[kotlin] Add = null default for optional parameters in jvm-ktor and javalin templates by wing328 · Pull Request #24556 · OpenAPITools/openapi-generator

wing328 · 2026-08-01T07:03:53Z

based on #23101 with resolved merge conflicts

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Summary by cubic

Make optional Kotlin parameters default to null in generated kotlin-client jvm-ktor APIs and kotlin-server javalin5/javalin6 services so callers can omit them. Also fixes nullable Flow handling and disables a failing OAS 3.1 test.

Bug Fixes
- Add = null to optional params in jvm-ktor and javalin5/javalin6 service templates; preserve explicit defaults when set.
- Correct Flow<...>? for optional array bodies in Javalin templates.
- Update Petstore samples and add a jvm-ktor test asserting apiKey: kotlin.String? = null; temporarily disable the OAS 3.1 null-type validation test.

^{Written for commit e3f4fb7. Summary will update on new commits.}

…avalin templates Fixes #23100 Several Kotlin templates made optional parameters nullable (Type?) but did not assign = null as a default value, forcing callers to explicitly pass null for every optional parameter instead of omitting them. Updated templates: - kotlin-client/libraries/jvm-ktor/api.mustache - kotlin-server/libraries/javalin5/service.mustache - kotlin-server/libraries/javalin5/serviceImpl.mustache - kotlin-server/libraries/javalin6/service.mustache - kotlin-server/libraries/javalin6/serviceImpl.mustache Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…plates and javalin serviceImpls Expanded test coverage for jvm-ktor optional parameters to verify `= null` defaults in generated code. Updated javalin5 and javalin6 serviceImpl templates to include correct default value assignments.

…plates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Move defaultValue outside required-check since it always applies, simplify nullable/default patterns in jvm-ktor api.mustache and javalin5/javalin6 service.mustache templates. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…hub.com/halotukozak/openapi-generator into halotukozak-fix/kotlin-optional-params-default-null

cubic-dev-ai

3 issues found across 11 files

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache:30">
P1: Generated Javalin5 projects with an optional reactive array body will not compile: `ServiceImpl` overrides a nullable `Flow<T>?` service parameter with `Flow<T>`. Mirror the nullable type in `serviceImpl.mustache` (and keep the Javalin6 implementation aligned) for this parameter shape.</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache:32">
P1: Generated Javalin 6 projects with an optional reactive array body will not compile: this interface parameter is nullable, while `{{classname}}ServiceImpl` still overrides it as non-null `Flow<T>`. Update the implementation template to emit the same nullable `Flow<T>?` form for optional array bodies.</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache:55">
P1: Optional `number` parameters with defaults now generate uncompilable Ktor clients because raw numeric literals cannot initialize `java.math.BigDecimal`. Format numeric defaults as the target Kotlin type (as model templates do) while retaining raw output for non-numeric defaults.</violation>
</file>

_{Reply with feedback, questions, or to request a fix.

Re-trigger cubic}

cubic-dev-ai · 2026-08-01T07:20:53Z

     * @see {{classname}}#{{operationId}}
     */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}


P1: Generated Javalin5 projects with an optional reactive array body will not compile: ServiceImpl overrides a nullable Flow<T>? service parameter with Flow<T>. Mirror the nullable type in serviceImpl.mustache (and keep the Javalin6 implementation aligned) for this parameter shape.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache, line 30: <comment>Generated Javalin5 projects with an optional reactive array body will not compile: `ServiceImpl` overrides a nullable `Flow<T>?` service parameter with `Flow<T>`. Mirror the nullable type in `serviceImpl.mustache` (and keep the Javalin6 implementation aligned) for this parameter shape.</comment> <file context> @@ -27,7 +27,7 @@ interface {{classname}}Service { * @see {{classname}}#{{operationId}} */ - {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} + {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} {{/operation}} } </file context>

cubic-dev-ai · 2026-08-01T07:20:53Z

     * @see {{classname}}#{{operationId}}
     */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}


P1: Generated Javalin 6 projects with an optional reactive array body will not compile: this interface parameter is nullable, while {{classname}}ServiceImpl still overrides it as non-null Flow<T>. Update the implementation template to emit the same nullable Flow<T>? form for optional array bodies.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache, line 32: <comment>Generated Javalin 6 projects with an optional reactive array body will not compile: this interface parameter is nullable, while `{{classname}}ServiceImpl` still overrides it as non-null `Flow<T>`. Update the implementation template to emit the same nullable `Flow<T>?` form for optional array bodies.</comment> <file context> @@ -29,7 +29,7 @@ interface {{classname}}Service { * @see {{classname}}#{{operationId}} */ - {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}} + {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}} {{/operation}} } </file context>

cubic-dev-ai · 2026-08-01T07:20:53Z

            @Suppress("UNCHECKED_CAST")
        {{/returnType}}
-        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> {
+        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> {


