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Add orElse callbacks and RetryExhaustedException when retries is exhausted. #184

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Add orElse callbacks and RetryExhaustedException when retries is exhausted. #184

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40 changes: 37 additions & 3 deletions retry/lib/retry.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -118,10 +118,16 @@ class RetryOptions {
/// If no [retryIf] function is given this will retry any for any [Exception]
/// thrown. To retry on an [Error], the error must be caught and _rethrown_
/// as an [Exception].
///
/// if retries is exhausted, the result of invoking the [orElse] function is returned.
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@jonasfj jonasfj Sep 12, 2022

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Capitalize

///
/// If [orElse] is omitted, it defaults to throwing a [RetryExhaustedException]
/// when retries is exhausted.
Future<T> retry<T>(
FutureOr<T> Function() fn, {
FutureOr<bool> Function(Exception)? retryIf,
FutureOr<void> Function(Exception)? onRetry,
FutureOr<T> Function(Exception)? orElse,
}) async {
var attempt = 0;
// ignore: literal_only_boolean_expressions
Expand All @@ -130,8 +136,14 @@ class RetryOptions {
try {
return await fn();
} on Exception catch (e) {
if (attempt >= maxAttempts ||
(retryIf != null && !(await retryIf(e)))) {
if (attempt >= maxAttempts) {
if (orElse != null) {
return await orElse(e);
} else {
throw RetryExhaustedException(attempt, e);
}
}
if (retryIf != null && !(await retryIf(e))) {
rethrow;
}
if (onRetry != null) {
Expand Down Expand Up @@ -171,6 +183,11 @@ class RetryOptions {
/// If no [retryIf] function is given this will retry any for any [Exception]
/// thrown. To retry on an [Error], the error must be caught and _rethrown_
/// as an [Exception].
///
/// if retries is exhausted, the result of invoking the [orElse] function is returned.
///
/// If [orElse] is omitted, it defaults to throwing a [RetryExhaustedException]
/// when retries is exhausted.
Future<T> retry<T>(
FutureOr<T> Function() fn, {
Duration delayFactor = const Duration(milliseconds: 200),
Expand All @@ -179,10 +196,27 @@ Future<T> retry<T>(
int maxAttempts = 8,
FutureOr<bool> Function(Exception)? retryIf,
FutureOr<void> Function(Exception)? onRetry,
FutureOr<T> Function(Exception)? orElse,
}) =>
RetryOptions(
delayFactor: delayFactor,
randomizationFactor: randomizationFactor,
maxDelay: maxDelay,
maxAttempts: maxAttempts,
).retry(fn, retryIf: retryIf, onRetry: onRetry);
).retry(fn, retryIf: retryIf, onRetry: onRetry, orElse: orElse);

/// throw [RetryExhaustedException] when retries is exhausted.
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@jonasfj jonasfj Sep 12, 2022

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Capitalize

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@drown0315 drown0315 Sep 18, 2022

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This is a breaking change, even if orElse is omitted.

Is it really better to get a retries exhausted exception, rather than throwing the last exception that was caught?

We'd need to investigate of breaking this package would affect many users.

I think the reason you need RetryExhaustException is that when you need to do subsequent processing for a retry failure, you need to repeatedly use the logic in retryIf to determine if the exception is a failed retry.

Maybe not needing RetryExhaustException, orElse to handle only the retryIf exceptions is a better way?

But here the RetryExhaustException throwing should rely on retryIf, a little embarrassing😅.

class RetryExhaustedException implements Exception {
final int attempt;
final dynamic exception;

RetryExhaustedException(
this.attempt,
this.exception,
);

@override
String toString() {
return 'RetryExhaustedException{attempt: $attempt, exception: $exception}';
}
}
110 changes: 65 additions & 45 deletions retry/test/retry_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -77,59 +77,79 @@ void main() {
count++;
throw FormatException('Retry will fail');
}, retryIf: (e) => e is FormatException);
await expectLater(f, throwsA(isFormatException));
await expectLater(
f,
throwsA(predicate((e) =>
e is RetryExhaustedException &&
e.attempt == 5 &&
e.exception is FormatException)));
expect(count, equals(5));
});

test('retry (success after 2)', () async {
test('retry (orElse, exhaust retries)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
final v = await retry(
() async {
count++;
throw Exception();
},
retryIf: (e) => true,
orElse: (_) => 1,
maxAttempts: 3,
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
return true;
}, retryIf: (e) => e is FormatException);
await expectLater(f, completion(isTrue));
expect(count, equals(2));
expect(count, 3);
expect(v, 1);
});
});

test('retry (no retryIf)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
return true;
});
await expectLater(f, completion(isTrue));
expect(count, equals(2));
});
test('retry (success after 2)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
return true;
}, retryIf: (e) => e is FormatException);
await expectLater(f, completion(isTrue));
expect(count, equals(2));
});

test('retry (unhandled on 2nd try)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
throw Exception('unhandled thing');
}, retryIf: (e) => e is FormatException);
await expectLater(f, throwsA(isException));
expect(count, equals(2));
test('retry (no retryIf)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
return true;
});
await expectLater(f, completion(isTrue));
expect(count, equals(2));
});

test('retry (unhandled on 2nd try)', () async {
var count = 0;
final r = RetryOptions(
maxAttempts: 5,
maxDelay: Duration(),
);
final f = r.retry(() {
count++;
if (count == 1) {
throw FormatException('Retry will be okay');
}
throw Exception('unhandled thing');
}, retryIf: (e) => e is FormatException);
await expectLater(f, throwsA(isException));
expect(count, equals(2));
});
}