Display PID of other running SwiftPM processes

[louisunlimited]

Displays the PID of the other SwiftPM instance currently holding the lock

Motivation:

• Fixes Display the process ID in the when running a Swift PM command that has a hold of the .build directory #8528

When we try to run different SwiftPM processes we already see notes like

Another instance of swiftPM is already running using '/Users/louissssss/swift-package-manager/.build', waiting until that process has finished execution...

I'll be nice to also have info about PID so I can choose to terminate it or wait for it to finish, so it might display smt like:

Another instance of SwiftPM (PID: 3404) is already running using '/Users/louissssss/swift-package-manager/.build', waiting until that process has finished execution...

Modifications:

My approach was trying to write process id from the process that acquires the lock to the lock file and then let other processes read from it and get the pid.

Result:

If another SwiftPM process is currently running, it now displays:

Another instance of SwiftPM (PID: 3404) is already running using '/Users/louissssss/swift-package-manager/.build', waiting until that process has finished execution...

[jakepetroules]

I'd add a space after the closing parenthesis, like so:

let pidInfo = lockingPID.map { "(PID: \($0)) " } ?? ""

...and then correspondingly remove the space after the pifInfo interpolation a few lines down, like so:

"Another instance of SwiftPM \(pidInfo)is already running using '\(self.scratchDirectory)', but this will be ignored since `--ignore-lock` has been passed"

...so that we don't end up with a double space between "SwiftPM" and "is" if we couldn't read the PID, since that would look out of place.

[jakepetroules]

Thanks for your PR, this is a nice little enhancement! Just had some minor formatting related-feedback.

[plemarquand]

nit: refactor out self.scratchDirectory.appending(".lock").pathString in to a variable

[louisunlimited]

Just did all the changes, one other thought: would it be better if we mark String(pid).write(toFile: lockFile, atomically: true, encoding: .utf8) with try? instead of try so this is not a critical throw and will not stop the program? I'd say as long as we can acquire the lock we should not interrupt normal execution.

[plemarquand]

@louisunlimited I think that's a good idea. It's a non-essential call and worst case the message just falls back to what we have today.

[louisunlimited]

@louisunlimited I think that's a good idea. It's a non-essential call and worst case the message just falls back to what we have today.

Cool, just pushed the changes, lmk if you need me for anything else

[plemarquand]

@swift-ci test

[johnbute]

Great pr Louis! I was working on the same thing too:

#8618

If you want to take any changes from it to enhance yours please do :)