I’m trying to understand boolean expressions in GitHub actions. The documentation gives the following example of literals of different types, including boolean as ${{ false }} and ${{ true }}.

Following their lead I use the following step with an env section that sets VARF to false and VART to true and then in the run key has some test output:

  - name: Var test
    env:
      VARF: ${{ false }}
      VART: ${{ true }}
    run: |
      echo "VART=${{ env.VARF }}"
      echo "VART=${{ env.VART }}"
      echo "VARF && VART=${{ env.VARF && env.VART }}"
      echo "VARF || VART=${{ env.VARF || env.VART }}"
      echo "!VARF=${{ ! env.VARF }}"
      echo "!!VART=${{ !! env.VART }}"

The output is as follows:

VART=false
VART=true
VARF && VART=true
VARF || VART=false
!VARF=false
!!VART=true

The plain output is as expected, showing true and false. The output of the && and || operators is the opposite of expected, giving false && true == true and false || true == false. The output of ${{ ! env.VARF }} is false when I’d expect true.

What’s going on here? Possibly variables in the env context get coerced to strings, but that still doesn’t explain all the results.