Aspnetcore.docs: Undocumented breaking change in IApplicationBuilder.UseExceptionHandler()

[evil-shrike]

The migration guide doesn't notice anything about UseExceptionHandler. Usage of a simple call app.UseExceptionHandler() in one's Startup.Configure will fail at runtime with the exception:
System.InvalidOperationException: 'An error occurred when configuring the exception handler middleware. Either the 'ExceptionHandlingPath' or the 'ExceptionHandler' option must be set in 'UseExceptionHandler()'.'

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Document Details

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• ID: 4fa0f562-bdf0-eeea-f076-0c3e05222f75
• Version Independent ID: 8269d917-3b32-1607-71da-c756d4d7ad32
• Content: Migrate from ASP.NET Core 2.0 to 2.1
• Content Source: aspnetcore/migration/20_21.md
• Product: asp.net-core
• GitHub Login: @Rick-Anderson
• Microsoft Alias: riande

[Rick-Anderson]

The templates use the overload of UseExceptionHandler that takes an errorHandlingPath parm
app.UseExceptionHandler("/Error");

@Tratcher this seems like an edge case with great error message. Should this be added to doc?

[Tratcher]

See https://github.com/aspnet/Diagnostics/issues/400. This wasn't a breaking change per-se, it didn't work before either. 2.1 added an exception to explain why it is mis-configured.