New route analysers don't appear to support regex

[mcm-ham]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

After upgrading to .NET 8 this line:

[HttpGet(@"{platform:alpha}/{locale:regex([[a-z]]+(-[[a-z]]+)?)}")]

Now generates these errors

I18nController.cs(26,66): error ASP0017: Route issue: There is an incomplete parameter in the route template. Check that each '{' character has a matching '}' character. (https://aka.ms/aspnet/analyzers)
I18nController.cs(26,66): error ASP0017: Route issue: There is an incomplete parameter in the route template. Check that each '{' character has a matching '}' character. (https://aka.ms/aspnet/analyzers)
I18nController.cs(26,32): error ASP0017: Route issue: An optional parameter must be at the end of the segment. In the segment '{locale:regex([[a-z]]+(-[[a-z]]+)?)}', optional parameter 'locale' is followed by ')}'. (https://aka.ms/aspnet/analyzers)

Do these new analysers support regex constraint?

Expected Behavior

The new analysers to support regex constraint.

Steps To Reproduce

https://github.com/mcm-ham/bugrepro-routeissue

Exceptions (if any)

No response

.NET Version

8.0.100

Anything else?

dotnet info
.NET SDK:
Version: 8.0.100
Commit: 57efcf1350
Workload version: 8.0.100-manifests.6c33ef20

Runtime Environment:
OS Name: Mac OS X
OS Version: 14.1
OS Platform: Darwin
RID: osx-arm64
Base Path: /usr/local/share/dotnet/sdk/8.0.100/

.NET workloads installed:
Workload version: 8.0.100-manifests.6c33ef20
There are no installed workloads to display.

Host:
Version: 8.0.0
Architecture: arm64
Commit: 5535e31a71

.NET SDKs installed:
6.0.414 [/usr/local/share/dotnet/sdk]
7.0.401 [/usr/local/share/dotnet/sdk]
8.0.100 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.22 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.11 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.22 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.11 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
None

Environment variables:
Not set

vscode about
Version: 1.84.2
Commit: 1a5daa3a0231a0fbba4f14db7ec463cf99d7768e
Date: 2023-11-09T10:52:57.054Z
Electron: 25.9.2
ElectronBuildId: 24603566
Chromium: 114.0.5735.289
Node.js: 18.15.0
V8: 11.4.183.29-electron.0
OS: Darwin arm64 23.1.0

[david-acker]

The issue appears to be caused by the optional group in the locale, since [[a-z]]+(-[[a-z]]+) works as expected. It also looks like this is an issue with the route constraints themselves, not just the analyzer.

I haven't been able to find any examples of regex constraints with an optional group in the docs, but I also haven't found any mention of why this isn't or wouldn't be supported, so this seems like a bug to me.

[codetuner]

I have the same issue here with a regex to match cultures ("xx" or "xx-YY" formats with a default to "en"):

app.MapControllerRoute(
    name: "default",
    pattern: "{culture:regex(^[a-z][a-z](\\-[A-Z][A-Z])?$)=en}/{controller=Home}/{action=Index}/{id?}");

It seems the question mark in the route constraint expression makes the code analysis parser think the constraint ends here and the route element is optional. Which is incorrect.

By way of workaround, replacing the "?" quantifier by the "{0,1}" quantifier makes code analysis not complain anymore:

app.MapControllerRoute(
    name: "default",
    pattern: "{culture:regex(^[a-z][a-z](\\-[A-Z][A-Z]){{0,1}}$)=en}/{controller=Home}/{action=Index}/{id?}");

In both versions, the route constraint seems to work fine. The only issue is the code analysis complaining about the first version.