flutter335: fix android build

This patch introduces an intermediate Gradle build step to alter the behavior

of flutter_tools' Gradle project, specifically moving the creation of `build`

and `.gradle` directories from within the Nix Store to somewhere in `$HOME/.cache/flutter/nix-flutter-tools-gradle/$engineShortRev`.

Without this patch, flutter_tools' Gradle project tries to generate `build` and `.gradle`

directories within the Nix Store. Resulting in read-only errors when trying to build a

Flutter Android app at runtime.

This patch takes advantage of the fact settings.gradle takes priority over settings.gradle.kts to build the intermediate Gradle project

when a Flutter app runs `includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")`

`rootProject.buildFileName = "/dev/null"` so that the intermediate project doesn't use `build.gradle.kts` that's in the same directory.

The intermediate project makes a `settings.gradle` file in `$HOME/.cache/flutter/nix-flutter-tools-gradle/<short engine rev>/` and `includeBuild`s it.

This Gradle project will build the actual `packages/flutter_tools/gradle` project by setting

`rootProject.projectDir = new File("$settingsDir")` and `apply from: new File("$settingsDir/settings.gradle.kts")`.

To move `build` to `$HOME/.cache/flutter/nix-flutter-tools-gradle/<short engine rev>/`, we need to set `buildDirectory`.

To move `.gradle` as well, the `--project-cache-dir` argument must be passed to the Gradle wrapper.

Changing the `GradleUtils.getExecutable` function signature is a delibarate choice, to ensure that no new unpatched usages slip in.

--- /dev/null

+++ b/packages/flutter_tools/gradle/settings.gradle

@@ -0,0 +1,19 @@

+rootProject.buildFileName = "/dev/null"

+

+def engineShortRev = (new File("$settingsDir/../../../bin/internal/engine.version")).text.take(10)

+def dir = new File("$System.env.HOME/.cache/flutter/nix-flutter-tools-gradle/$engineShortRev")

+dir.mkdirs()

+def file = new File(dir, "settings.gradle")

+

+file.text = """

+rootProject.projectDir = new File("$settingsDir")

+apply from: new File("$settingsDir/settings.gradle.kts")

+

+gradle.allprojects { project ->

+  project.beforeEvaluate {

+    project.layout.buildDirectory = new File("$dir/build")

+  }

+}

+"""

+

+includeBuild(dir)

--- a/packages/flutter_tools/gradle/build.gradle.kts

+++ b/packages/flutter_tools/gradle/build.gradle.kts

@@ -4,6 +4,11 @@

 import org.jetbrains.kotlin.gradle.dsl.JvmTarget

+// While flutter_tools runs Gradle with a --project-cache-dir, this startParameter

+// is not passed correctly to the Kotlin Gradle plugin for some reason, and so

+// must be set here as well.

+gradle.startParameter.projectCacheDir = layout.buildDirectory.dir("cache").get().asFile

+

 plugins {

     `java-gradle-plugin`

     groovy

--- a/packages/flutter_tools/lib/src/android/gradle.dart

+++ b/packages/flutter_tools/lib/src/android/gradle.dart

@@ -474,9 +474,9 @@ class AndroidGradleBuilder implements AndroidBuilder {

     // from the local.properties file.

     updateLocalProperties(project: project, buildInfo: androidBuildInfo.buildInfo);

-    final options = <String>[];

-

-    final String gradleExecutablePath = _gradleUtils.getExecutable(project);

+    final [String gradleExecutablePath, ...List<String> options] = _gradleUtils.getExecutable(

+      project,

+    );

     // All automatically created files should exist.

     if (configOnly) {

@@ -797,7 +797,7 @@ class AndroidGradleBuilder implements AndroidBuilder {

       'aar_init_script.gradle',

     );

     final command = <String>[

-      _gradleUtils.getExecutable(project),

+      ..._gradleUtils.getExecutable(project),

       '-I=$initScript',

       '-Pflutter-root=$flutterRoot',

       '-Poutput-dir=${outputDirectory.path}',

@@ -912,6 +912,10 @@ class AndroidGradleBuilder implements AndroidBuilder {

     final results = <String>[];

     try {

+      final [String gradleExecutablePath, ...List<String> options] = _gradleUtils.getExecutable(

+        project,

+      );

+

       exitCode = await _runGradleTask(

         _kBuildVariantTaskName,

         preRunTask: () {

@@ -927,10 +931,10 @@ class AndroidGradleBuilder implements AndroidBuilder {

             ),

           );

         },

-        options: const <String>['-q'],

+        options: <String>[...options, '-q'],

         project: project,

         localGradleErrors: gradleErrors,

-        gradleExecutablePath: _gradleUtils.getExecutable(project),

+        gradleExecutablePath: gradleExecutablePath,

         outputParser: (String line) {

           if (_kBuildVariantRegex.firstMatch(line) case final RegExpMatch match) {

             results.add(match.namedGroup(_kBuildVariantRegexGroupName)!);

