How do I debug system_binary?

system_binary(
    name="git",
    binary_name="git",
)

Leads to

pants run .build:build-libcamera
17:37:36.50 [INFO] Completed: Testing candidate for `git` at `/bin/git`
17:37:36.50 [INFO] Completed: Testing candidate for `git` at `/usr/bin/git`
17:37:36.51 [ERROR] 1 Exception encountered:

Engine traceback:
  in `run` goal

ValueError: Could not find a binary with name `git`. The following paths were searched: /usr/bin, /bin, /usr/local/bin, /opt/homebrew/bin.

But..

which git
/usr/bin/git

Add

--keep-sandboxes=always

and see for yourself what "Testing candidate for

git

at `/usr/bin/git`" sees,

Hmm looks normal?

pants run .build:libcamera --keep-sandboxes=always
17:52:03.84 [INFO] Initialization options changed: reinitializing scheduler...
17:52:08.36 [INFO] Scheduler initialized.
17:52:08.47 [INFO] Preserving local process execution dir /tmp/pants-sandbox-5nreNe for Searching for `bash` on PATH=/usr/bin:/bin:/usr/local/bin
17:52:08.51 [INFO] Preserving local process execution dir /tmp/pants-sandbox-gSV1Op for Test binary /usr/bin/bash.
17:52:08.51 [INFO] Preserving local process execution dir /tmp/pants-sandbox-KntnE3 for Test binary /bin/bash.
17:52:08.57 [INFO] Preserving local process execution dir /tmp/pants-sandbox-Ee4YW5 for Searching for `git` on PATH=/usr/bin:/bin:/usr/local/bin:/opt/homebrew/bin
17:52:08.61 [INFO] Preserving local process execution dir /tmp/pants-sandbox-Ce8jj4 for Testing candidate for `git` at `/bin/git`
17:52:08.61 [INFO] Preserving local process execution dir /tmp/pants-sandbox-usMJKB for Testing candidate for `git` at `/usr/bin/git`
17:52:08.80 [INFO] Completed: Testing candidate for `git` at `/bin/git`
17:52:08.80 [INFO] Completed: Testing candidate for `git` at `/usr/bin/git`
17:52:08.82 [ERROR] 1 Exception encountered:

Engine traceback:
  in `run` goal

ValueError: Could not find a binary with name `git`. The following paths were searched: /usr/bin, /usr/bin, /bin, /usr/local/bin, /opt/homebrew/bin.

Preserving local process execution dir /tmp/pants-sandbox-usMJKB for Testing candidate for `git` at `/usr/bin/git`

So cd to

/tmp/pants-sandbox-usMJKB

Ahhh neat!

What does Pants try though? Not

git

presumably

git --version

or something?

Well I had

system_binary(
    name="git",
    binary_name="git",
)

Or is this you?

It just tried /usr/bin/git, which returns 1

Almost certainly there is a place to configure a test.

Yeah we can add the fingerprint_args to get it to work, then test it too for versions

So what is the contents of

__run.sh

exactly?

It was

cat __run.sh 
#!/bin/bash
# This command line should execute the same process as pants did internally.
export 
cd /tmp/pants-sandbox-usMJKB
/usr/bin/git

Ok, yeah. So I'm surprised this works for people generally. It seems to me most tools error when invoked with no args - but maybe not.

Yeah. I hit it with npm last night.. same thing returns exit code of 1

Ok, that seems like a wart to me then in this whole mechanism. That said I have not gone and read high-level docs - maybe this is spelled out.

I've tripped over this too. I filed https://github.com/pantsbuild/pants/issues/19013

Actually I can't get this to work..

system_binary(
    name="npm",
    binary_name="npm",
    fingerprint=r"9.2.0",
    fingerprint_args=["--version"],
)

cat /tmp/pants-sandbox-MjbXO2/__run.sh 
#!/bin/bash
# This command line should execute the same process as pants did internally.
export 
cd /tmp/pants-sandbox-MjbXO2
/usr/bin/npm --version

pants run teletom/frontend:npm --keep-sandboxes=always
17:52:33.49 [INFO] Preserving local process execution dir /tmp/pants-sandbox-ewKBkO for Testing candidate for `npm` at `/bin/npm`
17:52:33.49 [INFO] Preserving local process execution dir /tmp/pants-sandbox-MjbXO2 for Testing candidate for `npm` at `/usr/bin/npm`
17:52:33.55 [INFO] Completed: Testing candidate for `npm` at `/bin/npm`
17:52:33.55 [INFO] Completed: Testing candidate for `npm` at `/usr/bin/npm`
17:52:33.55 [ERROR] 1 Exception encountered:

Engine traceback:
  in `run` goal

ValueError: Could not find a binary with name `npm` with output matching `9.2.0` when run with arguments `--version`. The following paths were searched: /usr/bin, /bin, /usr/local/bin, /opt/homebrew/bin.

bash /tmp/pants-sandbox-MjbXO2/__run.sh | tail
declare -x XDG_RUNTIME_DIR="/run/user/1000"
declare -x XDG_SEAT="seat0"
declare -x XDG_SESSION_CLASS="user"
declare -x XDG_SESSION_DESKTOP="i3"
declare -x XDG_SESSION_ID="3"
declare -x XDG_SESSION_TYPE="x11"
declare -x XDG_VTNR="2"
declare -x XMODIFIERS="@im=ibus"
declare -x _="/usr/bin/bash"
9.2.0

echo $?
0

Did you mess with fingerprint? Add a newline etc?

like add a \n? 🤔

Yes!!!

There are no newlines or tabs 😾

So you actually tried

fingerprint_args=["--version\n"],

?

Oh I was trying on fingerprint regex

Sorry - typo, but you see what I mean?

Two potential sources of issues 1. The

fingerprint

is matched with

re.match

, i.e. needs to be at the start. 2. in 2.16

__run.sh

isn't fully hermetic and leaks env vars from your shell, so the behaviour inside pants may be different to running it outside I think 2 might be the problem here:

npm

needs

node

available to run, and so the

fingerprint_dependencies=[...]

field will need to include a

node

system_binary

Ahhh good call on node

system_binary(
    name="npm",
    binary_name="npm",
    fingerprint=r"9.2.0",
    fingerprint_args=["--version"],
    fingerprint_dependencies=[":node"],
)