How to start jscodeshift in inspect mode?

Question

This used to be runnable but recently I'm encounter the following issue.

By running the following command:

node --inspect-brk ./node_modules/.bin/jscodeshift mod.js file.

I am encountering this problem

Debugger listening on ws://127.0.0.1:9229/7e57a2d3-0885-44b3-b51e-b47dc8417d87
For help, see: https://nodejs.org/en/docs/inspector
Debugger attached.
Processing 1 files... 
Spawning 1 workers...
Sending 1 files to free worker...
Starting inspector on 127.0.0.1:9229 failed: address already in use
All done. 
Results: 
0 errors
0 unmodified
0 skipped
0 ok
Time elapsed: 0.035seconds 

Answer 1

The reason inspect mode doesn't work is because another process (e.g. another instance of the inspector) is already using the default port (9229), so they're conflicting. Either use a different port for the inspector or kill the process that's currently using the port.

If you use a different port, you'll be able to start the inspector. Just pass the desired port-number (e.g. 39479) to --inspect-brk.

Your example: node --inspect-brk ./node_modules/.bin/jscodeshift mod.js file.

Could for example be: node --inspect-brk=39479 ./node_modules/.bin/jscodeshift mod.js file.

DANGER: If you need the port 9229, you can kill the process/inspector that's currently using that port, but if you don't know what that process is doing you could damage things: lsof -i TCP:9229 | grep LISTEN | awk '{print $2}' | xargs kill -9

Answer 2

What worked for me:

1. Start node-inspector
2. Install jscodeshift in my local repo as a dev dependency.
3. put debugger statement in my script

4. run jscodeshift via node with --debug-brk arg and added --run-in-band jscodeshift param. For example :- I entered node

   --debug-brk ./node_modules/jscodeshift/bin/jscodeshift.sh -t my-refactor-script.js --run-in-band

If you add a file pattern at the end, it works fine, which in the case of debugging is helpful when you want to test just one trouble file.

I did not test debugging jscodeshift installed via npm -g

Answer 3

The answer that worked for me was installing ndb, https://github.com/GoogleChromeLabs/ndb, and prefixing the command with it.

ndb node --inspect-brk ./node_modules/.bin/jscodeshift mod.js