[multi-package]Fix packages issue builtinkotlin AGP 9

[daniJimen]

Fixes flutter/flutter#186795

Pre-Review Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools.
• I read the [Tree Hygiene] page, which explains my responsibilities.
• I read and followed the [relevant style guides] and ran [the auto-formatter].
• I signed the [CLA].
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I [linked to at least one issue that this PR fixes] in the description above.
• I followed [the version and CHANGELOG instructions], using [semantic versioning] and the [repository CHANGELOG style], or I have commented below to indicate which documented exception this PR falls under[^1].
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which [test exemption] this PR falls under[^1].
• All existing and new tests are passing.

Explanation:

Updates build.gradle.kts files across multiple Flutter plugin examples and Android library modules to conditionally apply the Kotlin Android plugin. AGP 9.0 introduces built-in Kotlin support, making explicit application of the kotlin-android plugin redundant unless specifically disabled.

Changes

• Conditional Plugin Application: Removed the static id("kotlin-android") and added logic to check the ANDROID_GRADLE_PLUGIN_VERSION. The org.jetbrains.kotlin.android plugin is now applied programmatically only if the AGP version is below 9 or if the android.builtInKotlin Gradle property is set to false.
• Safe Kotlin Configuration: Wrapped kotlinOptions in a conditional block. When built-in Kotlin is active (AGP 9+), the explicit kotlinOptions block is skipped. When inactive, it uses withGroovyBuilder to set jvmTarget to VERSION_17, ensuring compatibility without causing build script evaluation errors when the plugin is absent.
• Broad Impact: Applied these changes across a wide range of packages, including camera, google_maps_flutter, image_picker, video_player, webview_flutter, shared_preferences, and pigeon.

Test plan

These changes ensure that plugin examples and libraries remain compatible across a range of AGP versions, specifically handling the transition to built-in Kotlin support in AGP 9.0 while maintaining backward compatibility for older environments.

based into: #11692

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[daniJimen]

Fixes flutter/flutter#186795

Pre-Review Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools.
• I read the [Tree Hygiene] page, which explains my responsibilities.
• I read and followed the [relevant style guides] and ran [the auto-formatter].
• I signed the [CLA].
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I [linked to at least one issue that this PR fixes] in the description above.
• I followed [the version and CHANGELOG instructions], using [semantic versioning] and the [repository CHANGELOG style], or I have commented below to indicate which documented exception this PR falls under[^1].
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which [test exemption] this PR falls under[^1].
• All existing and new tests are passing.

Explanation:

Updates build.gradle.kts files across multiple Flutter plugin examples and Android library modules to conditionally apply the Kotlin Android plugin. AGP 9.0 introduces built-in Kotlin support, making explicit application of the kotlin-android plugin redundant unless specifically disabled.

Changes

• Conditional Plugin Application: Removed the static id("kotlin-android") and added logic to check the ANDROID_GRADLE_PLUGIN_VERSION. The org.jetbrains.kotlin.android plugin is now applied programmatically only if the AGP version is below 9 or if the android.builtInKotlin Gradle property is set to false.
• Safe Kotlin Configuration: Wrapped kotlinOptions in a conditional block. When built-in Kotlin is active (AGP 9+), the explicit kotlinOptions block is skipped. When inactive, it uses withGroovyBuilder to set jvmTarget to VERSION_17, ensuring compatibility without causing build script evaluation errors when the plugin is absent.
• Broad Impact: Applied these changes across a wide range of packages, including camera, google_maps_flutter, image_picker, video_player, webview_flutter, shared_preferences, and pigeon.

Test plan

These changes ensure that plugin examples and libraries remain compatible across a range of AGP versions, specifically handling the transition to built-in Kotlin support in AGP 9.0 while maintaining backward compatibility for older environments.

based into: #11692

I propose adding a CI workflow that verifies every Android-capable package in the repository builds successfully with both Android Gradle Plugin (AGP) 8.x and 9.x like:

name: Android AGP compatibility

on:
  push:
    branches: [master, main]
  pull_request:
    branches: [master, main]
  workflow_dispatch:

permissions:
  contents: read

jobs:
  discover-examples:
    runs-on: ubuntu-latest
    outputs:
      examples: ${{ steps.find.outputs.examples }}
    steps:
      - uses: actions/checkout@v6

      - name: Discover Android examples
        id: find
        run: |
          # Find all example/android/settings.gradle.kts across packages/ and third_party/packages/
          examples=$(find packages third_party/packages -path "*/example/android/settings.gradle.kts" \
            -not -path "*/build/*" \
            2>/dev/null \
            | sed 's|/android/settings.gradle.kts||' \
            | sort \
            | jq -R -s -c 'split("\n") | map(select(length > 0))')
          echo "examples=$examples" >> "$GITHUB_OUTPUT"
          echo "Found examples:"
          echo "$examples" | jq .

  android-agp-matrix:
    needs: discover-examples
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        example: ${{ fromJson(needs.discover-examples.outputs.examples) }}
        agp:
          - lane: agp-8.x
            agp_version: "8.9.1"
            gradle_version: "8.14.3"
            kotlin_version: "2.2.20"
            built_in_kotlin: ""
          - lane: agp-9.x
            agp_version: "9.2.1"
            gradle_version: "9.5.0"
            kotlin_version: "2.3.21"
            built_in_kotlin: "false"

    name: "${{ matrix.example }} — ${{ matrix.agp.lane }}"

    steps:
      - uses: actions/checkout@v6

      - uses: actions/setup-java@v4
        with:
          distribution: temurin
          java-version: '17'

