Git pre-received hook not failing with exit code 1 correcly

Marc C· Jan 21, 2024, 01:57 UTC · lore

Heya!

I am trying to understand why my pre-publish hook does not exit with the correct status code.

I have a pre-publish script

``` #!/bin/sh set -euo pipefail echo "Testing nixos config" nixos-rebuild dry-build echo "Success" ```

Running it directly in my CLI, it acts like I would expect and return exit code 1.

```
$ ./.git/hooks/pre-receive
Testing nixos config
building the system configuration...
error:
       … while calling the 'seq' builtin
       ....
       ...

$ echo "$?" 1 ```

However, when running the script as a pre-receive hook, it is not running the commands correctly and returns the wrong exit code. I get the following:

```
remote: Testing nixos config
remote: building the system configuration...
remote: Success <-- ????
remote: error:
remote:        … while calling the 'seq' builtin
...
To myserver:/myrepo
   bffa94e..a14b3f6  main -> main
```

Any clue what I am missing? When running it as a pre-receive hook, the failing command returns exit code 0. Running it in the CLI, it returns exit code 1. It is Schrodinger's exit code.

Thank you so much for your help.

Sincerely, Marc

brian m. carlson· Jan 21, 2024, 18:05 UTC · re: Marc C · lore

Re: Git pre-received hook not failing with exit code 1 correcly

On 2024-01-21 at 01:57:28, Marc C wrote:

> Heya!

Hey,

Show 8 quoted lines

> I am trying to understand why my pre-publish hook does not exit with the
> correct status code. 
> 
> I have a pre-publish script
> 
> ```
> #!/bin/sh
> set -euo pipefail

One note about this is that `-o pipefail` is a bash- and zsh-specific option. (It's also present in some ksh variants.) It isn't specified by POSIX, so you'd probably want to use `#!/bin/bash` as your shebang instead.

Even OSes such as Debian which specify certain extensions required for `/bin/sh` (notably `local`) don't require this of it.

Show 18 quoted lines

> However, when running the script as a pre-receive hook, it is not
> running the commands correctly and returns the wrong exit code. I get
> the following:
> 
> ```
> remote: Testing nixos config
> remote: building the system configuration...
> remote: Success <-- ????
> remote: error:
> remote:        … while calling the 'seq' builtin
> ...
> To myserver:/myrepo
>    bffa94e..a14b3f6  main -> main
> ```
> 
> Any clue what I am missing? When running it as a pre-receive hook, the
> failing command returns exit code 0. Running it in the CLI, it returns
> exit code 1. It is Schrodinger's exit code.

I know nothing about nixOS, but I'm wondering if maybe `nixos-rebuild dry-build` forks in some cases, specifically when it's detached from the terminal. If that happened, then you'd see the above, where the child process continued but the parent process exited, and then the error message would get printed at the end.

You'd also see this if you had an `&` at the end of `nixos-rebuild dry-build`, but you don't seem to have that here.

You could try something like `(cat | ./.git/hooks/pre-receive 2>&1 | cat)` to see if the problem is the lack of terminal.

Hopefully that gives you a helpful head start on the problem. I apologize for not being able to help more.

-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA