Fix NullReferenceException when expanding property functions that return null #6414
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rainersigwald
approved these changes
May 5, 2021
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LGTM and I agree that we should take this in 16.10. @marcpopMSFT, any objection? The regression was reported by 1ES.
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| Expander<ProjectPropertyInstance, ProjectItemInstance> expander = new Expander<ProjectPropertyInstance, ProjectItemInstance>(pg, FileSystems.Default); | ||
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| string result = expander.ExpandIntoStringLeaveEscaped("$([System.Convert]::ChangeType(,$(SomeStuff.GetType())))", ExpanderOptions.ExpandProperties, MockElementLocation.Instance); |
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Was this just a fancy way to get null before, and you're using the easier approach now?
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It was not evaluating to null before so not hitting the intended code path. Presumably because the (, argument omission makes us pass an empty string.
Forgind
approved these changes
May 5, 2021
benvillalobos
approved these changes
May 5, 2021
| string result = expander.ExpandIntoStringLeaveEscaped("$([System.Convert]::ChangeType(,$(SomeStuff.GetType())))", ExpanderOptions.ExpandProperties, MockElementLocation.Instance); | ||
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| // The null-returning function is the only thing in the expression. | ||
| string result = expander.ExpandIntoStringLeaveEscaped("$([System.Environment]::GetEnvironmentVariable(`_NonExistentVar`))", ExpanderOptions.ExpandProperties, MockElementLocation.Instance); |
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I'm now reminded that if an environment var doesn't exist, GetEnvironmentVariable returns null.
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Fixes #6413
Context
This is a regression introduced in #6128. MSBuild crashes when evaluating a project where a property function returns null and its result is concatenated with another non-empty value.
Changes Made
Add a null check.
Testing
Fixed and extended the relevant test case.
Notes
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