Conditional operator or function for expression syntax · Issue #409 · actions/runner · GitHub
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Conditional operator or function for expression syntax #409

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Conditional operator or function for expression syntax#409
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AllanGuigou

Description

@StephenCleary
StephenCleary
opened on Apr 6, 2020

Describe the enhancement

I'd like some kind of conditional operation added to expression syntax. This can be an actual ternary operator (? :) or a built-in function (e.g., if(<condition>, <true-value>, <false-value>)).

Additional information

There is a workaround: using shell scripts to evaluate the condition, setting step outputs, and having other steps reference those outputs. But it would be much cleaner to have some kind of ternary / if/then/else / conditional branching built in to the expression syntax.

Activity

  1. StephenCleary
    added
    enhancementNew feature or request
    on Apr 6, 2020
  2. StephenCleary
    changed the title [-]Conditional operator or function[/-] [+]Conditional operator or function for expression syntax[/+] on Apr 6, 2020
  3. TingluoHuang
    added
    runner
    service
    Actions FeatureFeature requires both runner, pipelines service and launch changes
    and removed
    enhancementNew feature or request
    runner
    service
    on Jun 8, 2020

  4. ylemkimon commented on Aug 16, 2020

    @ylemkimon
    ylemkimon
    on Aug 16, 2020

    Another alternative syntax could be:

    ${{ if(condition) }} evaluateIfTrue ${{ else }} evaluateIfFalse ${{ endif }}

    like CircleCI.

  5. ylemkimon commented on Nov 15, 2020

    @ylemkimon
    ylemkimon
    on Nov 15, 2020

    It seems, although not identical, <condition> && <true-value> || <false-value> works in most cases.

  6. molszanski commented on Dec 30, 2020

    @molszanski
    molszanski
    on Dec 30, 2020

    Syntax: ${{ x && 'ifTrue' || 'ifFalse' }}

    fake ternary example

        steps:
      - name: stuff
        env:
          PR_NUMBER_OR_MASTER: ${{ github.event.number == 0 && 'master' ||  format('pr-{0}', github.event.number)  }}

    on condition is that your first <true-value> must be true for this to work

  7. ageorgou
    added a commit that references this issue on Jun 17, 2021

    Use correct compiler command

    f625056
  8. ageorgou
    added a commit that references this issue on Jun 29, 2021

    Include Intel compiler and MPI in CI (#36)

    2652c80

  9. TWiStErRob commented on Jul 17, 2021

    @TWiStErRob
    TWiStErRob
    on Jul 17, 2021

    Example use case https://github.com/TWiStErRob/net.twisterrob.gradle/pull/136/files
    Related StackOverflow: https://stackoverflow.com/a/68422069/253468

  10. LaPeste commented on Aug 26, 2021

    @LaPeste
    LaPeste
    on Aug 26, 2021

    The fact that in a year no one said a word about this, means that the team isn't interested in following up on this one?

  11. 34 remaining items

  12. bthomee
    added a commit that references this issue on Jul 30, 2025

    GitHub ternary operator doesn't handle the empty string (#10)

    83fe331
  13. torben-hansen
    added a commit that references this issue on Sep 4, 2025

    Fix ternary operator in github workflow (#2653)

    bce4b52
  14. ericsciple
    reopened this on Jan 7, 2026
  15. ericsciple
    assigned
    AllanGuigou
    on Jan 7, 2026
  16. github-actions
    removed
    actions-feature
    on Jan 8, 2026

  17. salilsub commented on Jan 30, 2026

    @salilsub
    salilsub
    on Jan 30, 2026

    Hi everyone, we just announced our new case function which is adds conditionals for expressions.

  18. lpulley commented on Jan 30, 2026

    @lpulley
    lpulley
    on Jan 30, 2026

    BTW it seems that this example from the case docs is not valid YAML:

    env:
  MY_ENV_VAR: ${{ case(
    github.ref == 'refs/heads/main', 'production',
    github.ref == 'refs/heads/staging', 'staging',
    startsWith(github.ref, 'refs/heads/feature/'), 'development',
    'unknown'
  ) }}

    The ) }} is not indented, so is not considered part of the MY_ENV_VAR value. Maybe this, with double quotes?

    env:
  MY_ENV_VAR: "${{ case(
    github.ref == 'refs/heads/main', 'production',
    github.ref == 'refs/heads/staging', 'staging',
    startsWith(github.ref, 'refs/heads/feature/'), 'development',
    'unknown'
  ) }}"

  19. lpulley commented on Jan 30, 2026

    @lpulley
    lpulley
    on Jan 30, 2026

    Also, I'm seeing errors like this when using non-boolean values as predicates in case:

    The workflow is not valid. Error when evaluating 'run-name'. .github/workflows/my-workflow.yml (Line: 2, Col: 11): Error from function 'case': case predicate must evaluate to a boolean value

    but the expressions docs say:

    Note that in conditionals, falsy values (false, 0, -0, "", '', null) are coerced to false and truthy (true and other non-falsy values) are coerced to true.

    Is there a reason that case doesn't coerce non-falsy values to true?

  20. AllanGuigou commented on Jan 30, 2026

    @AllanGuigou
    AllanGuigou
    on Jan 30, 2026
    Contributor

    @lpulley we've fixed the invalid YAML in the docs,

    env:
  MY_ENV_VAR: |-
    ${{ case(
      github.ref == 'refs/heads/main', 'production',
      github.ref == 'refs/heads/staging', 'staging',
      startsWith(github.ref, 'refs/heads/feature/'), 'development',
      'unknown'
    ) }}

    Thanks for calling that out!

    As for the boolean values, we intentionally require predicates to be booleans to avoid common failure scenarios that unintentionally or incorrectly rely on falsy coercions. I'll take a look to see how we can improve the docs in regards to that as well.

  21. lpulley commented on Jan 30, 2026

    @lpulley
    lpulley
    on Jan 30, 2026

    I see. I know an input (inputs context in workflows & actions) with no default value is falsy if it is not provided; is it equal to the empty string? In other words: instead of case(inputs.maybe-this-input-was-provided, 'thing A', 'thing B'), I should do case(inputs.maybe-this-input-was-provided != '', 'thing A', 'thing B')?

  22. ericsciple commented on Mar 10, 2026

    @ericsciple
    ericsciple
    on Mar 10, 2026
    Collaborator

    @lpulley 👍 the empty string check should work since empty string is also falsy

  23. ericsciple commented on Mar 10, 2026

    @ericsciple
    ericsciple
    on Mar 10, 2026
    Collaborator

    Closing this issue since the case function is released:

  24. ericsciple
    closed this as completedon Mar 10, 2026
  25. pull
    added a commit that references this issue on May 11, 2026

    chore: use GitHub case syntax instead of ternary "if" (dfinity#10139)

    371ec23
  26. zeekay
    added a commit that references this issue on Jul 26, 2026

    Don't pass --fail-commands-not-all-hit to validator if we don't run t…

    63b863d
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