Return nil on applying() failure instead of crashing #26575
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@swift-ci Please test |
numist
commented
Aug 8, 2019
| target.append(contentsOf: source[start..<index]) | ||
| } | ||
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| difference._fastEnumeratedApply { change in |
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This hunk is all whitespace changes with the exception of the addition of a do { … } catch { … } block and associated sprinklings of try.
lorentey
approved these changes
Aug 9, 2019
lorentey
reviewed
Aug 9, 2019
| let start = index | ||
| source.formIndex(&index, offsetBy: count) | ||
| if !source.formIndex(&index, offsetBy: count, limitedBy: source.endIndex) { | ||
| throw _ApplicationError.failed |
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These throws may throw off people who break on all throws. We can fix this later if it proves annoying.
xwu
reviewed
Aug 9, 2019
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The application of a diff onto an invalid base state is supposed to cause
nilto be returned fromapplying(), but instead it just crashes with an index out of bounds error.Oops.
Generally speaking maintaining consistent diff and base states is the programmer's responsibility, but not crashing on invalid application is necessary for diffs to be useful as a boundary type for passing between modules so someone else's bug doesn't turn into anyone else's crash.
This PR includes exhaustive coverage of the boundary between application success and failure as well as fixes for the failing tests, including the test from the original report.
Resolves <rdar://problem/53663769>