Improve expected failures and use them on Windows as well (#9)

.github/actions/expected-failure/action.yml

@@ -0,0 +1,39 @@
+---
+
+inputs:
+  step-outcome:
+    description: 'Outcome of the step to consider'
+  expected-failure:
+    description: 'Whether a failure is expected'
+
+runs:
+  using: composite
+
+  steps:
+    - if: ${{ inputs.step-outcome == 'success'
+              && inputs.expected-failure != 'expected-failure' }}
+      shell: bash
+      run: |
+        echo "The step succeeded and was planned to succeed."
+        exit 0
+
+    - if: ${{ inputs.step-outcome != 'success'
+              && inputs.expected-failure == 'expected-failure' }}
+      shell: bash
+      run: |
+        echo "The step failed and was planned to fail."
+        exit 0
+
+    - if: ${{ inputs.step-outcome == 'success'
+              && inputs.expected-failure == 'expected-failure' }}
+      shell: bash
+      run: |
+        echo "The step succeeded but was planned to fail."
+        exit 1
+
+    - if: ${{ inputs.step-outcome != 'success'
+              && inputs.expected-failure != 'expected-failure' }}
+      shell: bash
+      run: |
+        echo "The step failed but was planned to succeed."
+        exit 1

.github/workflows/ci.yml

@@ -56,10 +56,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os:
-          - ubuntu
-          - windows
-          - macos
+        include:
+          - {os: ubuntu}
+          - {os: windows, ef: expected-failure}
+          - {os: macos}
 
     runs-on: ${{ matrix.os }}-latest
 
@@ -77,6 +77,11 @@ jobs:
           opam-depext: true  ## this is the default; set here explicitly
 
       - name: Install Topiary
+        id: install-topiary
+        ## `continue-on-error` will make this step succeed no matter what. The
+        ## next step will then handle the outcome of this step manually. This is
+        ## what allows us to emulate an expected CI failure.
+        continue-on-error: true
         run: |
           ## Install Topiary then report where it is and in which version.
           echo '::group::Install Topiary'
@@ -89,7 +94,14 @@ jobs:
           opam exec -- topiary --version
           echo '::endgroup::'
 
+      - name: Check the outcome of the build
+        uses: ./.github/actions/expected-failure
+        with:
+          step-outcome: ${{ steps.install-topiary.outcome }}
+          expected-failure: ${{ matrix.ef }}
+
       - name: Run a smoke test
+        if: steps.install-topiary.outcome == 'success'
         run: |
           ## Run a tiny smoke test; checking that Topiary manages to start,
           ## parse a simple OCaml command and output the right thing.
@@ -101,6 +113,7 @@ jobs:
       ## Topiary v0.1.0. These should be re-enabled in future versions.
 
       # - name: Run tests
+      #   if: steps.install-topiary.outcome == 'success'
       #   run: |
       #     ## Test on OCaml implementation files (.ml)
       #     cat topiary/tests/samples/input/ocaml.ml | opam exec -- topiary --language ocaml-implementation > ocaml.ml
@@ -134,10 +147,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v3
 
-      - name: Build Docker image (see next steps for failure)
+      - name: Build Docker image (see next step for failure)
         id: build-docker-image
-        ## `continue-on-error` will make this step succeed no matter what. Later
-        ## steps will then handle the outcome of this step manually. This is
+        ## `continue-on-error` will make this step succeed no matter what. The
+        ## next step will then handle the outcome of this step manually. This is
         ## what allows us to emulate an expected CI failure.
         continue-on-error: true
         run: |
@@ -147,22 +160,11 @@ jobs:
             --file .github/workflows/ci.dockerfile \
             --build-arg tag=${{matrix.tag}}
 
-      - name: Building the image succeeded and was planned to succeed
-        if: ${{ steps.build-docker-image.outcome == 'success'
-                && matrix.ef != 'expected-failure' }}
-        run: "true"
-      - name: Building the image failed and was planned to fail
-        if: ${{ steps.build-docker-image.outcome != 'success'
-                && matrix.ef == 'expected-failure' }}
-        run: "true"
-      - name: Building the image succeeded but was planned to fail
-        if: ${{ steps.build-docker-image.outcome == 'success'
-                && matrix.ef == 'expected-failure' }}
-        run: "false"
-      - name: Building the image failed but was planned to succeed
-        if: ${{ steps.build-docker-image.outcome == 'failure'
-                && matrix.ef != 'expected-failure' }}
-        run: "false"
+      - name: Check the outcome of the build
+        uses: ./.github/actions/expected-failure
+        with:
+          step-outcome: ${{ steps.build-docker-image.outcome }}
+          expected-failure: ${{ matrix.ef }}
 
       - name: Run a tiny smoke test
         if: steps.build-docker-image.outcome == 'success'