlyRequiredFieldsNotEnforced() throws IOException {
                 "if err := AssertMetaRequired(obj.Meta); err != nil {");
     }
 
+    @Test
+    public void verifyNoAssertstringRequiredForPrimitiveTypedModels() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = createDefaultCodegenConfigurator(output)
+                .setInputSpec("src/test/resources/3_0/go-server/assert-primitive-model.yaml");
+
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(configurator.toClientOptInput()).generate();
+        files.forEach(File::deleteOnExit);
+
+        java.nio.file.Path modelPath = Paths.get(output + "/go/model_thing.go");
+        TestUtils.assertFileExists(modelPath);
+        TestUtils.assertFileNotContains(modelPath, "AssertstringRequired");
+        TestUtils.assertFileNotContains(modelPath, "AssertstringConstraints");
+        TestUtils.assertFileContains(modelPath, "func AssertThingRequired(obj Thing) error {\n\treturn nil");
+    }
+
 }
diff --git a/modules/openapi-generator/src/test/resources/3_0/go-server/assert-primitive-model.yaml b/modules/openapi-generator/src/test/resources/3_0/go-server/assert-primitive-model.yaml
new file mode 100644
index 000000000000..cf233c2e2944
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/go-server/assert-primitive-model.yaml
@@ -0,0 +1,35 @@
+openapi: 3.0.1
+info:
+  version: 1.0.0
+  title: composed nullable enum must not emit primitive Assert helpers
+paths:
+  /thing:
+    post:
+      operationId: createThing
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/Thing'
+      responses:
+        '201':
+          description: created
+components:
+  schemas:
+    Mode:
+      type: string
+      enum: [On, Off]
+    Thing:
+      type: object
+      properties:
+        mode:
+          nullable: true
+          oneOf:
+            - $ref: '#/components/schemas/Mode'
+            - enum: [null]
+        tags:
+          type: array
+          items:
+            $ref: '#/components/schemas/Mode'
+            nullable: true