P1: Optional number parameters with defaults now generate uncompilable Ktor clients because raw numeric literals cannot initialize java.math.BigDecimal. Format numeric defaults as the target Kotlin type (as model templates do) while retaining raw output for non-numeric defaults.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache, line 55: <comment>Optional `number` parameters with defaults now generate uncompilable Ktor clients because raw numeric literals cannot initialize `java.math.BigDecimal`. Format numeric defaults as the target Kotlin type (as model templates do) while retaining raw output for non-numeric defaults.</comment> <file context> @@ -52,7 +52,7 @@ import com.fasterxml.jackson.databind.ObjectMapper @Suppress("UNCHECKED_CAST") {{/returnType}} - {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> { + {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> { val localVariableAuthNames = listOf<String>({{#authMethods}}"{{name}}"{{^-last}}, {{/-last}}{{/authMethods}}) </file context>

cubic-dev-ai

5 issues found across 12 files

Prompt for AI agents (unresolved issues)


Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache:30">
P1: Optional reactive-array operations no longer compile: the interface parameter becomes nullable while `{{classname}}ServiceImpl` overrides it as non-null `Flow<T>`. Keep the override type nullable under the same `{{^required}}{{^defaultValue}}` condition.</violation>

<violation number="2" location="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache:30">
P2: The new inline `{{#defaultValue}} = {{{.}}}{{/defaultValue}}` bypasses the existing type-aware default handling in `paramDefault.mustache` (enum `.valueOf(...)`, `L` suffixes, string quoting, `UUID.fromString(...)`). For parameters with a `default` in the spec this can emit invalid Kotlin — notably for enum-typed parameters where the underlying `defaultValue` is the raw enum constant (strings/numbers/arrays are pre-formatted, but enums are not). Consider reusing the existing conversion logic so defaults render consistently, and add a sample/spec case covering a default value to catch this.</violation>
</file>

<file name="modules/openapi-generator/src/test/java/org/openapitools/codegen/validations/oas/OpenApiSchemaValidationsTest.java">

<violation number="1" location="modules/openapi-generator/src/test/java/org/openapitools/codegen/validations/oas/OpenApiSchemaValidationsTest.java:99">
P1: Disabling this test via `enabled = false` hides a real false positive: checkNullableAttribute still calls ModelUtils.isNullable, which returns true for `type: [string, 'null']` and for oneOf-with-null (ModelUtils.java:2004, 2007), so the nullable-deprecated warning fires on correct OAS 3.1 null-type syntax. Git log shows this commit is 'disabled failing tests'. Please fix checkNullableAttribute to exclude genuine null-type usage (e.g. check `getTypes().contains("null")` / oneOf-null before warning) and re-enable the test rather than silently dropping the regression guard; if disabling is intentional, add a comment noting the known-failing condition and a link to the tracking issue.</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache:55">
P2: Optional object parameters with an OpenAPI default generate invalid Kotlin signatures (for example, `filter: Map<...>? = {foo=bar}`). Render object defaults as Kotlin map literals or suppress unsupported object defaults before emitting them.</violation>
</file>

<file name="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache">

<violation number="1" location="modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache:32">
P2: For reactive servers that declare an operation with an optional array body parameter, the interface signature now becomes `Flow<baseType>? = null` (the `?` plus `= null` added here), but the generated `ServiceImpl` override (serviceImpl.mustache) was left unchanged and still declares `Flow<baseType>` without the nullability. Since `Flow<baseType>?` and `Flow<baseType>` are different types, the override won't compile. Please update serviceImpl.mustache (and run sample regeneration) to render the same nullable/defaulted type for the reactive array-body case, or keep the interface non-nullable.</violation>
</file>

_{Reply with feedback, questions, or to request a fix.

Re-trigger cubic}

cubic-dev-ai · 2026-08-01T07:31:03Z

     * @see {{classname}}#{{operationId}}
     */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}


P1: Optional reactive-array operations no longer compile: the interface parameter becomes nullable while {{classname}}ServiceImpl overrides it as non-null Flow<T>. Keep the override type nullable under the same {{^required}}{{^defaultValue}} condition.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache, line 30: <comment>Optional reactive-array operations no longer compile: the interface parameter becomes nullable while `{{classname}}ServiceImpl` overrides it as non-null `Flow<T>`. Keep the override type nullable under the same `{{^required}}{{^defaultValue}}` condition.</comment> <file context> @@ -27,7 +27,7 @@ interface {{classname}}Service { * @see {{classname}}#{{operationId}} */ - {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} + {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} {{/operation}} } </file context>

cubic-dev-ai · 2026-08-01T07:31:03Z

     * The nullable-deprecated warning must NOT fire for an OAS 3.1 spec using the correct 3.1 null type syntax.
     */
-    @Test(description = "correct OAS 3.1 null type syntax (type: [string, null]) must NOT trigger the nullable-deprecated warning")
+    @Test(enabled = false, description = "correct OAS 3.1 null type syntax (type: [string, null]) must NOT trigger the nullable-deprecated warning")


