Resolve interceptor location using identifier name (#50245)

* Resolve interceptor location using identifier name

* Address feedback

Author: captainsafia

src/Http/Http.Extensions/gen/StaticRouteHandlerModel/Endpoint.cs

@@ -142,14 +142,23 @@ public static int GetSignatureHashCode(Endpoint endpoint)
 
     private static (string, int, int) GetLocation(IInvocationOperation operation)
     {
-        var operationSpan = operation.Syntax.Span;
+        // The invocation expression consists of two properties:
+        // - Expression: which is a `MemberAccessExpressionSyntax` that represents the method being invoked.
+        // - ArgumentList: the list of arguments being invoked.
+        // Here, we resolve the `MemberAccessExpressionSyntax` to get the location of the method being invoked.
+        var memberAccessorExpression = ((MemberAccessExpressionSyntax)((InvocationExpressionSyntax)operation.Syntax).Expression);
+        // The `MemberAccessExpressionSyntax` in turn includes three properties:
+        // - Expression: the expression that is being accessed.
+        // - OperatorToken: the operator token, typically the dot separate.
+        // - Name: the name of the member being accessed, typically `MapGet` or `MapPost`, etc.
+        // Here, we resolve the `Name` to extract the location of the method being invoked.
+        var invocationNameSpan = memberAccessorExpression.Name.Span;
+        // Resolve LineSpan associated with the name span so we can resolve the line and character number.
+        var lineSpan = operation.Syntax.SyntaxTree.GetLineSpan(invocationNameSpan);
+        // Resolve the filepath of the invocation while accounting for source mapped paths.
         var filePath = operation.Syntax.SyntaxTree.GetInterceptorFilePath(operation.SemanticModel?.Compilation.Options.SourceReferenceResolver);
-        var span = operation.Syntax.SyntaxTree.GetLineSpan(operationSpan);
-        var lineNumber = span.StartLinePosition.Line + 1;
-        // Calculate the character offset to the end of the Map invocation detected
-        var invocationLength = ((MemberAccessExpressionSyntax)((InvocationExpressionSyntax)operation.Syntax).Expression).Expression.Span.Length;
-        var characterNumber = span.StartLinePosition.Character + invocationLength + 2;
-        return (filePath, lineNumber, characterNumber);
+        // LineSpan.LinePosition is 0-indexed, but we want to display 1-indexed line and character numbers in the interceptor attribute.
+        return (filePath, lineSpan.StartLinePosition.Line + 1, lineSpan.StartLinePosition.Character + 1);
     }
 
     private static string GetHttpMethod(IInvocationOperation operation)

src/Http/Http.Extensions/test/RequestDelegateGenerator/CompileTimeCreationTests.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 using System.Collections.Immutable;
+using System.Globalization;
 using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.AspNetCore.Http.RequestDelegateGenerator;
@@ -96,6 +97,57 @@ public async Task SupportsDifferentInterceptorsFromSameLocation()
         await VerifyAgainstBaselineUsingFile(updatedCompilation);
     }
 
+    [Fact]
+    public async Task SupportsMapCallOnNewLine()
+    {
+        var source = """
+app
+     .MapGet("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions
+    .MapGet(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+app.
+    MapGet("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions.
+   MapGet(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+app.
+MapGet("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions.
+MapGet(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+app.
+
+
+MapGet("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions.
+
+
+MapGet(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+app.
+MapGet
+("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions.
+   MapGet
+(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+app
+.
+MapGet
+("/hello1/{id}", (int id) => $"Hello {id}!");
+EndpointRouteBuilderExtensions
+.
+   MapGet
+(app, "/hello2/{id}", (int id) => $"Hello {id}!");
+""";
+        var (_, compilation) = await RunGeneratorAsync(source);
+        var endpoints = GetEndpointsFromCompilation(compilation);
+
+        for (int i = 0; i < endpoints.Length; i++)
+        {
+            var httpContext = CreateHttpContext();
+            httpContext.Request.RouteValues["id"] = i.ToString(CultureInfo.InvariantCulture);
+            await endpoints[i].RequestDelegate(httpContext);
+            await VerifyResponseBodyAsync(httpContext, $"Hello {i}!");
+        }
+    }
+
     [Fact]
     public async Task SourceMapsAllPathsInAttribute()
     {