Apply latest Github Actions best practices for Elixir projects

.github/workflows/ci.yml

@@ -1,73 +1,67 @@
 name: CI
 
 on:
-  push:
-    branches: [ master ]
   pull_request:
-    branches: [ master ]
+  push:
+    branches:
+      - master
 
 jobs:
-  format:
-    name: Check Formatting
-    runs-on: ubuntu-16.04
-    steps:
-      - uses: actions/checkout@v2
-
-      - name: Set up Elixir
-        uses: erlef/setup-elixir@v1
-        with:
-          otp-version: 22.2
-          elixir-version: 1.10.4
-
-      - name: Install dependencies
-        run: mix deps.get
-
-      - name: Run "mix format"
-        run: mix format --check-formatted
-
   test:
-    name: Build and test
     runs-on: ubuntu-16.04
+    env:
+      MIX_ENV: test
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     strategy:
       fail-fast: false
       matrix:
-        pair:
-          - erlang: 23.1
-            elixir: 1.11.1
-          - erlang: 22.2
-            elixir: 1.11.1
-          - erlang: 21.3
-            elixir: 1.11.1
-          - erlang: 22.2
-            elixir: 1.10.4
-          - erlang: 20.3.1
-            elixir: 1.9.4
-    env:
-      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        include:
+          - pair:
+              elixir: 1.9.4
+              otp: 20.3.1
+          - pair:
+              elixir: 1.11.1
+              otp: 21.3
+          - pair:
+              elixir: 1.10.4
+              otp: 22.2
+          - pair:
+              elixir: 1.11.3
+              otp: 22.2
+          - pair:
+              elixir: 1.11.3
+              otp: 23.2.5
+            lint: lint
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up Elixir
-        uses: erlef/setup-elixir@v1
+      - uses: erlef/setup-elixir@v1
         with:
-          otp-version: ${{matrix.pair.erlang}}
+          otp-version: ${{matrix.pair.otp}}
           elixir-version: ${{matrix.pair.elixir}}
 
-      - name: Install dependencies
-        run: |
-          mix local.hex --force
-          mix local.rebar --force
-          mix deps.get
+      - name: Install Dependencies
+        run: mix deps.get --only test
 
-      - name: Run tests
-        run: MIX_ENV=test mix coveralls.github
+      - run: mix format --check-formatted
+        if: ${{ matrix.lint }}
+
+      - run: mix deps.get && mix deps.unlock --check-unused
+        if: ${{ matrix.lint }}
+
+      - run: mix deps.compile
+
+      - run: mix compile --warnings-as-errors
+        if: ${{ matrix.lint }}
+
+      - run: mix test coveralls.github
 
       - name: Retrieve PLT Cache
         uses: actions/cache@v1
         id: plt-cache
         with:
           path: priv/plts
-          key: ${{ runner.os }}-${{ matrix.pair.erlang }}-${{ matrix.pair.elixir }}-plts-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
+          key: ${{ runner.os }}-${{ matrix.pair.otp }}-${{ matrix.pair.elixir }}-plts-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
 
       - name: Create PLTs
         if: steps.plt-cache.outputs.cache-hit != 'true'
@@ -76,4 +70,4 @@ jobs:
           mix dialyzer --plt
 
       - name: Run dialyzer
-        run: mix dialyzer --no-check
+        run: mix dialyzer --no-check --halt-exit-status