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make the log file test less flaky by retrying deletes and reads #180

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Merged
merged 1 commit into from
Jun 18, 2025
Merged

make the log file test less flaky by retrying deletes and reads #180

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42 changes: 35 additions & 7 deletions pkgs/dart_mcp_server/test/dart_tooling_mcp_server_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:async';
import 'dart:io';

import 'package:test/test.dart';
Expand All @@ -23,16 +24,43 @@ void main() {
});

test('logs traffic to a file', () async {
expect(
await File(logDescriptor.io.path).readAsLines(),
containsAll([
allOf(startsWith('<<<'), contains('"method":"initialize"')),
allOf(startsWith('>>>'), contains('"serverInfo"')),
allOf(startsWith('<<<'), contains('"notifications/initialized"')),
]),
// It may take a bit for all the lines to show up in the log.
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general question, are we writing to file with flush: true?

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We are calling flush on it after writing (we are opening the file and adding to the sink, then calling flush). In my experience on windows flush doesn't do anything though.

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Also the API says NOTE: This is not necessarily the same as the data being flushed by the operating system.

await doWithRetries(
() async => expect(
await File(logDescriptor.io.path).readAsLines(),
containsAll([
allOf(startsWith('<<<'), contains('"method":"initialize"')),
allOf(startsWith('>>>'), contains('"serverInfo"')),
allOf(startsWith('<<<'), contains('"notifications/initialized"')),
]),
),
);

// Ensure the file handle is released before the file is cleaned up.
await testHarness.serverConnectionPair.serverConnection.shutdown();

// Wait for the process to release the file.
await doWithRetries(() => File(logDescriptor.io.path).delete());
});
});
}

/// Performs [action] up to [maxRetries] times, backing off an extra 50ms
/// between each attempt.
FutureOr<T> doWithRetries<T>(
FutureOr<T> Function() action, {
int maxRetries = 5,
}) async {
var count = 0;
while (true) {
try {
return await action();
} catch (_) {
if (count == maxRetries) {
rethrow;
}
}
count++;
await Future<void>.delayed(Duration(milliseconds: 50 * count));
}
}
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