better operationId in elm client generator (#8109)

Author: wing328

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

@@ -23,6 +23,7 @@
 import com.samskivert.mustache.Template;
 import io.swagger.v3.oas.models.media.ArraySchema;
 import io.swagger.v3.oas.models.media.Schema;
+import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.*;
 import org.openapitools.codegen.meta.features.*;
 import org.openapitools.codegen.utils.ModelUtils;
@@ -37,6 +38,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 
 public class ElmClientCodegen extends DefaultCodegen implements CodegenConfig {
@@ -174,6 +176,31 @@ public String escapeQuotationMark(String input) {
         return input.replace("\"", "");
     }
 
+    @Override
+    public String toOperationId(String operationId) {
+        // throw exception if method name is empty
+        if (StringUtils.isEmpty(operationId)) {
+            throw new RuntimeException("Empty method/operation name (operationId) not allowed");
+        }
+
+        operationId = camelize(sanitizeName(operationId), true);
+
+        // method name cannot use reserved keyword, e.g. return
+        if (isReservedWord(operationId)) {
+            String newOperationId = camelize("call_" + operationId, true);
+            LOGGER.warn(operationId + " (reserved word) cannot be used as method name. Renamed to " + newOperationId);
+            return newOperationId;
+        }
+
+        // operationId starts with a number
+        if (operationId.matches("^\\d.*")) {
+            LOGGER.warn(operationId + " (starting with a number) cannot be used as method sname. Renamed to " + camelize("call_" + operationId), true);
+            operationId = camelize("call_" + operationId, true);
+        }
+
+        return operationId;
+    }
+
     @Override
     public String toApiName(String name) {
         if (name.length() == 0) {