fix: use discriminated union for formatExceptionMessage to show render-specific label

Rendering callers now pass { renderingRequest } and get the original
"JS code for rendering request was:" label, while non-rendering callers
(upload-assets) pass { label, content } with an explicit label.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: AbanoubGhadban

packages/react-on-rails-pro-node-renderer/src/shared/utils.ts

@@ -58,15 +58,20 @@ export function errorResponseResult(msg: string, tracingContext?: TracingContext
   };
 }
 
+export type RequestInfo = { renderingRequest: string } | { label: string; content: string };
+
 /**
- * @param requestDescription A description of the request that caused the error (e.g. JS code or a task description)
+ * @param request Either a rendering request (auto-labeled) or a { label, content } pair
  * @param error The error that was thrown (typed as `unknown` to minimize casts in `catch`)
  * @param context Optional context to include in the error message
  */
-export function formatExceptionMessage(requestDescription: string, error: unknown, context?: string) {
+export function formatExceptionMessage(request: RequestInfo, error: unknown, context?: string) {
+  const label = 'renderingRequest' in request ? 'JS code for rendering request was:' : request.label;
+  const content = 'renderingRequest' in request ? request.renderingRequest : request.content;
+
   return `${context ? `\nContext:\n${context}\n` : ''}
-Request:
-${smartTrim(requestDescription)}
+${label}
+${smartTrim(content)}
 
 EXCEPTION MESSAGE:
 ${(error as Error).message || error}

packages/react-on-rails-pro-node-renderer/src/worker.ts

@@ -300,15 +300,15 @@ export default function run(config: Partial<Config>) {
           await setResponse(result, res);
         } catch (err) {
           const exceptionMessage = formatExceptionMessage(
-            renderingRequest,
+            { renderingRequest },
             err,
             'UNHANDLED error in handleRenderRequest',
           );
           await setResponse(errorResponseResult(exceptionMessage, context), res);
         }
       }, startSsrRequestOptions({ renderingRequest }));
     } catch (theErr) {
-      const exceptionMessage = formatExceptionMessage(renderingRequest, theErr);
+      const exceptionMessage = formatExceptionMessage({ renderingRequest }, theErr);
       await setResponse(errorResponseResult(`Unhandled top level error: ${exceptionMessage}`), res);
     }
   });
@@ -353,7 +353,7 @@ export default function run(config: Partial<Config>) {
 
         if (!wasLockAcquired) {
           const msg = formatExceptionMessage(
-            taskDescription,
+            { label: 'Request:', content: taskDescription },
             errorMessage,
             `Failed to acquire lock ${lockfileName}. Worker: ${workerIdLabel()}.`,
           );

packages/react-on-rails-pro-node-renderer/src/worker/handleRenderRequest.ts

@@ -42,7 +42,11 @@ async function prepareResult(
     let exceptionMessage = null;
     if (!result) {
       const error = new Error('INVALID NIL or NULL result for rendering');
-      exceptionMessage = formatExceptionMessage(renderingRequest, error, 'INVALID result for prepareResult');
+      exceptionMessage = formatExceptionMessage(
+        { renderingRequest },
+        error,
+        'INVALID result for prepareResult',
+      );
     } else if (isErrorRenderResult(result)) {
       ({ exceptionMessage } = result);
     }
@@ -65,7 +69,11 @@ async function prepareResult(
       data: result,
     };
   } catch (err) {
-    const exceptionMessage = formatExceptionMessage(renderingRequest, err, 'Unknown error calling runInVM');
+    const exceptionMessage = formatExceptionMessage(
+      { renderingRequest },
+      err,
+      'Unknown error calling runInVM',
+    );
     return errorResponseResult(exceptionMessage);
   }
 }
@@ -95,7 +103,7 @@ async function handleNewBundleProvided(
 
     if (!wasLockAcquired) {
       const msg = formatExceptionMessage(
-        renderingRequest,
+        { renderingRequest },
         errorMessage,
         `Failed to acquire lock ${lockfileName}. Worker: ${workerIdLabel()}.`,
       );
@@ -118,7 +126,7 @@ async function handleNewBundleProvided(
       const fileExists = await fileExistsAsync(bundleFilePathPerTimestamp);
       if (!fileExists) {
         const msg = formatExceptionMessage(
-          renderingRequest,
+          { renderingRequest },
           error,
           `Unexpected error when moving the bundle from ${providedNewBundle.bundle.savedFilePath} \
 to ${bundleFilePathPerTimestamp})`,
@@ -140,7 +148,7 @@ to ${bundleFilePathPerTimestamp})`,
         await unlock(lockfileName);
       } catch (error) {
         const msg = formatExceptionMessage(
-          renderingRequest,
+          { renderingRequest },
           error,
           `Error unlocking ${lockfileName} from worker ${workerIdLabel()}.`,
         );
@@ -258,7 +266,7 @@ export async function handleRenderRequest({
     return await prepareResult(renderingRequest, entryBundleFilePath);
   } catch (error) {
     const msg = formatExceptionMessage(
-      renderingRequest,
+      { renderingRequest },
       error,
       'Caught top level error in handleRenderRequest',
     );

packages/react-on-rails-pro-node-renderer/src/worker/vm.ts

@@ -153,7 +153,7 @@ ${smartTrim(renderingRequest)}`);
 
     if (isReadableStream(result)) {
       const newStreamAfterHandlingError = handleStreamError(result, (error) => {
-        const msg = formatExceptionMessage(renderingRequest, error, 'Error in a rendering stream');
+        const msg = formatExceptionMessage({ renderingRequest }, error, 'Error in a rendering stream');
         errorReporter.message(msg);
       });
       return newStreamAfterHandlingError;
@@ -172,7 +172,7 @@ ${smartTrim(result)}`);
 
     return result;
   } catch (exception) {
-    const exceptionMessage = formatExceptionMessage(renderingRequest, exception);
+    const exceptionMessage = formatExceptionMessage({ renderingRequest }, exception);
     log.debug('Caught exception in rendering request: %s', exceptionMessage);
     return Promise.resolve({ exceptionMessage });
   }