Initialize config-customized mustache compiler only once

Author: jimschubert

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

@@ -708,9 +708,7 @@ private void generateSupportingFiles(List<File> files, Map<String, Object> bundl
                 }
 
                 if (ignoreProcessor.allowsFile(new File(outputFilename))) {
-                    if (Arrays.stream(templatingEngine.getFileExtensions())
-                            .anyMatch(templateFile::endsWith)) {
-                        configPostProcessMustacheCompiler();
+                    if (Arrays.stream(templatingEngine.getFileExtensions()).anyMatch(templateFile::endsWith)) {
                         String templateContent = templatingEngine.compileTemplate(this, bundle, support.templateFile);
                         writeToFile(outputFilename, templateContent);
                         File written = new File(outputFilename);
@@ -890,6 +888,9 @@ public List<File> generate() {
         configureGeneratorProperties();
         configureOpenAPIInfo();
 
+        // If the template adapter is mustache, we'll set the config-modified Compiler.
+        configPostProcessMustacheCompiler();
+
         List<File> files = new ArrayList<File>();
         // models
         List<String> filteredSchemas = ModelUtils.getSchemasUsedOnlyInFormParam(openAPI);
@@ -918,7 +919,6 @@ public String getFullTemplateContents(String templateName) {
     protected File processTemplateToFile(Map<String, Object> templateData, String templateName, String outputFilename) throws IOException {
         String adjustedOutputFilename = outputFilename.replaceAll("//", "/").replace('/', File.separatorChar);
         if (ignoreProcessor.allowsFile(new File(adjustedOutputFilename))) {
-            configPostProcessMustacheCompiler();
             String templateContent = templatingEngine.compileTemplate(this, templateData, templateName);
             writeToFile(adjustedOutputFilename, templateContent);
             return new File(adjustedOutputFilename);

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

@@ -544,6 +544,7 @@ public ClientOptInput toClientOptInput() {
             config.setLibrary(library);
         }
 
+        // Built-in templates are mustache, but allow users to use a simplified handlebars engine for their custom templates.
         if (isEmpty(templatingEngineName) || templatingEngineName.equals("mustache")) {
             config.setTemplatingEngine(new MustacheEngineAdapter());
         } else if (templatingEngineName.equals("handlebars")) {