chore: implement selective builds on GitHub Actions (#185)

Author: thatfiredev

.github/workflows/android.yml

@@ -13,9 +13,13 @@ jobs:
       uses: actions/setup-java@v1
       with:
         java-version: 1.8
-    - name: Install NDK
-      run: echo "y" | sudo ${ANDROID_HOME}/tools/bin/sdkmanager --install "ndk;20.0.5594570" --sdk_root=${ANDROID_SDK_ROOT}
     - name: Check Snippets
       run: python scripts/checksnippets.py
-    - name: Build with Gradle
+    - name: Install NDK
+      run: echo "y" | sudo ${ANDROID_HOME}/tools/bin/sdkmanager --install "ndk;20.0.5594570" --sdk_root=${ANDROID_SDK_ROOT}
+    - name: Build with Gradle (Pull Request)
+      run: ./build_pull_request.sh
+      if: github.event_name == 'pull_request'
+    - name: Build with Gradle (Push)
       run: ./gradlew clean ktlint build
+      if: github.event_name != 'pull_request'

build_pull_request.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+# Exit on error
+set -e
+
+# unshallow since GitHub actions does a shallow clone
+git fetch --unshallow
+git fetch origin
+
+# Get all the modules that were changed
+while read line; do
+  module_name=${line%%/*}
+  if [[ ${MODULES} != *"${module_name}"* ]]; then
+    MODULES="${MODULES} ${module_name}"
+  fi
+done < <(git diff --name-only origin/$GITHUB_BASE_REF)
+changed_modules=$MODULES
+
+# Get a list of all available gradle tasks
+AVAILABLE_TASKS=$(./gradlew tasks --all)
+
+# Check if these modules have gradle tasks
+build_commands=""
+for module in $changed_modules
+do
+  if [[ $AVAILABLE_TASKS =~ $module":app:" ]]; then
+    build_commands=${build_commands}" :"${module}":app:assembleDebug :"${module}":app:check"
+  fi
+done
+
+# Build
+echo "Building Pull Request with"
+echo $build_commands
+eval "./gradlew clean ktlint ${build_commands}"