Add CI workflow to check example sketches for compliance with the code formatting style

The existing examples_formatter.conf configuration for Artistic Style is used. Although this configuration does add some additional formatting rules, it will most often be possible to achieve compliance simply by using the IDE's Auto Format feature. The repository also contains an examples_formatter.sh script that will automatically format the examples according to the configuration.

Author: per1234

.github/workflows/code-formatting-check.yml

@@ -0,0 +1,63 @@
+name: Code Formatting Check
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/code-formatting-check.yml"
+      - "examples/**"
+  push:
+    paths:
+      - ".github/workflows/code-formatting-check.yml"
+      - "examples/**"
+
+jobs:
+  check-formatting:
+    runs-on: ubuntu-latest
+
+    env:
+      # See: https://sourceforge.net/projects/astyle/files/astyle/
+      ASTYLE_VERSION: 3.1
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      # See: http://astyle.sourceforge.net/
+      - name: Download Artistic Style
+        uses: carlosperate/download-file-action@v1.0.3
+        with:
+          file-url: https://iweb.dl.sourceforge.net/project/astyle/astyle/astyle%20${{ env.ASTYLE_VERSION }}/astyle_${{ env.ASTYLE_VERSION }}_linux.tar.gz
+          location: ${{ runner.temp }}/astyle
+
+      # See: http://astyle.sourceforge.net/install.html#_GCC_Makefile
+      - name: Build Artistic Style
+        run: |
+          # Build Artistic Style
+          cd "${{ runner.temp }}/astyle"
+          tar --extract --file="astyle_${{ env.ASTYLE_VERSION }}_linux.tar.gz"
+          cd "astyle/build/gcc"
+          make
+
+      # GITHUB_WORKSPACE
+      - name: Check code formatting
+        run: |
+          # Check code formatting of example sketches
+          # Don't exit on first formatting check fail
+          set +e
+          # Set default exit status
+          EXIT_STATUS=0
+          while read -r filePath; do
+            # Check if it's a file (find matches on pruned folders)
+            if [[ -f "$filePath" ]]; then
+              if ! diff --strip-trailing-cr "$filePath" <("${{ runner.temp }}/astyle/astyle/build/gcc/bin/astyle" --options="${GITHUB_WORKSPACE}/examples_formatter.conf" --dry-run <"$filePath"); then
+                echo "ERROR: Non-compliant code formatting in $filePath"
+                EXIT_STATUS=1
+              fi
+            fi
+          done <<<"$(find "${GITHUB_WORKSPACE}/examples" -regextype posix-extended \( -regex '.*\.((ino)|(h)|(cpp)|(c))$' -and -type f \))"
+          if [[ "$EXIT_STATUS" != "0" ]]; then
+            echo "Please do an Auto Format on the sketches:"
+            echo "Arduino IDE: Tools > Auto Format"
+            echo "Arduino Web Editor: Ctrl + B"
+          fi
+          exit "$EXIT_STATUS"

README.adoc

@@ -1,6 +1,7 @@
 = Built-in Examples =
 
 image:https://github.com/arduino/arduino-examples/workflows/Compile%20Examples/badge.svg["Compile Examples Status", link="https://github.com/arduino/arduino-examples/actions?workflow=Compile+Examples"]
+image:https://github.com/arduino/arduino-examples/workflows/Code%20Formatting%20Check/badge.svg["Code Formatting Check Status", link="https://github.com/arduino/arduino-examples/actions?workflow=Code+Formatting+Check"]
 image:https://github.com/arduino/arduino-examples/workflows/Spell%20Check/badge.svg["Spell Check Status", link="https://github.com/arduino/arduino-examples/actions?workflow=Spell+Check"]
 
 These are the example Arduino sketches built in to the Arduino IDE.