Routing with common prefix

[MichalSznajder]

Assume app with following routes:

app.MapGet("/first", () => "First");
app.MapGet("/{param}/second", () => "Second");

In this scenario accessing /first/second will result in response Second.

After some debugging I found following code in DfaMarcher

aspnetcore/src/Http/Routing/src/Matching/DfaMatcherBuilder.cs

Lines 330 to 336 in 97c6f0d

	}
	else
	{
	// This means the current parameter we are evaluating doesn't contain any constraint, so we need to
	// traverse all literal nodes as well as the parameter node.
	nextParents.AddRange(parent.Literals.Values);
	}

This results with DfaMatcher table looking like this:

/first/ HTTP: GET -> 'HTTP: GET /first' 
/first/ HTTP: * -> '405 HTTP Method Not Supported' 
/first/second/ HTTP: GET -> 'HTTP: GET /{param}/second' 
/first/second/ HTTP: * -> '405 HTTP Method Not Supported' 
/{...}/second/ HTTP: GET -> 'HTTP: GET /{param}/second' 
/{...}/second/ HTTP: * -> '405 HTTP Method Not Supported' 

#38117 mentions

We've seen some issues with large DFAs as a result of some patterns that involve a large amount of variable prefixes. We've done work in 6.0 to address this via automatically trimming the DFA we generate by leveraging existing route constraints as well as the existing structure in complex segments.

so I tried

app.MapGet("/first", () => "First");
app.MapGet("/{param:int}/second", () => "Second");

that results in DfaTable of:

/first/ HTTP: GET -> 'HTTP: GET /first' 
/first/ HTTP: * -> '405 HTTP Method Not Supported' 
/{...}/second/ HTTP: GET -> 'HTTP: GET /{param}/second' 
/{...}/second/ HTTP: * -> '405 HTTP Method Not Supported' 

However I would like param to be anything and /first/second return "First".

Is there a way to change it in automatic way?

[gfoidl]

@MichalSznajder I created an issue #58838 for this. Let's continue over there.

Thanks for raising that concern anyway!