fix: base url should be read from the settings when available

Author: baywet

src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs

@@ -241,11 +241,10 @@ private static async Task<ReadResult> InternalLoadAsync(Stream input, string for
         {
             settings ??= DefaultReaderSettings.Value;
             var reader = settings.GetReader(format);
-            var location = new Uri(OpenApiConstants.BaseRegistryUri);
-            if (input is FileStream fileStream)
-            {
-                location = new Uri(fileStream.Name);
-            }
+            var location =
+                        settings.BaseUrl ??
+                        (input is FileStream fileStream ? new Uri(fileStream.Name) : null) ??
+                        new Uri(OpenApiConstants.BaseRegistryUri);
 
             var readResult = await reader.ReadAsync(input, location, settings, cancellationToken).ConfigureAwait(false);
 
@@ -290,7 +289,7 @@ private static ReadResult InternalLoad(MemoryStream input, string format, OpenAp
             return readResult;
         }
 
-      private static async Task<(Stream, string?)> RetrieveStreamAndFormatAsync(string url, OpenApiReaderSettings settings, CancellationToken token = default)
+        private static async Task<(Stream, string?)> RetrieveStreamAndFormatAsync(string url, OpenApiReaderSettings settings, CancellationToken token = default)
         {
             if (string.IsNullOrEmpty(url))
             {
@@ -308,8 +307,8 @@ private static ReadResult InternalLoad(MemoryStream input, string format, OpenAp
                     var mediaType = response.Content.Headers.ContentType?.MediaType;
                     var contentType = mediaType?.Split(";".ToCharArray(), StringSplitOptions.RemoveEmptyEntries)[0];
                     format = contentType?.Split('/').Last().Split('+').Last().Split('-').Last();
-                    
-                  // for non-standard MIME types e.g. text/x-yaml used in older libs or apps
+
+                    // for non-standard MIME types e.g. text/x-yaml used in older libs or apps
 #if NETSTANDARD2_0
                     stream = await response.Content.ReadAsStreamAsync();
 #else

test/Microsoft.OpenApi.Tests/Reader/OpenApiModelFactoryTests.cs

@@ -0,0 +1,122 @@
+using Xunit;
+using Microsoft.OpenApi.Reader;
+using Microsoft.OpenApi.Models;
+using System.Threading.Tasks;
+using System.IO;
+using System;
+
+namespace Microsoft.OpenApi.Tests.Reader;
+
+public class OpenApiModelFactoryTests
+{
+    [Fact]
+    public async Task UsesSettingsBaseUrl()
+    {
+        var tempFilePathReferee = Path.Combine(Path.GetTempPath(), Path.GetTempFileName());
+        await File.WriteAllTextAsync(tempFilePathReferee,
+"""
+{
+    "openapi": "3.1.1",
+    "info": {
+        "title": "OData Service for namespace microsoft.graph",
+        "description": "This OData service is located at https://graph.microsoft.com/v1.0",
+        "version": "1.0.1"
+    },
+    "servers": [
+        {
+            "url": "https://graph.microsoft.com/v1.0"
+        }
+    ],
+    "paths": {
+        "/placeholder": {
+            "get": {
+                "responses": {
+                    "200": {
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "type": "string"
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "MySchema": {
+                "type": "object",
+                "properties": {
+                    "id": {
+                        "type": "string"
+                    }
+                }
+            }
+        }
+    }
+}
+""");
+        var tempFilePathReferrer = Path.Combine(Path.GetTempPath(), Path.GetTempFileName());
+        await File.WriteAllTextAsync(tempFilePathReferrer,
+$$$"""
+{
+    "openapi": "3.1.1",
+    "info": {
+        "title": "OData Service for namespace microsoft.graph",
+        "description": "This OData service is located at https://graph.microsoft.com/v1.0",
+        "version": "1.0.1"
+    },
+    "servers": [
+        {
+            "url": "https://graph.microsoft.com/v1.0"
+        }
+    ],
+    "paths": {
+        "/placeholder": {
+            "get": {
+                "responses": {
+                    "200": {
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "./{{{Path.GetFileName(tempFilePathReferee)}}}#/components/schemas/MySchema"
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "MySchema": {
+                "type": "object",
+                "properties": {
+                    "id": {
+                        "type": "string"
+                    }
+                }
+            }
+        }
+    }
+}
+""");
+        // read referrer document to a memory stream
+        using var stream = new MemoryStream();
+        using var reader = new StreamReader(tempFilePathReferrer);
+        await reader.BaseStream.CopyToAsync(stream);
+        stream.Position = 0;
+        var baseUri = new Uri(tempFilePathReferrer);
+        var settings = new OpenApiReaderSettings
+        {
+            BaseUrl = baseUri, 
+        };
+        var readResult = await OpenApiDocument.LoadAsync(stream, settings: settings);
+        Assert.NotNull(readResult.Document);
+        Assert.NotNull(readResult.Document.Components);
+        Assert.Equal(baseUri, readResult.Document.BaseUri);
+    }
+}