Conditional operator or function for expression syntax

[StephenCleary]

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.

[ylemkimon]

Another alternative syntax could be:

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

like CircleCI.

[ylemkimon]

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

[molszanski]

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