New .NET 7 Regex Source Generator: Syntax too obtrusive

[SetTrend]

The new feature is nice, but I believe it suffers from a very obtrusive syntax.

Couldn't you make an attribute or keyword alone (e.g. const) do the job at compile time to switch the Regular Expression to the new Regex Source Generator?

[huoyaoyuan]

The generator belongs to dotnet/runtime repo.
The syntax looks necessary to me.

Couldn't you make an attribute or keyword alone (e.g. const) do the job at compile time to switch the Regular Expression to the new Regex Source Generator?

It can hardly be "switching". The code structure of using source generator and using constructor are fundamentally different. A method (or partial property, if it exists) is necessary to wrap the details.

[HaloFour]

The compiler does trigger the source generator. Source generators can then generate additional C# source which is added to the compilation, but they cannot modify any existing source. This generator keys off of an existing partial method that has the RegexGenerator attribute and uses that to emit an implementation to the partial method, which the compiler then combines into a single actual method.

[jnm2]

You can also view the generated partial class that adds the functionality within the Analyzers node of the project in Solution Explorer, to see what is necessary to generate to get this functionality to work.

[333fred]

@SetTrend to be more explicit, source generators are user authored code. The user in this case happens to be the standard library, but you could write your own generator using the same system and the compiler would know as much about it as it knows about the regex generator.

[SetTrend]

Thanks to all of you for clarifying this. I just read through the Roslyn Source Generators documentation. I now see it's a more general approach, and compiled Regular Expressions is rather one implementation of such Source Generator.

[jnm2]

Though, one could imagine inventing a syntax compilers could generally use to do this sort of thing inline without requiring a partial method declaration, with full generality and applications outside regex. It sounds like a hard sell.

[RenderMichael]

I think it could be improved with the introduction of partial properties. since the method call might give the impression that there's computation going on.