Experiment with loading matrix values from a file

The goal here is to avoid duplication of e.g. which versions of GHC we
support.

This is an experiment at the moment.

Author: michaelpj

.github/workflows/bench.yml

@@ -46,8 +46,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ['8.10.7', '9.2.5']
-        os: [ubuntu-latest]
+        ghc:
+          - '8.10.7'
+          - '9.2.5'
+        os:
+          - ubuntu-latest
 
     # This code is fitted to the strategy: assumes Linux is used ... etc,
     # change of the strategy may require changing the bootstrapping/run code

.github/workflows/caching.yml

@@ -54,8 +54,13 @@ jobs:
   pre_job:
     runs-on: ubuntu-latest
     outputs:
+      ghcs: ${{ steps.ghcs.outputs.ghcs }}
       should_skip: ${{ steps.skip_check.outputs.should_skip }}
     steps:
+      # Need the repo checked out in order to read the file
+      - uses: actions/checkout@v3
+      - id: ghcs
+        run: echo "ghcs=$(cat ./.github/workflows/supported-ghc-versions.json)" >> $GITHUB_OUTPUT
       - id: skip_check
         uses: fkirc/skip-duplicate-actions@v5.3.0
         with:
@@ -80,17 +85,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # This list of GHC (including the "exclude" list) versions must match
-        # to the list of GHC versions specified in 'test.yml'
-        ghc: [ "9.4.4"
-             , "9.2.5"
-             , "9.0.2"
-             , "8.10.7"
-             ]
-        os: [ "ubuntu-latest"
-            , "macOS-latest"
-            , "windows-latest"
-            ]
+        ghc: ${{ fromJSON(needs.pre_job.outputs.ghcs) }}
+        os:
+          - ubuntu-latest
+          - macOS-latest
+          - windows-latest
     steps:
       - uses: actions/checkout@v3
 

.github/workflows/flags.yml

@@ -18,8 +18,13 @@ jobs:
   pre_job:
     runs-on: ubuntu-latest
     outputs:
+      ghcs: ${{ steps.ghcs.outputs.ghcs }}
       should_skip: ${{ steps.skip_check.outputs.should_skip }}
     steps:
+      # Need the repo checked out in order to read the file
+      - uses: actions/checkout@v3
+      - id: ghcs
+        run: echo "ghcs=$(cat ./.github/workflows/supported-ghc-versions.json)" >> $GITHUB_OUTPUT
       - id: skip_check
         uses: fkirc/skip-duplicate-actions@v5.3.0
         with:
@@ -44,12 +49,9 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        ghc: [ "9.2.5"
-             , "9.0.2"
-             , "8.10.7"
-             ]
-        os: [ "ubuntu-latest"
-            ]
+        ghc: ${{ fromJSON(needs.pre_job.outputs.ghcs) }}
+        os:
+          - ubuntu-latest
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/supported-ghc-versions.json

@@ -0,0 +1 @@
+[ "9.4.4" , "9.2.5" , "9.0.2" , "8.10.7" ]

.github/workflows/test.yml

@@ -20,7 +20,12 @@ jobs:
     outputs:
       should_skip: ${{ steps.skip_check.outputs.should_skip }}
       should_skip_ghcide: ${{ steps.skip_ghcide_check.outputs.should_skip }}
+      ghcs: ${{ steps.ghcs.outputs.ghcs }}
     steps:
+      # Need the repo checked out in order to read the file
+      - uses: actions/checkout@v3
+      - id: ghcs
+        run: echo "ghcs=$(cat ./.github/workflows/supported-ghc-versions.json)" >> $GITHUB_OUTPUT
       - id: skip_check
         uses: fkirc/skip-duplicate-actions@v5.3.0
         with:
@@ -52,49 +57,26 @@ jobs:
 
   test:
     if: needs.pre_job.outputs.should_skip != 'true'
-    needs: pre_job
+    needs:
+      - pre_job
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: true
       # when you edit this list of GHC versions,
       # **don't forget**
       # to update the ghc versions in 'caching.yml'.
       matrix:
-        ghc: [ "9.4.4"
-             , "9.2.5"
-             , "9.0.2"
-             , "8.10.7"
-             ]
-        os: [ "ubuntu-latest"
-            , "macOS-latest"
-            , "windows-latest"
-            ]
-        # Mark which GHC versions on which platform we want to test.
+        ghc: ${{ fromJSON(needs.pre_job.outputs.ghcs) }}
+        os:
+          - ubuntu-latest
+          - macOS-latest
+          - windows-latest
+        # Mark which GHC versions on which platforms we want to test.
         include:
-           # only test supported ghc major versions
-           - os: ubuntu-latest
-             ghc: '9.4.4'
-             test: true
-           - os: ubuntu-latest
-             ghc: '9.2.5'
-             test: true
-           - os: ubuntu-latest
-             ghc: '9.0.2'
-             test: true
+           # Test all supported versions, but only on ubuntu and windows
            - os: ubuntu-latest
-             ghc: '8.10.7'
-             test: true
-           - os: windows-latest
-             ghc: '9.4.4'
-             test: true
-           - os: windows-latest
-             ghc: '9.2.5'
-             test: true
-           - os: windows-latest
-             ghc: '9.0.2'
              test: true
            - os: windows-latest
-             ghc: '8.10.7'
              test: true
 
     steps: