React native : Failed to construct transformer: Error: Cannot create a string longer than 0x1fffffe8 characters

I've tried to log the file that causing the error, but console.log wasn't working. I come up with a quick hack to throw filePath then I've saw that a zip file, that I keeped as a backup, was the issue.

For some way react doesn't liked it so I have to move it outside of the project folder

I was running into the same problem.

 warning: the transform cache was reset.                                                                          
                 Welcome to React Native!                                                                        
                Learn once, write anywhere 
Failed to construct transformer:  Error: Cannot create a string longer than 0x1fffffe8 characters                
    at Object.slice (buffer.js:608:37)                                                                           
    at Buffer.toString (buffer.js:805:14)                                                                        
    at Object.readFileSync (fs.js:421:41)                                                                        
    at getContent (J:\expoProjects\rn-cnn\node_modules\metro\node_modules\jest-haste-map\build\worker.js:149:41) 
    at Object.<anonymous> (J:\expoProjects\rn-cnn\node_modules\metro\node_modules\jest-haste-map\build\worker.js:
199:9)                                                                                                           
    at Generator.next (<anonymous>)                                                                              
    at asyncGeneratorStep (J:\expoProjects\rn-cnn\node_modules\metro\node_modules\jest-haste-map\build\worker.js:
78:24)                                                                                                           
    at _next (J:\expoProjects\rn-cnn\node_modules\metro\node_modules\jest-haste-map\build\worker.js:98:9)        
    at J:\expoProjects\rn-cnn\node_modules\metro\node_modules\jest-haste-map\build\worker.js:103:7               
    at new Promise (<anonymous>) {                                                                               
  type: 'Error',                                                                                                 
  code: 'ERR_STRING_TOO_LONG'                                                                           

I solved the error by changing the node version to v14+ and then reverting back to the old version of node v10.15.3.

I've run into the exact same error. Turns out it was an auto-generated big file from gradle (> 700MB) inside "android.gradle\6.0.1\executionHistory"

For others having the same problem, and looking for a way to debug:

• Edit /node_modules/jest-haste-map/build/worker.js

• Wrap readFileSync in a try...catch, like this:

  const getContent = () => {
    if (content === undefined) {
      try {
        content = fs().readFileSync(filePath, 'utf8');
      } catch (err) {
        throw new Error(`error readFileSync ${filePath} : ${err.message}`);
      }
    }

    return content;
  };

• (re)start metro bundler:

/node_modules/react-native/scripts/launchPackager.command; exit

My output:

To reload the app press "r"
To open developer menu press "d"

Failed to construct transformer:  Error: error readFileSync <my project path>/some/big/file/that/caused/error : Cannot create a string longer than 0x1fffffe8 characters
    at getContent (<my project path>/node_modules/jest-haste-map/build/worker.js:133:15)
    at Object.worker (<my project path>/node_modules/jest-haste-map/build/worker.js:162:23)
    at execFunction (<my project path>/node_modules/jest-worker/build/workers/processChild.js:145:17)
    at execHelper (<my project path>/node_modules/jest-worker/build/workers/processChild.js:124:5)
    at execMethod (<my project path>/node_modules/jest-worker/build/workers/processChild.js:128:5)
    at process.messageListener (<my project path>/node_modules/jest-worker/build/workers/processChild.js:46:7)
    at process.emi

Hope this helps others having the same problem!

In my own case I noticed I was using an mp4 video file for my react native application which was too large in size. I had to delete it and that was the fix for me

It took me the whole day but I solved it. I still can't understand why I'm getting this error when I want to launch the app on iOS but:

removing the build directory in android/app fixed it.

To figure out what file caused an error I used @dirk approach. I don't sure why but my App_name.app.dSYM.zip became too large (536MB) so the node was unable to read it because of the 512MB limitation. It might be some different file in your case. Here is a patch-package to get more information about the file which caused this error

diff --git a/node_modules/jest-haste-map/build/worker.js b/node_modules/jest-haste-map/build/worker.js
index 1996d4a..1f17f11 100644
--- a/node_modules/jest-haste-map/build/worker.js
+++ b/node_modules/jest-haste-map/build/worker.js
@@ -146,7 +146,11 @@ function _worker() {
 
     const getContent = () => {
       if (content === undefined) {
-        content = _gracefulFs().default.readFileSync(filePath, 'utf8');
+        try {
+          content = _gracefulFs().default.readFileSync(filePath, 'utf8');
+        } catch (err) {
+          throw new Error(`error readFileSync ${filePath} : ${err.message}`);
+        }
       }
 
       return content;

Make sure you don't have any large files in your root project including (mp4, images, .zip, etc)?

In my case there was a zip file of whole project in the project directory which cause the issue when I remove it from the project directory and run

npm start --reset cache

it worked for me.

Moving any large asset files [pictures,videos,etc...] up out of the project directory. https://github.com/facebook/react-native/issues/28189#issuecomment-592918995

Check if there any unrelated file or zip in your project structure/folder if yes then delete file and error will be resolved