[flutter_tools] temporary directory (#105815)

packages/flutter_tools/lib/src/base/file_system.dart

@@ -6,6 +6,7 @@ import 'package:file/file.dart';
 import 'package:file/local.dart' as local_fs;
 import 'package:meta/meta.dart';
 
+import 'common.dart';
 import 'io.dart';
 import 'platform.dart';
 import 'process.dart';
@@ -218,7 +219,12 @@ class LocalFileSystem extends local_fs.LocalFileSystem {
   @override
   Directory get systemTempDirectory {
     if (_systemTemp == null) {
-      _systemTemp = super.systemTempDirectory.createTempSync('flutter_tools.')
+      if (!superSystemTempDirectory.existsSync()) {
+        throwToolExit('Your system temp directory (${superSystemTempDirectory.path}) does not exist. '
+          'Did you set an invalid override in your environment? See issue https://github.com/flutter/flutter/issues/74042 for more context.'
+        );
+      }
+      _systemTemp = superSystemTempDirectory.createTempSync('flutter_tools.')
         ..createSync(recursive: true);
       // Make sure that the temporary directory is cleaned up if the tool is
       // killed by a signal.
@@ -239,4 +245,8 @@ class LocalFileSystem extends local_fs.LocalFileSystem {
     }
     return _systemTemp!;
   }
+
+  // This only exist because the memory file system does not support a systemTemp that does not exists #74042
+  @visibleForTesting
+  Directory get superSystemTempDirectory => super.systemTempDirectory;
 }

packages/flutter_tools/test/general.shard/base/file_system_test.dart

@@ -7,6 +7,7 @@ import 'dart:io' as io;
 
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
+import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
 import 'package:flutter_tools/src/base/platform.dart';
@@ -15,6 +16,13 @@ import 'package:test/fake.dart';
 
 import '../../src/common.dart';
 
+class LocalFileSystemFake extends LocalFileSystem {
+  LocalFileSystemFake.test({required super.signals}) : super.test();
+
+  @override
+  Directory get superSystemTempDirectory => directory('/does_not_exist');
+}
+
 void main() {
   group('fsUtils', () {
     late MemoryFileSystem fs;
@@ -174,6 +182,23 @@ void main() {
 
       expect(temp.existsSync(), isFalse);
     });
+
+    testWithoutContext('throwToolExit when temp not found', () async {
+      final Signals signals = Signals.test();
+      final LocalFileSystemFake localFileSystem = LocalFileSystemFake.test(
+        signals: signals,
+      );
+
+      try {
+        localFileSystem.systemTempDirectory;
+        fail('expected tool exit');
+      } on ToolExit catch(e) {
+        expect(e.message, 'Your system temp directory (/does_not_exist) does not exist. '
+            'Did you set an invalid override in your environment? '
+            'See issue https://github.com/flutter/flutter/issues/74042 for more context.'
+        );
+      }
+    });
   });
 }