Debugger isn't stopped at the `debugger;` statement when debugging using `--inspect`

[arcanis]

Note: previous thread was #10457, but it got closed recommending --inspect-brk which is more a workaround than a solution imo.

Is your feature request related to a problem? Please describe.

When debugging a CLI program, I want to break at a specific location. For DevX reasons I don't want to use --inspect-brk, as it would require me to attach the debugger before even knowing whether the codepath covered by the breakpoint is hit - which is particularly cumbersome when using nested processes (with --inspect-port=0).

Describe the solution you'd like

I'd like debugger; statements to pause the execution even if a debugger isn't attached yet; I'd then attach it myself.

Describe alternatives you've considered

Pausing the process manually using execSync w/ sleep or similar doesn't work: the debugger doesn't see the Node process. I suspect an internal integration is required for the process to answer the debugger during a synchronous call?

[june07]

So I just completed a feature of NiM that partially addresses this issue. Using the underlying devtools protocol NiM will resume the debugger (past --inspect-brk) automatically when it connects...

Granted, situations where you're assigning random ports via "=0" will require more, but maybe this would help in certain other situations.

[schalkneethling]

I ran into this same problem. In the curriculum used by the Linux Foundation to prepare you for the Nodejs application developer exam, it is stated that --inspect-brk will stop the debugger at the first executable line. 👍

When using debugger; the material says to use --inspect instead of --inspect-brk as the former will execute the program and then pause at the debugger; line. This is not the case, as the program executes to its conclusion without pausing.

One can use inspect-brk as a workaround (as mentioned by @arcanis), but it sounds like the documentation is unclear on whether there is a use case where one would favor --inspect over --inspect-brk.

[bnoordhuis]

I'd like debugger; statements to pause the execution even if a debugger isn't attached yet

I think you can already kind of do that with a preload script: node --inspect -r preload.js app.js

Load the inspector module and start listening for breakpoint events (debugger statements are breakpoints), then call inspector.waitForDebugger() when you receive one.