Environment vars are not correctly evaluated in a jobs if condition

[christianfroehlich]

Why are you starting this discussion?

Bug

What GitHub Actions topic or product is this about?

Workflow Deployment

Discussion Details

I am trying to use github actions environment variables as as feature toggles to limit the deployment of certain features to certain environments during development without requiring hard-coding the feature toggle either in the workflow or within the code itself.

We have multiple environments, but for this example lets assume we only have a development (dev) and production environment, and each environment has a variable named "DEPLOY" which has a value of either "Y" or "N".

From my testing the condition can only be correctly evaluated if the variable is wrapped in the curly braces, e.g. if: ${{ vars.DEPLOY }} == 'Y'. However it does not work if the curly braces are omitted (as it typical for a job if condition) or if the condition is wrapped in curly braces in its entirety.
This behaviour is not intuitive, is not documented and appears to be a bug. I can only assume that the variable is not otherwise available at the time of evaluation of the job's if condition, and the behaviour gets stranger if you try and combine it with other if conditions.

e.g. given the following workflow, run on push on the test-feature-toggle branch, with the DEPLOY variable defined for the dev environment and set to Y:

name: Test Feature Toggle Conditions

on:
  push:    
    branches:      
      - "test-feature-toggle"

jobs:
  fully-wrapped-single-condition:
    if: ${{ vars.DEPLOY == 'Y' }}
    environment:
      name: dev
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"   

  partially-wrapped-single-condition:
    if: ${{ vars.DEPLOY }} == 'Y'
    environment:
      name: dev
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"

  unwrapped-single-condition:
    if: vars.DEPLOY == 'Y'
    environment:
      name: dev
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"

  fully-wrapped-double-condition:
    if: ${{ vars.DEPLOY == 'Y' && github.ref_name == 'test-feature-toggle' }}
    environment:
      name: dev
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"
  
  partially-wrapped-double-condition:
    if: ${{ vars.DEPLOY }} == 'Y' && ${{ github.ref_name == 'test-feature-toggle' }}
    environment:
      name: dev
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"

  unwrapped-double-condition:
    if: vars.DEPLOY == 'Y' && github.ref_name == 'test-feature-toggle'
    environment:
      name: dev 
    runs-on: ubuntu-latest
    steps:
      - run: echo "DEPLOY == ${{ vars.DEPLOY }}"

Yields the following results:

Based on the documentation it would reasonably be assumed that most if not all of these conditions would evaluate to true.

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