Switch testing strategy on Github Actions to one based on a dynamic matrix

Currently the output is unreadable (I have no idea without digging _what_ test failed).

.github/generate-matrix.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+import subprocess
+import json
+import sys
+
+
+expr = 'builtins.toJSON (builtins.attrNames (import ./tests {}))'
+
+
+if __name__ == '__main__':
+    attrs = json.loads(json.loads(subprocess.check_output([
+        "nix-instantiate",
+        "--eval",
+        "--expr",
+        expr
+    ])))
+
+    matrix = [
+        {
+            "attr": attr
+        }
+        for attr in attrs
+    ]
+
+    sys.stdout.write("::set-output name=matrix::")
+    json.dump({"include": matrix}, sys.stdout)
+    sys.stdout.flush()

.github/workflows/ci.yml

@@ -2,9 +2,6 @@ name: CI
 
 on:
   pull_request:
-  push:
-    paths-ignore:
-    - '**.md'
 
 jobs:
   nixpkgs-fmt:
@@ -18,20 +15,32 @@ jobs:
     - name: Check format
       run: ./check-fmt
 
-  build:
+  matrix_generate:
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
-    strategy:
+    outputs:
-      matrix:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
-        os: [ubuntu-latest]
-        # os: [ubuntu-latest, macos-latest]
     steps:
-    - uses: cachix/install-nix-action@v14
+      - uses: actions/checkout@v2.4.0
-      with:
+      - uses: cachix/install-nix-action@v14
-        nix_path: nixpkgs=channel:nixos-unstable
+        with:
-        extra_nix_config: experimental-features = nix-command
+          nix_path: nixpkgs=channel:nixos-unstable
-    - uses: actions/checkout@v2.4.0
+          extra_nix_config: experimental-features = nix-command
-    - uses: cachix/cachix-action@v10
+      - id: set-matrix
-      with:
+        run: ./.github/generate-matrix.py
-        name: poetry2nix
+
-        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
+  builds:
-    - run: nix-shell -p nix-build-uncached --run 'nix-build-uncached --keep-going --show-trace tests/default.nix'
+    needs: matrix_generate
+    runs-on: ubuntu-latest
+    strategy:
+      matrix: ${{fromJSON(needs.matrix_generate.outputs.matrix)}}
+    steps:
+      - uses: actions/checkout@v2.4.0
+      - uses: cachix/install-nix-action@v14
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+          extra_nix_config: experimental-features = nix-command
+      - uses: cachix/cachix-action@v10
+        with:
+          name: poetry2nix
+          signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
+      - run: nix-shell -p nix-build-uncached --run 'nix-build-uncached --keep-going --show-trace tests/default.nix -A ${{ matrix.attr }}'