@@ -964,6 +968,10 @@ class AndroidGradleBuilder implements AndroidBuilder {

     late Stopwatch sw;

     var exitCode = 1;

     try {

+      final [String gradleExecutablePath, ...List<String> options] = _gradleUtils.getExecutable(

+        project,

+      );

+

       exitCode = await _runGradleTask(

         taskName,

         preRunTask: () {

@@ -979,10 +987,10 @@ class AndroidGradleBuilder implements AndroidBuilder {

             ),

           );

         },

-        options: <String>['-q', '-PoutputPath=$outputPath'],

+        options: <String>[...options, '-q', '-PoutputPath=$outputPath'],

         project: project,

         localGradleErrors: gradleErrors,

-        gradleExecutablePath: _gradleUtils.getExecutable(project),

+        gradleExecutablePath: gradleExecutablePath,

       );

     } on Error catch (error) {

       _logger.printError(error.toString());

--- a/packages/flutter_tools/lib/src/android/gradle_errors.dart

+++ b/packages/flutter_tools/lib/src/android/gradle_errors.dart

@@ -228,7 +228,12 @@ final flavorUndefinedHandler = GradleHandledError(

   },

   handler: ({required String line, required FlutterProject project, required bool usesAndroidX}) async {

     final RunResult tasksRunResult = await globals.processUtils.run(

-      <String>[globals.gradleUtils!.getExecutable(project), 'app:tasks', '--all', '--console=auto'],

+      <String>[

+        ...globals.gradleUtils!.getExecutable(project),

+        'app:tasks',

+        '--all',

+        '--console=auto',

+      ],

       throwOnError: true,

       workingDirectory: project.android.hostAppGradleRoot.path,

       environment: globals.java?.environment,

--- a/packages/flutter_tools/lib/src/android/gradle_utils.dart

+++ b/packages/flutter_tools/lib/src/android/gradle_utils.dart

@@ -3,6 +3,7 @@

 // found in the LICENSE file.

 import 'package:meta/meta.dart';

+import 'package:path/path.dart';

 import 'package:process/process.dart';

 import 'package:unified_analytics/unified_analytics.dart';

@@ -197,9 +198,29 @@ class GradleUtils {

   final Logger _logger;

   final OperatingSystemUtils _operatingSystemUtils;

+  List<String> get _requiredArguments {

+    final String cacheDir = join(

+      switch (globals.platform.environment['XDG_CACHE_HOME']) {

+        final String cacheHome => cacheHome,

+        _ => join(

+          globals.fsUtils.homeDirPath ?? throwToolExit('No cache directory has been specified.'),

+          '.cache',

+        ),

+      },

+      'flutter',

+      'nix-flutter-tools-gradle',

+      globals.flutterVersion.engineRevision.substring(0, 10),

+    );

+

+    return <String>[

+      '--project-cache-dir=${join(cacheDir, 'cache')}',

+      '-Pkotlin.project.persistent.dir=${join(cacheDir, 'kotlin')}',

+    ];

+  }

+

   /// Gets the Gradle executable path and prepares the Gradle project.

   /// This is the `gradlew` or `gradlew.bat` script in the `android/` directory.

-  String getExecutable(FlutterProject project) {

+  List<String> getExecutable(FlutterProject project) {

     final Directory androidDir = project.android.hostAppGradleRoot;

     injectGradleWrapperIfNeeded(androidDir);

@@ -210,7 +231,7 @@ class GradleUtils {

       // If the Gradle executable doesn't have execute permission,

       // then attempt to set it.

       _operatingSystemUtils.makeExecutable(gradle);

-      return gradle.absolute.path;

+      return <String>[gradle.absolute.path, ..._requiredArguments];

     }

     throwToolExit(

       'Unable to locate gradlew script. Please check that ${gradle.path} '

--- a/packages/flutter_tools/test/general.shard/android/android_gradle_builder_test.dart

+++ b/packages/flutter_tools/test/general.shard/android/android_gradle_builder_test.dart

@@ -2606,8 +2606,8 @@ Gradle Crashed

 class FakeGradleUtils extends Fake implements GradleUtils {

   @override

-  String getExecutable(FlutterProject project) {

-    return 'gradlew';

+  List<String> getExecutable(FlutterProject project) {

+    return const <String>['gradlew'];

   }

 }

--- a/packages/flutter_tools/test/general.shard/android/gradle_errors_test.dart

+++ b/packages/flutter_tools/test/general.shard/android/gradle_errors_test.dart

@@ -1633,8 +1633,8 @@ Platform fakePlatform(String name) {

 class FakeGradleUtils extends Fake implements GradleUtils {

   @override

-  String getExecutable(FlutterProject project) {

-    return 'gradlew';

+  List<String> getExecutable(FlutterProject project) {

+    return const <String>['gradlew'];

   }

 }