Fix chart showing No Data on rapid period switching#1816
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Ignore cancelled task errors instead of setting error state
Summary of ChangesHello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request enhances the robustness of chart and portfolio data loading by implementing cooperative task cancellation. The changes ensure that when a user rapidly changes the selected period, previous, now-irrelevant data fetching tasks are properly cancelled and their potential errors are ignored, preventing the UI from showing incorrect 'No Data' or error messages and providing a smoother user experience. Highlights
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Code Review
This pull request addresses an issue where charts show 'No Data' during rapid period switching by ignoring errors from cancelled tasks. The approach of adding cancellation points with Task.checkCancellation() and handling cancellation in catch blocks is correct. However, the implementation can be made more robust. Instead of checking Task.isCancelled, it's safer to specifically check if the caught error is a CancellationError. This prevents accidentally swallowing other legitimate errors that might occur while the task is in a cancelled state. I've added suggestions to make this change in all affected files.
| ) | ||
| chartState = .data(model) | ||
| } catch { | ||
| guard !Task.isCancelled else { return } |
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While checking Task.isCancelled works for the intended purpose of ignoring cancellation errors, it can lead to swallowing non-cancellation errors if the task happens to be cancelled when another error is thrown. A more robust approach is to check if the caught error is specifically a CancellationError.
| guard !Task.isCancelled else { return } | |
| guard !(error is CancellationError) else { return } |
| } | ||
| state = .data(data) | ||
| } catch { | ||
| guard !Task.isCancelled else { return } |
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While checking Task.isCancelled works for the intended purpose of ignoring cancellation errors, it can lead to swallowing non-cancellation errors if the task happens to be cancelled when another error is thrown. A more robust approach is to check if the caught error is specifically a CancellationError.
| guard !Task.isCancelled else { return } | |
| guard !(error is CancellationError) else { return } |
| let chart = ChartValuesViewModel.priceChange(charts: charts, period: selectedPeriod, formatter: currencyFormatter, showHeaderValue: true) | ||
| state = chart.map { .data(WalletPortfolioData(chart: $0, portfolio: portfolio)) } ?? .noData | ||
| } catch { | ||
| guard !Task.isCancelled else { return } |
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While checking Task.isCancelled works for the intended purpose of ignoring cancellation errors, it can lead to swallowing non-cancellation errors if the task happens to be cancelled when another error is thrown. A more robust approach is to check if the caught error is specifically a CancellationError.
| guard !Task.isCancelled else { return } | |
| guard !(error is CancellationError) else { return } |
| assetId: assetModel.asset.id, | ||
| period: selectedPeriod | ||
| ) | ||
| try Task.checkCancellation() |
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try Task.checkCancellation() is unnecessary in here - task(id:) already propagates cancellation through try await
| state = .loading | ||
| do { | ||
| let data = try await perpetualService.portfolio(address: address) | ||
| try Task.checkCancellation() |
| do { | ||
| let rate = try priceService.getRate(currency: currencyCode) | ||
| let portfolio = try await service.getPortfolioAssets(assets: assets, period: selectedPeriod) | ||
| try Task.checkCancellation() |
| ) | ||
| chartState = .data(model) | ||
| } catch { | ||
| guard !Task.isCancelled else { return } |
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lets use for consistency?
if !error.isCancelled {
chartState = .error(error)
}
Extract cancellation-aware error handling into a reusable setError method on StateViewType, replacing manual `if !error.isCancelled` checks across 10 call sites.
2 participants
Ignore cancelled task errors instead of setting error state