Fail-fast/pipefail behaviour for default shell inconsistent with documentation

Describe the bug The documentation states that

Fail-fast behavior using set -eo pipefail: Default for bash and built-in shell. It is also the default when you don’t provide an option on non-Windows platforms. (my emphasis)

The last statement does not appear to be true, as false | true passes on ubuntu-latest when not explicitly setting the shell option.

To Reproduce Steps to reproduce the behavior:

1. Run workflow file:

name: Test pipefail

on:
  push

jobs:
  test-pipefail:
    name: Test
    runs-on: ubuntu-latest
    steps:
      - name: Run command false first
        if: always()
        run: false | true
      
      - name: Run command false last
        if: always()
        run: true | false

1. Observe that only second step fails

Expected behavior I expect that the behaviour of the runner to be consistent with the documentation, ie. that both steps in the above example fails, or that the documentation is updated to reflect the actual behaviour.

Runner Version and Platform

Built in runner using ubuntu-latest

[eric-wieser]

I think there’s still a bug here; this page says that bash is the default shell, and that it is invoked with bash --noprofile --norc -eo pipefail {0}:

jobs.<job_id>.steps[*].shell

You can override the default shell settings in the runner’s operating system using the shell keyword. You can use built-in shell keywords, or you can define a custom set of shell options. The shell command that is run internally executes a temporary file that contains the commands specified in the run keyword.

Supported platform	shell parameter	Description	Command run internally
All	bash	The default shell on non-Windows platforms with a fallback to sh. When specifying a bash shell on Windows, the bash shell included with Git for Windows is used.	bash --noprofile --norc -eo pipefail {0}

I think that table should have an extra row called “(default)”, which is specified as bash -e {0}.

[MayCXC]

Hi, another thing that affects this, because the default/unspecified shell is bash -e with the errexit flag, this does result in fail fast behavior by default, which is not mentioned here: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#exit-codes-and-error-action-preference . Perhaps mentioning both would be clearest?