Removing from API Description parameters when inferred (FromPath) and not in the route

src/Mvc/Mvc.ApiExplorer/src/DefaultApiDescriptionProvider.cs

@@ -2,12 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Linq;
+using Microsoft.AspNetCore.Http.Metadata;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.ActionConstraints;
 using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.AspNetCore.Mvc.Infrastructure;
 using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Template;
 using Microsoft.Extensions.Options;
@@ -239,6 +241,7 @@ private void ProcessRouteParameters(ApiParameterContext context)
             routeParameters.Add(routeParameter.Name!, CreateRouteInfo(routeParameter));
         }
 
+        var inferredPathParametersToRemove = new List<ApiParameterDescription>();
         foreach (var parameter in context.Results)
         {
             if (parameter.Source == BindingSource.Path ||
@@ -258,9 +261,30 @@ private void ProcessRouteParameters(ApiParameterContext context)
                         parameter.Source = BindingSource.Path;
                     }
                 }
+                else
+                {
+                    if (parameter.Source == BindingSource.Path &&
+                        parameter.ModelMetadata is DefaultModelMetadata defaultModelMetadata &&
+                        !defaultModelMetadata.Attributes.Attributes.OfType<IFromRouteMetadata>().Any())
+                    {
+                        // If we didn't see the parameter in the route and no FromRoute metadata is set, it probably means
+                        // the parameter binding source was inferred (InferParameterBindingInfoConvention)  
+                        // probably because another route to this action contains it as route parameter.
+                        // let's add it to be removed from the API description
+                        inferredPathParametersToRemove.Add(parameter);
+                    }
+
+                }
             }
         }
 
+        // Remove all parameters detected as Inferred FromPath
+        // but that are not in the route
+        foreach (var inferredParameter in inferredPathParametersToRemove)
+        {
+            context.Results.Remove(inferredParameter);
+        }
+
         // Lastly, create a parameter representation for each route parameter that did not find
         // a partner.
         foreach (var routeParameter in routeParameters)

src/Mvc/Mvc.ApiExplorer/test/DefaultApiDescriptionProviderTest.cs

@@ -243,6 +243,46 @@ public void GetApiDescription_PopulatesParametersThatAppearOnRouteTemplate_AndHa
         }
     }
 
+    [Theory]
+    [InlineData("api/products/{id}", nameof(BindingSource.Path), true)]
+    [InlineData("api/products", nameof(BindingSource.Path), false)]
+    [InlineData("api/products", nameof(BindingSource.Body), true)]
+    [InlineData("api/products", nameof(BindingSource.Query), true)]
+    public void GetApiDescription_WithInferredBindingSource(
+        string template,
+        string inferredBindingSourceName,
+        bool inferredParameterShouldBeIncluded)
+    {
+        // Arrange
+        var action = CreateActionDescriptor(nameof(FromModelBinding));
+        action.AttributeRouteInfo = new AttributeRouteInfo { Template = template };
+
+        foreach (var actionParameter in action.Parameters)
+        {
+            actionParameter.BindingInfo = new BindingInfo()
+            {
+                BindingSource = new BindingSource(inferredBindingSourceName, displayName: null, isGreedy: false, isFromRequest: true)
+            };
+        }
+
+        var expectedBindingSource = new BindingSource(inferredBindingSourceName, displayName: null, isGreedy: false, isFromRequest: true);
+
+        // Act
+        var descriptions = GetApiDescriptions(action);
+
+        // Assert
+        var description = Assert.Single(descriptions);
+
+        Assert.Equal(inferredParameterShouldBeIncluded, description.ParameterDescriptions.Count == 1);
+
+        if (inferredParameterShouldBeIncluded)
+        {
+            var parameter = Assert.Single(description.ParameterDescriptions);
+            Assert.Equal(expectedBindingSource, parameter.Source);
+            Assert.Equal("id", parameter.Name);
+        }
+    }
+
     [Fact]
     public void GetApiDescription_ParameterDescription_IncludesParameterDescriptor()
     {