Fixes Kotlin client property names that include a dollar sign (#4229)

Property names that include a dollar sign are being interpreted
by Kotlin as a string template. This fix escapes such instances.

https://github.com/OpenAPITools/openapi-generator/issues/4228

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

@@ -19,7 +19,9 @@ package org.openapitools.codegen.languages;
 
 import org.openapitools.codegen.CliOption;
 import org.openapitools.codegen.CodegenConstants;
+import org.openapitools.codegen.CodegenModel;
 import org.openapitools.codegen.CodegenOperation;
+import org.openapitools.codegen.CodegenProperty;
 import org.openapitools.codegen.CodegenType;
 import org.openapitools.codegen.SupportingFile;
 
@@ -38,6 +40,8 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
     public static final String DATE_LIBRARY = "dateLibrary";
     public static final String COLLECTION_TYPE = "collectionType";
 
+    protected static final String VENDOR_EXTENSION_BASE_NAME_LITERAL = "x-base-name-literal";
+
     protected String dateLibrary = DateLibrary.JAVA8.value;
     protected String collectionType = CollectionType.ARRAY.value;
 
@@ -253,6 +257,31 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
         return getLibrary() != null && (getLibrary().contains(JVM_OKHTTP4) || getLibrary().contains(JVM_OKHTTP3));
     }
 
+    @Override
+    public Map<String, Object> postProcessModels(Map<String, Object> objs) {
+        Map<String, Object> objects = super.postProcessModels(objs);
+        @SuppressWarnings("unchecked") List<Object> models = (List<Object>) objs.get("models");
+
+        for (Object model : models) {
+            @SuppressWarnings("unchecked") Map<String, Object> mo = (Map<String, Object>) model;
+            CodegenModel cm = (CodegenModel) mo.get("model");
+
+            // escape the variable base name for use as a string literal
+            if (cm.requiredVars != null) {
+                for (CodegenProperty var : cm.requiredVars) {
+                    var.vendorExtensions.put(VENDOR_EXTENSION_BASE_NAME_LITERAL, var.baseName.replace("$", "\\$"));
+                }
+            }
+            if (cm.optionalVars != null) {
+                for (CodegenProperty var : cm.optionalVars) {
+                    var.vendorExtensions.put(VENDOR_EXTENSION_BASE_NAME_LITERAL, var.baseName.replace("$", "\\$"));
+                }
+            }
+        }
+
+        return objects;
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> objs, List<Object> allModels) {

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

@@ -3,10 +3,10 @@
 {{/description}}
     {{#jvm}}
     {{#moshi}}
-    @Json(name = "{{{baseName}}}")
+    @Json(name = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/moshi}}
     {{#gson}}
-    @SerializedName("{{name}}")
+    @SerializedName("{{{vendorExtensions.x-base-name-literal}}}")
     {{/gson}}
     {{/jvm}}
-    {{#multiplatform}}@SerialName(value = "{{baseName}}") {{/multiplatform}}val {{{name}}}: {{#isEnum}}{{#isListContainer}}{{#isList}}kotlin.collections.List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{classname}}.{{{nameInCamelCase}}}>{{/isListContainer}}{{^isListContainer}}{{classname}}.{{{nameInCamelCase}}}{{/isListContainer}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}? = {{#defaultvalue}}{{defaultvalue}}{{/defaultvalue}}{{^defaultvalue}}null{{/defaultvalue}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") {{/multiplatform}}val {{{name}}}: {{#isEnum}}{{#isListContainer}}{{#isList}}kotlin.collections.List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{classname}}.{{{nameInCamelCase}}}>{{/isListContainer}}{{^isListContainer}}{{classname}}.{{{nameInCamelCase}}}{{/isListContainer}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}? = {{#defaultvalue}}{{defaultvalue}}{{/defaultvalue}}{{^defaultvalue}}null{{/defaultvalue}}

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

@@ -3,10 +3,10 @@
 {{/description}}
     {{#jvm}}
     {{#moshi}}
-    @Json(name = "{{{baseName}}}")
+    @Json(name = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/moshi}}
     {{#gson}}
-    @SerializedName("{{name}}")
+    @SerializedName("{{{vendorExtensions.x-base-name-literal}}}")
     {{/gson}}
     {{/jvm}}
-    {{#multiplatform}}@SerialName(value = "{{baseName}}") @Required {{/multiplatform}}val {{{name}}}: {{#isEnum}}{{#isListContainer}}{{#isList}}kotlin.collections.List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{classname}}.{{{nameInCamelCase}}}>{{/isListContainer}}{{^isListContainer}}{{classname}}.{{{nameInCamelCase}}}{{/isListContainer}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required {{/multiplatform}}val {{{name}}}: {{#isEnum}}{{#isListContainer}}{{#isList}}kotlin.collections.List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{classname}}.{{{nameInCamelCase}}}>{{/isListContainer}}{{^isListContainer}}{{classname}}.{{{nameInCamelCase}}}{{/isListContainer}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}