Setting the file. One moment.
Subchapter 2.1
references/aot_sdk_discovery.mdMarkdown4 KBView on GitHub
Guidance on locating the Dart SDK and spawning Dart child processes across JIT (dart run, pub global activate) and standalone AOT (dart compile exe, dart install) execution modes.
When writing CLI developer tools that spawn dart child processes (e.g. running build_runner, dart format, dart test, or code analyzers), developers frequently write:
// ❌ WRONG: Breaks when compiled to AOT
final dart = Platform.resolvedExecutable;
final sdkDir = path.dirname(path.dirname(dart));dart run, pub global activate): Platform.resolvedExecutable points directly to <dart-sdk>/bin/dart. Calling dirname(dirname(...)) resolves to the valid SDK root directory.dart compile exe, dart install): Platform.resolvedExecutable points to the compiled application binary (e.g. ~/.dart/install/app-bundles/my_cli/.../bin/my_cli).Platform.resolvedExecutable expecting the dart VM, it spawns itself recursively.--observe, --enable-vm-service) or tool subcommands (like run, format, or test), the compiled binary fails immediately with unknown option errors.Platform.resolvedExecutable to locate SDK resources (such as libraries.json) fails because the binary resides in an application bundle directory rather than a Dart SDK installation.Do not write bespoke SDK discovery probes. Depend on package:cli_util (version 0.6.0 or higher), which provides memoized, nullable getters (dartExecutable and sdkPath) that locate the Dart SDK across both JIT and AOT environments:
import 'dart:io' as io;
import 'package:cli_util/cli_util.dart' as cli_util;
Future<void> runSubprocess() async {
// Resolves the dart executable across both JIT and AOT environments
final dartExe = cli_util.dartExecutable;
if (dartExe == null) {
io.stderr.writeln('Error: Could not locate the Dart SDK on PATH.');
io.exitCode = 1;
return;
}
final result = await io.Process.run(dartExe, ['format', '.']);
io.stdout.write(result.stdout);
io.stderr.write(result.stderr);
}A valid Dart SDK and dart executable may reside in several environmental locations across different developer setups:
Platform.resolvedExecutable): When running on the JIT VM (dart run), resolvedExecutable points directly to <dart-sdk>/bin/dart.DART_SDK): Defined when a developer explicitly points DART_SDK to an SDK installation directory.PATH: Resolved via system PATH entries (dart, dart.exe, or dart.bat), including dereferencing symlinks and checking bin/cache/dart-sdk for Flutter installations.FLUTTER_ROOT): Bundled under FLUTTER_ROOT/bin/cache/dart-sdk.The exact search order and SDK directory validation logic should be delegated to package:cli_util rather than re-implemented in application code.
When executing child subprocesses from a Dart CLI:
cli_util.dartExecutable: Never pass Platform.executable or Platform.resolvedExecutable.'dart' on PATH: If package:cli_util is not an option, execute the literal string 'dart' directly via Process.start('dart', [...], runInShell: Platform.isWindows).dart.bat in flutter/bin. Invoking batch files directly via Process.start requires runInShell: true unless pointing to the resolved binary dart.exe.