How can I create a custom failure message for a task?

[jayhendren]

How can I create a custom failure message for a task?

As a simplified example, let's say I'm creating a task that checks for uncommitted changes in a repo. My task looks like this:

  check_uncommitted:
    desc: Check that there are no uncommitted changes
    cmd: '[ -z "$(git status --porcelain)" ]'

Functionally, this works fine. If there are uncommitted changes in the repo, the task fails like so:

$ task check_uncommitted
task: [check_uncommitted] [ -z "$(git status --porcelain)" ]
task: Failed to run task "check_uncommitted": exit status 1

However, I find the failure message in this case to be a little bit opaque; I don't believe it's clear to the user what specific conditions caused this task to fail. I would prefer for the output to say something along the lines of "You appear to have uncommitted changes in your repository. Please commit your changes and try again." Is there a Taskfile-idiomatic way of printing custom output upon task failure?

[jayhendren]

Aha, I think I found a workable solution. It feels a little clunky, but it seems to work. I'm happy to hear other suggestions as well.

  check_uncommitted:
    desc: Check that there are no uncommitted changes
    silent: true
    if: '[ ! -z "$(git status --porcelain)" ]'
    vars:
      MSG: |-
        You appear to have uncommitted changes.
        Please commit your changes and try again.

        Uncommitted changes:
    cmds:
      - "echo '{{.MSG}}'"
      - git status --porcelain
      - false

Output:

$ task check_uncommitted
You appear to have uncommitted changes.
Please commit your changes and try again.

Uncommitted changes:
 M Taskfile.yml
task: Failed to run task "check_uncommitted": exit status 1

[jayhendren]

Ahh, here we go. This is much better. The combo of defer + silent + .EXIT_CODE got me there:

  check_uncommitted:
    desc: Check that there are no uncommitted changes
    vars:
      MSG: |
        You appear to have uncommitted changes.
        Please commit your changes and try again.
    cmds:
      - defer: "echo -n '{{if .EXIT_CODE}}{{.MSG}}{{end}}'"
        silent: true
      - '[ -z "$(git status --porcelain)" ]'

Output:

$ task check_uncommitted
task: [check_uncommitted] [ -z "$(git status --porcelain)" ]
You appear to have uncommitted changes.
Please commit your changes and try again.
task: Failed to run task "check_uncommitted": exit status 1

[vmaerten]

You can use preconditions : https://taskfile.dev/docs/guide#using-programmatic-checks-to-cancel-the-execution-of-a-task-and-its-dependencies with a proper msg

[jayhendren]

Oh, I didn't see that possibility! Yes, that would work too, and certainly makes the Taskfile clearer in terms of design intent. Interesting that preconditions support msg, but cmd, if, etc. do not.

  check_uncommitted:
    desc: Check that there are no uncommitted changes
    vars:
      CMD: "git status --porcelain"
      CHANGES: {sh: "{{.CMD}}"}
      MSG: |
        You appear to have uncommitted changes.
        Please commit your changes and try again.

        Uncommitted changes:
        {{.CHANGES}}
    preconditions:
      - sh: '[ -z "{{.CHANGES}}" ]'
        msg: "{{.MSG}}"

$ task check_uncommitted
task: You appear to have uncommitted changes.
Please commit your changes and try again.

Uncommitted changes:
 M Taskfile.yml

task: Failed to run task "check_uncommitted": task: precondition not met