C#: Fix FPs in RedundantToStringCall.ql#21726
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hvitved merged 4 commits intogithub:mainfrom Apr 17, 2026
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Pull request overview
This PR updates the C# RedundantToStringCall query and its tests to avoid false positives in cases where an explicit ToString() call is not actually redundant (notably base.ToString() and StringBuilder.AppendLine(...)).
Changes:
- Extend the query to exclude
base.ToString()from being reported as redundant. - Refine the
ImplicitToStringExprmodeling forStringBuilderto coverAppend(...)but notAppendLine(...). - Migrate/expand the query test to inline expectations (
// $ Alert) and update expected results accordingly.
Show a summary per file
| File | Description |
|---|---|
| csharp/ql/test/query-tests/Useless Code/RedundantToStringCall/RedundantToStringCallBad.cs | Adds inline expectation marker for the “bad” string.Format(... o.ToString()) case. |
| csharp/ql/test/query-tests/Useless Code/RedundantToStringCall/RedundantToStringCall.qlref | Switches to structured qlref with postprocessing via InlineExpectationsTestQuery.ql. |
| csharp/ql/test/query-tests/Useless Code/RedundantToStringCall/RedundantToStringCall.expected | Updates expected locations and adds the new StringBuilder.Append(o.ToString()) alert. |
| csharp/ql/test/query-tests/Useless Code/RedundantToStringCall/RedundantToStringCall.cs | Adds StringBuilder scenarios and inline expectations; includes a base.ToString() “GOOD” regression case. |
| csharp/ql/src/Useless code/RedundantToStringCall.ql | Excludes base.ToString() from results to prevent false positives. |
| csharp/ql/lib/semmle/code/csharp/commons/Strings.qll | Restricts StringBuilder implicit-ToString context to Append (not AppendLine). |
Copilot's findings
- Files reviewed: 6/6 changed files
- Comments generated: 0
geoffw0
previously approved these changes
Apr 17, 2026
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geoffw0
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geoffw0
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LGTM, couple of questions because my C# knowledge is limited.
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|
Changes look good, but perhaps make a change note (false positive removal & query alert message changed); Test output needs to be updated. |
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