System.Text.RegularExpressions.Tests.RegexMatchTests.CharClassSubtraction_DeepNesting_DoesNotStackOverflow(engine: NonBacktracking) [FAIL]
System.PlatformNotSupportedException
Stack Trace:
at System.Text.RegularExpressions.Symbolic.SymbolicRegexRunnerFactory..ctor(RegexTree regexTree, RegexOptions options, TimeSpan matchTimeout)
On browser-wasm (single-threaded), the deep nesting with the NonBacktracking engine triggers internal threading APIs (Task.InternalWaitCore → ThrowIfMultithreadingIsNotSupported) that are not supported. The NonBacktracking engine works fine on browser-wasm for normal patterns — only this extreme nesting depth triggers the threading code path. The fix is an in-test guard that skips only NonBacktracking on Browser, keeping Interpreter and Compiled coverage.
Not related to any PR changes ΓÇö this is a main-branch regression in test coverage.
{
"ErrorPattern": "[FAIL].*_DeepNesting_DoesNotStackOverflow",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1314573
Build error leg or test failing:
CharClassSubtraction_DeepNesting_DoesNotStackOverflowwithNonBacktrackingengine on browser-wasmPull request: #124125
Details
The test
CharClassSubtraction_DeepNesting_DoesNotStackOverflowwas added in #124995 (commit 50f4fec, merged Feb 27). It runs across allRegexEnginevalues viaAvailableEngines_MemberData, includingNonBacktracking.On browser-wasm (single-threaded), the deep nesting with the NonBacktracking engine triggers internal threading APIs (
Task.InternalWaitCore→ThrowIfMultithreadingIsNotSupported) that are not supported. The NonBacktracking engine works fine on browser-wasm for normal patterns — only this extreme nesting depth triggers the threading code path. The fix is an in-test guard that skips only NonBacktracking on Browser, keeping Interpreter and Compiled coverage.Affects 3 browser-wasm LibraryTests jobs:
LibraryTests browser-wasm linux ReleaseLibraryTests_EAT browser-wasm linux ReleaseLibraryTests browser-wasm windows ReleaseNot related to any PR changes ΓÇö this is a main-branch regression in test coverage.
Error Message
{ "ErrorPattern": "[FAIL].*_DeepNesting_DoesNotStackOverflow", "BuildRetry": false, "ExcludeConsoleLog": false }Known issue validation
Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1314573
Error message validated:
[[FAIL].*_DeepNesting_DoesNotStackOverflow]Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/1/2026 3:37:52 AM UTC
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