Why does the bash example (https://github.com/pantsbuild/example-plugin/tree/main/pants-plugins/examples/bash) uses

Process

and not

InteractiveProcess

?

Which part of the example? Generally, the default is to use Process because it allows for caching and concurrency. InteractiveProcess is intended for when it needs to run in the foreground so that the user can write to stdin, such as using a debugger

Isn't a REPL always interactive? I think I need to re-read the docs. I thought

Process

would be used to run the bash executable. But in

pants-plugins/examples/bash/bash_setup.py

I see that is not the case. Instead the

BinaryPaths

,

BinaryPathRequest

and

BashProgram

are all that is required to execute the bash repl. Does

exe: str

tell the Rust engine to "execute the binary passed to this class? In this case

bash_program_paths.first_path.path

.

Isn’t a REPL always interactive?

Indeed. But Jupyter is interesting because you’re not necessarily typing into the console like a normal REPL. I think you would still use

InteractiveProcess

, though, so that you have in the foreground its message about starting up and where to open the page. — Ah, I can see how that’s confusing.

bash_setup.py

only exists for utils used by the other rules. Under-the-hood, the rule for

BinaryPathRequest -> BinaryPaths

is running a

Process

to discover where on your machine the program is installed. This path is getting stored as

BashProgram.exe

, which is solely a string representing the absolute path to, say,

/bin/bash

. Then, you can use that in your other processes to set argv to be

[/bin/bash, my_script.sh]

, for example. Rather than hardcoding

/bin/bash

,

BinaryPaths

is finding `bash`’s absolute path for you. — In

repl.py

, you’re not seeing

InteractiveProcess

or

Process

anywhere because that gets handled by

core/goals/repl.py

. All your plugin does is give information needed by

core/goals/repl.py

to set up that

InteractiveProcess

. If you were to do your own new

jupyter

goal—rather than hooking into `repl`—then you would end up using

InteractiveProcess

.