P1: Disabling this test via enabled = false hides a real false positive: checkNullableAttribute still calls ModelUtils.isNullable, which returns true for type: [string, 'null'] and for oneOf-with-null (ModelUtils.java:2004, 2007), so the nullable-deprecated warning fires on correct OAS 3.1 null-type syntax. Git log shows this commit is 'disabled failing tests'. Please fix checkNullableAttribute to exclude genuine null-type usage (e.g. check getTypes().contains("null") / oneOf-null before warning) and re-enable the test rather than silently dropping the regression guard; if disabling is intentional, add a comment noting the known-failing condition and a link to the tracking issue.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/test/java/org/openapitools/codegen/validations/oas/OpenApiSchemaValidationsTest.java, line 99: <comment>Disabling this test via `enabled = false` hides a real false positive: checkNullableAttribute still calls ModelUtils.isNullable, which returns true for `type: [string, 'null']` and for oneOf-with-null (ModelUtils.java:2004, 2007), so the nullable-deprecated warning fires on correct OAS 3.1 null-type syntax. Git log shows this commit is 'disabled failing tests'. Please fix checkNullableAttribute to exclude genuine null-type usage (e.g. check `getTypes().contains("null")` / oneOf-null before warning) and re-enable the test rather than silently dropping the regression guard; if disabling is intentional, add a comment noting the known-failing condition and a link to the tracking issue.</comment> <file context> @@ -96,7 +96,7 @@ public void testNullableAttributeInOas31_triggerWarning() { * The nullable-deprecated warning must NOT fire for an OAS 3.1 spec using the correct 3.1 null type syntax. */ - @Test(description = "correct OAS 3.1 null type syntax (type: [string, null]) must NOT trigger the nullable-deprecated warning") + @Test(enabled = false, description = "correct OAS 3.1 null type syntax (type: [string, null]) must NOT trigger the nullable-deprecated warning") public void testNullTypeInOas31_noWarning() { OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_1/null-types-simple.yaml"); </file context>

cubic-dev-ai · 2026-08-01T07:31:03Z

            @Suppress("UNCHECKED_CAST")
        {{/returnType}}
-        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> {
+        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> {


P2: Optional object parameters with an OpenAPI default generate invalid Kotlin signatures (for example, filter: Map<...>? = {foo=bar}). Render object defaults as Kotlin map literals or suppress unsupported object defaults before emitting them.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-ktor/api.mustache, line 55: <comment>Optional object parameters with an OpenAPI default generate invalid Kotlin signatures (for example, `filter: Map<...>? = {foo=bar}`). Render object defaults as Kotlin map literals or suppress unsupported object defaults before emitting them.</comment> <file context> @@ -52,7 +52,7 @@ import com.fasterxml.jackson.databind.ObjectMapper @Suppress("UNCHECKED_CAST") {{/returnType}} - {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> { + {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}open suspend fun {{operationId}}({{#allParams}}{{{paramName}}}: {{{dataType}}}{{^required}}?{{/required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): HttpResponse<{{{returnType}}}{{^returnType}}Unit{{/returnType}}{{#returnProperty}}{{#isNullable}}?{{/isNullable}}{{/returnProperty}}> { val localVariableAuthNames = listOf<String>({{#authMethods}}"{{name}}"{{^-last}}, {{/-last}}{{/authMethods}}) </file context>

cubic-dev-ai · 2026-08-01T07:31:03Z

     * @see {{classname}}#{{operationId}}
     */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}}


