[Kotlin][client] Add nullable query parameter support (#4197)

* add nullable query parameter support

* remove redundant bracket

Author: wing328

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

@@ -1893,7 +1893,7 @@ public CodegenModel fromModel(String name, Schema schema) {
                 }
             }
 
-            if(composed.getRequired() != null) {
+            if (composed.getRequired() != null) {
                 required.addAll(composed.getRequired());
             }
             addVars(m, unaliasPropertySchema(properties), required, unaliasPropertySchema(allProperties), allRequired);
@@ -2002,7 +2002,7 @@ protected void addProperties(Map<String, Schema> properties, List<String> requir
                 addProperties(properties, required, component);
             }
 
-            if(schema.getRequired() != null) {
+            if (schema.getRequired() != null) {
                 required.addAll(schema.getRequired());
             }
 
@@ -2508,15 +2508,15 @@ protected ApiResponse findMethodResponse(ApiResponses responses) {
     /**
      * Set op's returnBaseType, returnType, examples etc.
      *
-     * @param operation endpoint Operation
-     * @param schemas a map of the schemas in the openapi spec
-     * @param op endpoint CodegenOperation
+     * @param operation      endpoint Operation
+     * @param schemas        a map of the schemas in the openapi spec
+     * @param op             endpoint CodegenOperation
      * @param methodResponse the default ApiResponse for the endpoint
      */
     protected void handleMethodResponse(Operation operation,
-                                     Map<String, Schema> schemas,
-                                     CodegenOperation op,
-                                     ApiResponse methodResponse) {
+                                        Map<String, Schema> schemas,
+                                        CodegenOperation op,
+                                        ApiResponse methodResponse) {
         Schema responseSchema = ModelUtils.unaliasSchema(this.openAPI, ModelUtils.getSchemaFromResponse(methodResponse));
 
         if (responseSchema != null) {
@@ -4101,7 +4101,7 @@ public String sanitizeName(String name, String removeCharRegEx) {
      *
      * @param name            string to be sanitize
      * @param removeCharRegEx a regex containing all char that will be removed
-     * @param exceptionList a list of matches which should not be sanitized (i.e expections)
+     * @param exceptionList   a list of matches which should not be sanitized (i.e expections)
      * @return sanitized string
      */
     @SuppressWarnings("static-method")
@@ -4529,8 +4529,8 @@ public boolean hasFormParameter(OpenAPI openAPI, Operation operation) {
 
         for (String consume : consumesInfo) {
             if (consume != null &&
-                (consume.toLowerCase(Locale.ROOT).startsWith("application/x-www-form-urlencoded") ||
-                consume.toLowerCase(Locale.ROOT).startsWith("multipart"))) {
+                    (consume.toLowerCase(Locale.ROOT).startsWith("application/x-www-form-urlencoded") ||
+                            consume.toLowerCase(Locale.ROOT).startsWith("multipart"))) {
                 return true;
             }
         }
@@ -5022,7 +5022,6 @@ public CodegenParameter fromRequestBody(RequestBody body, Set<String> imports, S
                 codegenParameter.pattern = codegenProperty.pattern;
 
 
-
                 if (codegenProperty.complexType != null) {
                     imports.add(codegenProperty.complexType);
                 }

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

@@ -33,9 +33,21 @@ import {{packageName}}.infrastructure.toMultiValue
 {{/hasQueryParams}}{{#hasQueryParams}}mutableMapOf<kotlin.String, List<kotlin.String>>()
             .apply {
                 {{#queryParams}}
-                {{^required}}if ({{paramName}} != null) {
+                {{^required}}
+                if ({{paramName}} != null) {
                     put("{{paramName}}", {{#isContainer}}toMultiValue({{paramName}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{paramName}}.toString()){{/isContainer}})
-                }{{/required}}{{#required}}put("{{paramName}}", {{#isContainer}}toMultiValue({{paramName}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{paramName}}.toString()){{/isContainer}}){{/required}}
+                }
+                {{/required}}
+                {{#required}}
+                {{#isNullable}}
+                if ({{paramName}} != null) {
+                    put("{{paramName}}", {{#isContainer}}toMultiValue({{paramName}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{paramName}}.toString()){{/isContainer}})
+                }
+                {{/isNullable}}
+                {{^isNullable}}
+                put("{{paramName}}", {{#isContainer}}toMultiValue({{paramName}}.toList(), "{{collectionFormat}}"){{/isContainer}}{{^isContainer}}listOf({{paramName}}.toString()){{/isContainer}})
+                {{/isNullable}}
+                {{/required}}
                 {{/queryParams}}
             }
             {{/hasQueryParams}}