microsoft / microsoft/vs-threading
Analyzer should produce error when awaiting an expression including a null-conditional operator
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- C#
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Description
Is your feature request related to a problem? Please describe.
I occasionally see code such as this:
await foo?.BarAsync();
This will throw NullReferenceException if foo is null.
Describe the solution you'd like
An analyzer should produce an error when code like the above is encountered.
Note that this syntax however would be OK:
await foo?.BarAsync() ?? Task.CompletedTask;
We should also make sure the code fix for VSTHRD002, VSTHRD103 (and perhaps others?) that doesn't turn foo?.Bar() to await foo?.Bar() as that would introduce this problem. It should instead use await foo?.Bar() ?? TplExtensions.CompletedTask.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the analyzers and code fixes for VSTHRD002 and VSTHRD103, then trace how they handle null-conditional expressions. The work is done when awaiting a possibly null task is diagnosed, the null-coalescing form is accepted, and relevant code fixes do not introduce the unsafe pattern.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- csharp
- Domain
- devtools
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100