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gonenggoneng
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Guard against stale PBGitRevList parses overlapping (#563)
A burst of git-directory FSEvents (e.g. from `git switch -c <branch>` touching both a ref file and HEAD) can trigger overlapping loadRevisionsWithCompletionBlock: calls on the same PBGitRevList instance. The previous parse operation's trailing commit-batch flush is fire-and-forget and can still land after a newer parse has already reset/appended its own commits, since NSOperation.isCancelled is only checked cooperatively and can lose that race. The result is duplicate commits appended into the history list. Track a per-instance load generation and reject any updateCommits: flush whose generation no longer matches the current one, closing the race regardless of operation-queue/FSEvents timing.
1 parent 8951252 commit d9df533

1 file changed

Lines changed: 10 additions & 6 deletions

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‎Classes/git/PBGitRevList.m‎

Lines changed: 10 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,8 @@ @interface PBGitRevList ()
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@property (nonatomic, strong) NSOperationQueue *operationQueue;
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@property (nonatomic, assign) NSUInteger loadGeneration;
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@end
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@@ -62,6 +64,8 @@ - (void)loadRevisionsWithCompletionBlock:(void (^)(void))completionBlock
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self.resetCommits = YES;
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NSUInteger generation = ++self.loadGeneration;
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NSBlockOperation *parseOperation = [[NSBlockOperation alloc] init];
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__weak typeof(self) weakSelf = self;
@@ -75,7 +79,7 @@ - (void)loadRevisionsWithCompletionBlock:(void (^)(void))completionBlock
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GTEnumerator *enu = [[GTEnumerator alloc] initWithRepository:repo error:&error];
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[weakSelf setupEnumerator:enu forRevspec:weakSelf.currentRev];
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[weakSelf addCommitsFromEnumerator:enu operation:weakParseOperation];
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[weakSelf addCommitsFromEnumerator:enu operation:weakParseOperation generation:generation];
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}];
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[parseOperation setCompletionBlock:completionBlock];
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@@ -94,9 +98,9 @@ - (BOOL)isParsing
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}
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- (void)updateCommits:(NSArray<PBGitCommit *> *)revisions operation:(NSOperation *)operation
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- (void)updateCommits:(NSArray<PBGitCommit *> *)revisions operation:(NSOperation *)operation generation:(NSUInteger)generation
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{
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if (!revisions || [revisions count] == 0 || operation.cancelled)
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if (!revisions || [revisions count] == 0 || operation.cancelled || generation != self.loadGeneration)
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return;
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if (self.resetCommits) {
@@ -193,7 +197,7 @@ - (void)setupEnumerator:(GTEnumerator *)enumerator
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}
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}
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- (void)addCommitsFromEnumerator:(GTEnumerator *)enumerator operation:(NSOperation *)operation
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- (void)addCommitsFromEnumerator:(GTEnumerator *)enumerator operation:(NSOperation *)operation generation:(NSUInteger)generation
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{
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PBGitGrapher *g = [[PBGitGrapher alloc] init];
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__block NSDate *lastUpdate = [NSDate date];
@@ -248,7 +252,7 @@ - (void)addCommitsFromEnumerator:(GTEnumerator *)enumerator operation:(NSOperati
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NSArray<PBGitCommit *> *updatedRevisions = [revisions copy];
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dispatch_async(dispatch_get_main_queue(), ^{
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[self updateCommits:updatedRevisions operation:operation];
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[self updateCommits:updatedRevisions operation:operation generation:generation];
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});
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[revisions removeAllObjects];
@@ -266,7 +270,7 @@ - (void)addCommitsFromEnumerator:(GTEnumerator *)enumerator operation:(NSOperati
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NSArray<PBGitCommit *> *updatedRevisions = [revisions copy];
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dispatch_async(dispatch_get_main_queue(), ^{
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[self updateCommits:updatedRevisions operation:operation];
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[self updateCommits:updatedRevisions operation:operation generation:generation];
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});
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}
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