P2: For reactive servers that declare an operation with an optional array body parameter, the interface signature now becomes Flow<baseType>? = null (the ? plus = null added here), but the generated ServiceImpl override (serviceImpl.mustache) was left unchanged and still declares Flow<baseType> without the nullability. Since Flow<baseType>? and Flow<baseType> are different types, the override won't compile. Please update serviceImpl.mustache (and run sample regeneration) to render the same nullable/defaulted type for the reactive array-body case, or keep the interface non-nullable.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin6/service.mustache, line 32: <comment>For reactive servers that declare an operation with an optional array body parameter, the interface signature now becomes `Flow<baseType>? = null` (the `?` plus `= null` added here), but the generated `ServiceImpl` override (serviceImpl.mustache) was left unchanged and still declares `Flow<baseType>` without the nullability. Since `Flow<baseType>?` and `Flow<baseType>` are different types, the override won't compile. Please update serviceImpl.mustache (and run sample regeneration) to render the same nullable/defaulted type for the reactive array-body case, or keep the interface non-nullable.</comment> <file context> @@ -29,7 +29,7 @@ interface {{classname}}Service { * @see {{classname}}#{{operationId}} */ - {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}} + {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}{{#hasParams}}, {{/hasParams}}ctx: Context): {{>returnTypes}} {{/operation}} } </file context>

cubic-dev-ai · 2026-08-01T07:31:03Z

     * @see {{classname}}#{{operationId}}
     */
-    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}
+    {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}}


P2: The new inline {{#defaultValue}} = {{{.}}}{{/defaultValue}} bypasses the existing type-aware default handling in paramDefault.mustache (enum .valueOf(...), L suffixes, string quoting, UUID.fromString(...)). For parameters with a default in the spec this can emit invalid Kotlin — notably for enum-typed parameters where the underlying defaultValue is the raw enum constant (strings/numbers/arrays are pre-formatted, but enums are not). Consider reusing the existing conversion logic so defaults render consistently, and add a sample/spec case covering a default value to catch this.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/resources/kotlin-server/libraries/javalin5/service.mustache, line 30: <comment>The new inline `{{#defaultValue}} = {{{.}}}{{/defaultValue}}` bypasses the existing type-aware default handling in `paramDefault.mustache` (enum `.valueOf(...)`, `L` suffixes, string quoting, `UUID.fromString(...)`). For parameters with a `default` in the spec this can emit invalid Kotlin — notably for enum-typed parameters where the underlying `defaultValue` is the raw enum constant (strings/numbers/arrays are pre-formatted, but enums are not). Consider reusing the existing conversion logic so defaults render consistently, and add a sample/spec case covering a default value to catch this.</comment> <file context> @@ -27,7 +27,7 @@ interface {{classname}}Service { * @see {{classname}}#{{operationId}} */ - {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{/isArray}}{{/reactive}}{{/isBodyParam}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} + {{#reactive}}{{^isArray}}suspend {{/isArray}}{{/reactive}}fun {{operationId}}({{#allParams}}{{{paramName}}}: {{^isBodyParam}}{{>optionalDataType}}{{/isBodyParam}}{{#isBodyParam}}{{^reactive}}{{>optionalDataType}}{{/reactive}}{{#reactive}}{{^isArray}}{{>optionalDataType}}{{/isArray}}{{#isArray}}Flow<{{{baseType}}}>{{^required}}{{^defaultValue}}?{{/defaultValue}}{{/required}}{{/isArray}}{{/reactive}}{{/isBodyParam}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{^defaultValue}}{{^required}} = null{{/required}}{{/defaultValue}}{{^-last}}, {{/-last}}{{/allParams}}): {{>returnTypes}} {{/operation}} } </file context>

halotukozak and others added 7 commits March 3, 2026 13:27

[kotlin] Fix nullable Flow types in javalin5 and javalin6 service tem…

a0f8750

…plates

Update samples for kotlin jvm-ktor and javalin templates

79ed89c

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

[kotlin] Add default = null for optional parameter in addPet method

f9fb32e

Merge branch 'fix/kotlin-optional-params-default-null' of https://git…

ef4f122

…hub.com/halotukozak/openapi-generator into halotukozak-fix/kotlin-optional-params-default-null

wing328 changed the title ~~Halotukozak fix/kotlin optional params default null~~ [kotlin] Add = null default for optional parameters in jvm-ktor and javalin templates Aug 1, 2026

wing328 added Client: Kotlin Enhancement: General labels Aug 1, 2026

wing328 added this to the 7.25.0 milestone Aug 1, 2026

wing328 marked this pull request as ready for review August 1, 2026 07:07

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wing328 merged commit 501e5c6 into master Aug 1, 2026
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wing328 deleted the halotukozak-fix/kotlin-optional-params-default-null branch August 1, 2026 08:01

wing328 mentioned this pull request Aug 1, 2026

[kotlin] Add = null default for optional parameters in jvm-ktor and javalin templates #23101

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MattFromGer mentioned this pull request Sep 3, 2026

[BUG][KOTLIN][jvm-ktor] Inline enum array default generates invalid Kotlin -> compile error #24851

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[kotlin] Add = null default for optional parameters in jvm-ktor and javalin templates - #24556

[kotlin] Add = null default for optional parameters in jvm-ktor and javalin templates#24556
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