Add side-effect free debugger display to ValueStringBuilder.
#122265
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Calling `ToString()` clears the builder, which can cause surprises when debugging.
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Pull request overview
This PR adds a side-effect free debugger display to both versions of ValueStringBuilder to address the problematic behavior where calling ToString() clears the builder, which causes unexpected issues during debugging.
Key changes:
- Added
[DebuggerDisplay]attribute to bothValueStringBuilderandValueStringBuilder<TChar>structs - Created side-effect free
DebuggerDisplayproperties that display the builder's content without clearing it - Refactored
ValueStringBuilder<TChar>.ToString()to extract string generation logic into a separateGetString()method
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/libraries/Common/src/System/Text/ValueStringBuilder.cs | Added [DebuggerDisplay] attribute and DebuggerDisplay property that uses AsSpan().ToString() for side-effect free debugging |
| src/libraries/Common/src/System/Text/ValueStringBuilder_1.cs | Added [DebuggerDisplay] attribute, extracted GetString() method for reuse, and added DebuggerDisplay property that calls GetString() for side-effect free debugging |
| } | ||
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| // ToString() clears the builder, so we need a side-effect free debugger display. | ||
| private string DebuggerDisplay => AsSpan().ToString(); |
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The DebuggerDisplay property should be marked as readonly for consistency with the generic version in ValueStringBuilder_1.cs and to clearly indicate it doesn't mutate state. The property only reads from the builder without modifying it.
private readonly string DebuggerDisplay => AsSpan().ToString();
Suggested change
| private string DebuggerDisplay => AsSpan().ToString(); | |
| private readonly string DebuggerDisplay => AsSpan().ToString(); |
stephentoub
reviewed
Dec 7, 2025
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Calling
ToString()clears the builder, which can cause surprises when debugging.