      - uses: subosito/flutter-action@v2
        with:
          flutter-version: 3.32.8
          cache: true

      - name: Show toolchain versions
        run: |
          flutter --version
          java -version

      - name: Patch Android config for ${{ matrix.agp.lane }}
        shell: bash
        env:
          AGP_VERSION: ${{ matrix.agp.agp_version }}
          GRADLE_VERSION: ${{ matrix.agp.gradle_version }}
          KOTLIN_VERSION: ${{ matrix.agp.kotlin_version }}
          BUILT_IN_KOTLIN: ${{ matrix.agp.built_in_kotlin }}
          EXAMPLE_DIR: ${{ matrix.example }}
        run: |
          python3 <<'PY'
          from pathlib import Path
          import os
          import re
          import sys

          agp_version = os.environ['AGP_VERSION']
          gradle_version = os.environ['GRADLE_VERSION']
          kotlin_version = os.environ['KOTLIN_VERSION']
          built_in_kotlin = os.environ['BUILT_IN_KOTLIN']

          example_dir = Path(os.environ['EXAMPLE_DIR'])

          def patch_settings(settings_file):
              """Patch AGP and Kotlin versions in a settings.gradle.kts file."""
              if not settings_file.exists():
                  return

              settings = settings_file.read_text()

              # Patch AGP (com.android.application or com.android.library)
              settings, n = re.subn(
                  r'id\("com\.android\.(application|library)"\) version "[^"]+" apply false',
                  lambda m: f'id("com.android.{m.group(1)}") version "{agp_version}" apply false',
                  settings,
              )
              if n == 0:
                  print(f"⚠️  No AGP plugin found in {settings_file}, skipping AGP patch.")

              # Patch Kotlin version
              settings, n = re.subn(
                  r'id\("org\.jetbrains\.kotlin\.android"\) version "[^"]+" apply false',
                  f'id("org.jetbrains.kotlin.android") version "{kotlin_version}" apply false',
                  settings,
              )
              if n == 0:
                  print(f"⚠️  No Kotlin plugin found in {settings_file}, skipping Kotlin patch.")

              settings_file.write_text(settings)
              print(f"✅ Patched {settings_file}")

          def patch_wrapper(wrapper_file):
              """Patch Gradle distribution version."""
              if not wrapper_file.exists():
                  return
              wrapper = wrapper_file.read_text()
              wrapper, n = re.subn(
                  r'gradle-[^-]+-all\.zip',
                  f'gradle-{gradle_version}-all.zip',
                  wrapper, count=1,
              )
              if n != 1:
                  print(f"⚠️  Could not patch Gradle wrapper in {wrapper_file}")
                  sys.exit(1)
              wrapper_file.write_text(wrapper)
              print(f"✅ Patched {wrapper_file}")

          def patch_gradle_properties(props_file):
              """Patch builtInKotlin flag."""
              if not props_file.exists():
                  return
              filtered_lines = []
              for line in props_file.read_text().splitlines():
                  if line.startswith('android.builtInKotlin='):
                      continue
                  if line.strip() == '# This builtInKotlin flag was added automatically by Flutter migrator':
                      continue
                  filtered_lines.append(line)
              if built_in_kotlin:
                  filtered_lines.append(f'android.builtInKotlin={built_in_kotlin}')
              props_file.write_text('\n'.join(filtered_lines) + '\n')
              print(f"✅ Patched {props_file}")

          # 1. Patch the example's android/ directory
          example_android = example_dir / 'android'
          if not (example_android / 'settings.gradle.kts').exists():
              print(f"⚠️  {example_android / 'settings.gradle.kts'} not found, skipping.")
              sys.exit(0)

          patch_settings(example_android / 'settings.gradle.kts')
          patch_wrapper(example_android / 'gradle' / 'wrapper' / 'gradle-wrapper.properties')
          patch_gradle_properties(example_android / 'gradle.properties')

          # 2. Patch the parent package's android/ directory (plugin library project)
          #    The package root is the parent of the example/ directory.
          package_android = example_dir.parent / 'android'
          if (package_android / 'settings.gradle.kts').exists():
              print(f"📦 Also patching plugin package at {package_android}")
              patch_settings(package_android / 'settings.gradle.kts')
              patch_wrapper(package_android / 'gradle' / 'wrapper' / 'gradle-wrapper.properties')
              patch_gradle_properties(package_android / 'gradle.properties')

          print("🎉 All patching complete.")
          PY

      - name: Show Android diff
        run: |
          # Show diff for the example's android dir
          git --no-pager diff -- "${{ matrix.example }}/android" | cat
          # Show diff for the parent package's android dir (if it exists)
          PACKAGE_ANDROID="$(dirname "${{ matrix.example }}")/android"
          if [ -d "$PACKAGE_ANDROID" ]; then
            git --no-pager diff -- "$PACKAGE_ANDROID" | cat
          fi

      - name: Install dependencies
        working-directory: ${{ matrix.example }}
        run: flutter pub get

      - name: Build Android APK (debug)
        working-directory: ${{ matrix.example }}
        run: flutter build apk --debug

What do you think? I appreciate your opinion. @reidbaker @jesswrd