Enable R8/ProGuard for Android releases and upload mapping to Google Play

Agent-Logs-Url: https://github.com/richardthe3rd/cambridge-beer-festival-app/sessions/973c3cd3-1aef-488c-9251-0615981b4ff2

Co-authored-by: richardthe3rd <573334+richardthe3rd@users.noreply.github.com>

Author: Copilot

.github/workflows/release-android.yml

@@ -145,6 +145,15 @@ jobs:
           if-no-files-found: error
           retention-days: 7
 
+      - name: Upload mapping file (deobfuscation)
+        if: matrix.build-type.name == 'appbundle'
+        uses: actions/upload-artifact@v4
+        with:
+          name: android-mapping
+          path: build/app/outputs/mapping/release/mapping.txt
+          if-no-files-found: error
+          retention-days: 7
+
   # Create release with all artifacts
   create-release:
     needs: [version-info, build-artifacts]
@@ -237,11 +246,18 @@ jobs:
           name: android-aab
           path: artifacts/aab
 
+      - name: Download mapping file artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: android-mapping
+          path: artifacts/mapping
+
       - name: Upload to Google Play (Internal track)
         uses: r0adkll/upload-google-play@v1
         with:
           serviceAccountJsonPlainText: ${{ secrets.GOOGLE_PLAY_SERVICE_ACCOUNT_JSON }}
           packageName: ralcock.cbf
           releaseFiles: artifacts/aab/app-release.aab
+          mappingFile: artifacts/mapping/mapping.txt
           track: internal
           status: completed

android/app/build.gradle

@@ -48,8 +48,9 @@ android {
         release {
             // Uses upload keystore when key.properties exists (CI), debug signing otherwise (local dev)
             signingConfig = keystorePropertiesFile.exists() ? signingConfigs.release : signingConfigs.debug
-            minifyEnabled = false
-            shrinkResources = false
+            minifyEnabled = true
+            shrinkResources = true
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
         }
     }
 }

android/app/proguard-rules.pro

@@ -0,0 +1,26 @@
+# Flutter wrapper classes (wildcard covers all io.flutter.** subpackages)
+-keep class io.flutter.** { *; }
+
+# Preserve Flutter plugin registrant (auto-generated)
+-keep class io.flutter.plugins.GeneratedPluginRegistrant { *; }
+
+# Keep native methods
+-keepclassmembers class * {
+    native <methods>;
+}
+
+# Keep annotations used by Flutter plugins
+-keepattributes Signature
+-keepattributes *Annotation*
+-keepattributes InnerClasses
+-keepattributes EnclosingMethod
+
+# Firebase SDKs bundle their own consumer ProGuard rules, but suppress missing-class
+# warnings for GMS classes that may be referenced but not included in all variants.
+-dontwarn com.google.android.gms.**
+
+# Suppress warnings about missing optional classes
+-dontwarn androidx.lifecycle.**
+-dontwarn org.conscrypt.**
+-dontwarn org.bouncycastle.**
+-dontwarn org.openjsse.**

docs/tooling/android-release.md

@@ -691,10 +691,7 @@ storeFile=../../upload-keystore.jks
 
 ## Code Obfuscation & Optimization (ProGuard/R8)
 
-Currently, ProGuard/R8 is **disabled** (`minifyEnabled = false`). This is intentional for initial releases to:
-- Simplify debugging
-- Avoid potential obfuscation issues with Flutter/Dart
-- Reduce initial build complexity
+Currently, ProGuard/R8 is **enabled** (`minifyEnabled = true`). This reduces app size and generates a deobfuscation mapping file that is automatically uploaded to Google Play Console, making crash analysis easier.
 
 ### Why Enable ProGuard/R8?
 
@@ -791,20 +788,20 @@ retrace.sh -verbose mapping.txt obfuscated_trace.txt
 
 ### Recommendation for This App
 
-**Current Status**: ✅ ProGuard/R8 disabled for simplicity
+**Current Status**: ✅ ProGuard/R8 enabled
 
-**Recommended Approach**:
-1. **Initial releases**: Keep disabled (current setup)
-2. **After stability**: Enable on a beta track first
-3. **Test thoroughly**: Ensure all features work (especially URL launching, storage)
-4. **Monitor**: Watch for crashes in Play Console
-5. **Rollout**: Move to production if stable
+The mapping file is automatically uploaded to Google Play Console as part of the CI release workflow,
+enabling automatic deobfuscation of crash stack traces in the Play Console.
 
-**When to Enable**:
-- App is stable in production
-- You want to reduce APK size (currently ~20-25 MB)
-- You're concerned about code security
-- You have time to debug potential issues
+**If you need to deobfuscate a stack trace locally:**
+
+```bash
+# Mapping file location (after a release build)
+build/app/outputs/mapping/release/mapping.txt
+
+# Use retrace to deobfuscate a crash trace:
+java -jar /path/to/retrace.jar mapping.txt obfuscated_trace.txt
+```
 
 ## Testing Before Release