Add ability to disable break on first line when using the CLI inspector

[Spakman]

Is your feature request related to a problem? Please describe.
I use Node.js to run unit tests in a (Linux) shell. The way this is set up to run is to evaluate each test script as a single invocation of Node.js in series. It's working great!

However, while I do have the ability to use a debugger; statement (when I invoke each test using node inspect a_test_file.js) in these scripts to use the built-in CLI inspector, because of the forced breakpoint on the first line, the debug shell is activated for every test script, which quickly becomes tedious. I'm looking to run something like node inspect a_test_file.js and only have it bring up the debug shell if/when a debugger; statement is executed.

Describe the solution you'd like
While I do understand the need to break on the first line in many other situations, some method to disable it would be very useful in this circumstance. An environment varible or a command line argument to achieve this would both work well for me.

Describe alternatives you've considered
I'm not aware of any way to work around this.

[Trott]

@nodejs/diagnostics

[RafaelGSS]

I'm generally +1 on this.

[Trott]

I guess the obvious way to implement this would be as a command-line flag: node inspect --run index.js or node inspect --no-break-on-first-line index.js or something like that. Is there a better/preferable way?

[RafaelGSS]

I'm thinking in disable by default the break on first line and land it as major. What do you think? @Trott

[Trott]

I'm thinking in disable by default the break on first line and land it as major. What do you think? @Trott

Does that conflict with the behavior most people would want and expect? Do CLI debuggers in general tend to break on or before the first executable statement by default? I'd be interested to know what the standard Python, Perl, and Ruby CLI debuggers do, for example.

[Trott]

python -m pdb script.py appears to break on the first line by default.

I suspect Perl and Ruby and interpreted/scripting languages in general do the same in their CLI debuggers, but correction is welcome.

I personally would find a different behavior (in a CLI debugger) surprising, but I'm certainly open to the idea if it's the right thing to do.

[targos]

I would be -1 on making it the default. I don't think having debugger; statements in the code is the common use case.

[targos]

Btw, I think we should still always break internally on first line, because otherwise there's a risk that the code with the breakpoint runs before we connect the inspector. An option to automatically continue after this initial pause SGTM.

[RafaelGSS]

Btw, I think we should still always break internally on first line, because otherwise there's a risk that the code with the breakpoint runs before we connect the inspector. An option to automatically continue after this initial pause SGTM.

Yes, makes sense.

[Trott]

It looks like there is already an undocumented environment variable that does this. Set NODE_INSPECT_RESUME_ON_START=1 and it should not break on the first line.

@Spakman Can you test this and confirm that it works as you expect?

If so, perhaps the solution is to document the environment variable.