[Backport] Request to backport PR #12063 (Remove regex from compiler) to .NET 8.0

[sam9191]

Summary

Requesting a backport of PR #12063 to the .NET 8.0 LTS branch. We are experiencing the exact RegexMatchTimeoutException in production that this PR fixes.

Related Issues/PRs

• Original issue: RegexMatchTimeoutException when rendering ViewComponent #12062
• Fix PR: Remove regex from the compiler #12063 (merged to main on July 30, 2025)

Environment

• .NET Version: 8.0 (LTS)
• Umbraco CMS: 13.7.2
• Hosting: Azure App Service (Linux)

Stack Trace from Production

System.Text.RegularExpressions.RegexMatchTimeoutException: The Regex engine has timed out while trying to match a pattern to an input string. This can occur for many reasons, including very large inputs or excessive backtracking caused by nested quantifiers, back-references and other factors.
at System.Text.RegularExpressions.RegexRunner.g__ThrowRegexTimeout|25_0()
at System.Text.RegularExpressions.RegexInterpreter.Scan(ReadOnlySpan`1 text)
at System.Text.RegularExpressions.Regex.RunAllMatchesWithCallbackTState
at System.Text.RegularExpressions.RegexReplacement.ReplaceNonSimpleText(...)
at System.Text.RegularExpressions.Regex.Replace(String input, String replacement)
at Microsoft.AspNetCore.Razor.Language.HtmlConventions.ToHtmlCase(String name)
at Microsoft.AspNetCore.Mvc.Razor.Extensions.ViewComponentTagHelperDescriptorFactory.CreateDescriptor(INamedTypeSymbol type)
at Microsoft.AspNetCore.Mvc.Razor.Extensions.ViewComponentTagHelperDescriptorProvider.Execute(TagHelperDescriptorProviderContext context)
at Microsoft.CodeAnalysis.Razor.CompilationTagHelperFeature.GetDescriptors()
at Microsoft.AspNetCore.Razor.Language.DefaultRazorTagHelperBinderPhase.ExecuteCore(RazorCodeDocument codeDocument)
...

Impact

• Frequency: Intermittent, affects production users
• User Impact: Complete page failure when rendering BlockGrid components

Justification for Backport

1. .NET 8.0 is an LTS release - Supported until November 2026, with many production workloads depending on it
2. Severity: This causes complete request failures in production
3. Low risk change - PR Remove regex from the compiler #12063 is a straightforward algorithm replacement (regex → loop) with comprehensive test coverage
4. Performance improvement - The fix also improves performance
5. No workaround - There is no configuration option to disable the regex or increase timeout in HtmlConventions.ToHtmlCase

Request

Please consider backporting PR #12063 to .NET 8 LTS so users can benefit from this critical fix.

Thank you for your consideration.

/cc @davidwengier

[davidwengier]

@dbreshears

[dbreshears]

@sam9191, is .NET 10 not available on the App Service Linux host or any reason you are not able install it and use it?

[sam9191]

We have many websites and just upgraded them to Umbraco 13 LTS, .NET 8 LTS.

We are planning to upgrade them all to the next LTS version by October this year, but until then hoping to get important fixes like this one as upgrading to .NET 10 would be a big task. Would you please consider backporting it to .NET 8.0?

[davidwengier]

Sorry, to be clear, you don't need to upgrade your projects to .NET 10, just installing the .NET 10 SDK (and if you have a global.json that pins you to 8, changing that to 10) should be enough to fix the issue for you. You can keep your projects all targeting .NET 8

[sam9191]

Thanks for the suggestion. While I understand using .NET 10 SDK is technically possible, for organizations with multiple projects, CI/CD pipelines, and SDK version policies, this represents significant coordination effort.

Given that .NET 8.0 is LTS (supported until Nov 2026), this is a production-breaking bug with no application-level workaround, and the fix is low-risk and already merged—would the team reconsider a backport? Other LTS users would benefit as well.

Thanks for all the work on this fix and for the quick response.