feat: add for support AOT request routing

[TimothyMakkison]

Adds AOT support for request routing

• Supports standard parameter routing
• Supports object property routing
• Emits an exception if round trip parameter is used with the wrong type
• Emits a guard check if an unmatched route parameter is found
• Supports ICustomAttributeProvider by caching ParameterInfo and PropertyInfo lookups in a ConcurrentDictionary
  • Note that it would be possible to calculate these values once when a class is first constructed and store them as static fields in the generated class, I chose this solution as it is easier from a code gen perspective. Note that fields may be faster than a ConcurrentDictionary
• Parsing logic is based upon RestMethodInfoInternal and emitting logic is based upon RequestBuilderImplementation.RequestBuilding
• Generated code either uses current solution or uses a series of ValueStringBuilder calls
• Should be fairly easy to add query support after

Haven't added tests or cleaned up yet, would like to hear feed back before doing anything more.

• ValueStringbuilder is currently public, I suspect it could be emitted once within internal partial class Generated

[Get("/{unmatched}/{id}/hello/{val.Value}/{**round}")]
public Task<ApiResponse<List<User>>> GetUsers(MyData val, int id, string round);

var refitSettings = _settings;
var valueStringBuilder = new global::Refit.ValueStringBuilder(stackalloc char[256]);
valueStringBuilder.Append("/");
global::Refit.GeneratedRequestRunner.UnmatchedRouteParameterGuard(refitSettings, "URL /{unmatched}/{id}/hello/{val.Value} has parameter unmatched, but no method parameter matches");
valueStringBuilder.Append("{unmatched}");
valueStringBuilder.Append("/");
global::Refit.GeneratedRequestRunner.AddStandardParameter(ref valueStringBuilder, id, false, refitSettings, typeof(global::Refit.Benchmarks.ITest), "GetUsers", "id");
valueStringBuilder.Append("/hello/");
global::Refit.GeneratedRequestRunner.AppendObjectPropertyFragment(ref valueStringBuilder, val.Value, refitSettings, typeof(global::Refit.Benchmarks.ITest.MyData), "Value");
valueStringBuilder.Append("/");
global::Refit.GeneratedRequestRunner.AddStandardParameter(ref valueStringBuilder, round, true, refitSettings, typeof(global::Refit.Benchmarks.ITest), "GetUsers", "round");


var refitRequest = new global::System.Net.Http.HttpRequestMessage(global::System.Net.Http.HttpMethod.Get, global::Refit.GeneratedRequestRunner.BuildRelativeUri(this.Client, valueStringBuilder.ToString(), refitSettings.UrlResolution));
               

Note that the above code could probably be simplified with CalledMemberName and nameof

[TimothyMakkison]

Tests

Need to look into writing more tests, especially generated tests to ensure that exception generation and the unmatched route are emitted.

Failing tests

• Looking at the failing tests most of them are from [Bug]: derived types erroneously add additional query parameters. #1882, which were tests meant to verify that the "broken" behaviour is till present.
• GeneratedSourcesCompileWithCSharp73Baseline fails as stackalloc expressions aren't supported in that version of C#, TBH if this is an issue I can have the emitter check the language version and either emit new or stackalloc and get identical results.
• Tests are failing due reflection ambiguity when a method has multiple overloads, looking at my notes from Aot gen #1965 it's kind of tricky to do this in a performant way without adding a bunch of complexity or doing a lot of work when the generated class is first cctor'd

Tempted to try and add Query support in the same PR, happy to make a follow up Pr otherwise.

[glennawatson]

Hows this related to the work in #2174

[ChrisPulman]

@TimothyMakkison check the Slack messages :)