[kotlin-client] preserve nullable list item types (#23655)

The kotlin-client mustache templates dropped `?` on nullable items
inside List/Array generics. With `items: { type: string, nullable: true }`,
properties now render as `List<kotlin.String?>` instead of
`List<kotlin.String>`, matching kotlin-spring server behavior.

Adds two regression sample configs (jvm-okhttp/moshi and multiplatform/
kotlinx-serialization) plus their generated samples.

Author: walterbrebels

.github/workflows/samples-kotlin-client.yaml

@@ -53,6 +53,8 @@ jobs:
           - samples/client/petstore/kotlin-enum-integers-multiplatform
           - samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4
           - samples/client/petstore/kotlin-array-simple-string-multiplatform
+          - samples/client/petstore/kotlin-array-nullable-items
+          - samples/client/petstore/kotlin-array-nullable-items-multiplatform
           - samples/client/petstore/kotlin-bigdecimal-default-multiplatform
           - samples/client/petstore/kotlin-bigdecimal-default-okhttp4
           - samples/client/petstore/kotlin-jvm-jackson

bin/configs/kotlin-array-nullable-items-multiplatform.yaml

@@ -0,0 +1,8 @@
+generatorName: kotlin
+outputDir: samples/client/petstore/kotlin-array-nullable-items-multiplatform
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/kotlin-array-nullable-items.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-client
+additionalProperties:
+  artifactId: kotlin-array-nullable-items-multiplatform
+  library: multiplatform
+  dateLibrary: kotlinx-datetime

bin/configs/kotlin-array-nullable-items.yaml

@@ -0,0 +1,6 @@
+generatorName: kotlin
+outputDir: samples/client/petstore/kotlin-array-nullable-items
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/kotlin-array-nullable-items.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-client
+additionalProperties:
+  artifactId: kotlin-array-nullable-items

modules/openapi-generator/src/main/resources/kotlin-client/data_class_opt_var.mustache

@@ -21,4 +21,4 @@
     {{#deprecated}}
     @Deprecated(message = "This property is deprecated.")
     {{/deprecated}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") {{/multiplatform}}{{#isInherited}}override {{/isInherited}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}? = {{^defaultValue}}null{{/defaultValue}}{{#defaultValue}}{{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{^multiplatform}}{{{dataType}}}("{{{defaultValue}}}"){{/multiplatform}}{{#multiplatform}}({{{defaultValue}}}).toDouble(){{/multiplatform}}{{/isNumber}}{{/defaultValue}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") {{/multiplatform}}{{#isInherited}}override {{/isInherited}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}{{#items.isNullable}}?{{/items.isNullable}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}? = {{^defaultValue}}null{{/defaultValue}}{{#defaultValue}}{{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{^multiplatform}}{{{dataType}}}("{{{defaultValue}}}"){{/multiplatform}}{{#multiplatform}}({{{defaultValue}}}).toDouble(){{/multiplatform}}{{/isNumber}}{{/defaultValue}}

modules/openapi-generator/src/main/resources/kotlin-client/data_class_req_var.mustache

@@ -21,4 +21,4 @@
     {{#deprecated}}
     @Deprecated(message = "This property is deprecated.")
     {{/deprecated}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required {{/multiplatform}}{{#isInherited}}override {{/isInherited}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}{{#defaultValue}} = {{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{^multiplatform}}{{{dataType}}}("{{{defaultValue}}}"){{/multiplatform}}{{#multiplatform}}({{{defaultValue}}}).toDouble(){{/multiplatform}}{{/isNumber}}{{/defaultValue}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required {{/multiplatform}}{{#isInherited}}override {{/isInherited}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}{{#items.isNullable}}?{{/items.isNullable}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}{{#defaultValue}} = {{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{^multiplatform}}{{{dataType}}}("{{{defaultValue}}}"){{/multiplatform}}{{#multiplatform}}({{{defaultValue}}}).toDouble(){{/multiplatform}}{{/isNumber}}{{/defaultValue}}

modules/openapi-generator/src/main/resources/kotlin-client/interface_opt_var.mustache

@@ -15,4 +15,4 @@
     {{^isEnum}}{{^isArray}}{{^isPrimitiveType}}{{^isModel}}@Contextual {{/isModel}}{{/isPrimitiveType}}{{/isArray}}{{/isEnum}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/kotlinx_serialization}}
     {{/multiplatform}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") abstract {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}?
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") abstract {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}{{#items.isNullable}}?{{/items.isNullable}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}?

modules/openapi-generator/src/main/resources/kotlin-client/interface_req_var.mustache

@@ -15,4 +15,4 @@
     {{^isEnum}}{{^isArray}}{{^isPrimitiveType}}{{^isModel}}@Contextual {{/isModel}}{{/isPrimitiveType}}{{/isArray}}{{/isEnum}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/kotlinx_serialization}}
     {{/multiplatform}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required abstract {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required abstract {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}{{#uniqueItems}}Set{{/uniqueItems}}{{^uniqueItems}}List{{/uniqueItems}}{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}{{#items.isNullable}}?{{/items.isNullable}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}

modules/openapi-generator/src/test/resources/3_0/kotlin/kotlin-array-nullable-items.yaml

@@ -0,0 +1,33 @@
+openapi: 3.0.0
+info:
+  title: 'Kotlin client — nullable array items'
+  description: Regression spec for nullable items inside list/array properties.
+  version: latest
+paths:
+  '/':
+    get:
+      operationId: getModel
+      responses:
+        '200':
+          description: Success
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ArrayWithNullableItemsModel'
+components:
+  schemas:
+    ArrayWithNullableItemsModel:
+      type: object
+      required:
+        - requiredItems
+      properties:
+        requiredItems:
+          type: array
+          items:
+            type: string
+            nullable: true
+        optionalItems:
+          type: array
+          items:
+            type: string
+            nullable: true

samples/client/petstore/kotlin-array-nullable-items-multiplatform/.openapi-generator-ignore

@@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md

samples/client/petstore/kotlin-array-nullable-items-multiplatform/.openapi-generator/FILES

@@ -0,0 +1,24 @@
+README.md
+build.gradle.kts
+docs/ArrayWithNullableItemsModel.md
+docs/DefaultApi.md
+gradle/wrapper/gradle-wrapper.jar
+gradle/wrapper/gradle-wrapper.properties
+gradlew
+gradlew.bat
+settings.gradle.kts
+src/commonMain/kotlin/org/openapitools/client/apis/DefaultApi.kt
+src/commonMain/kotlin/org/openapitools/client/auth/ApiKeyAuth.kt
+src/commonMain/kotlin/org/openapitools/client/auth/Authentication.kt
+src/commonMain/kotlin/org/openapitools/client/auth/HttpBasicAuth.kt
+src/commonMain/kotlin/org/openapitools/client/auth/HttpBearerAuth.kt
+src/commonMain/kotlin/org/openapitools/client/auth/OAuth.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiAbstractions.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/Base64ByteArray.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/HttpResponse.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/OctetByteArray.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/PartConfig.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
+src/commonMain/kotlin/org/openapitools/client/infrastructure/RequestMethod.kt
+src/commonMain/kotlin/org/openapitools/client/models/ArrayWithNullableItemsModel.kt