Set workspace baseUrl when creating a workspace

src/Microsoft.OpenApi/Reader/OpenApiJsonReader.cs

@@ -192,7 +192,8 @@ private JsonNode LoadJsonNodes(TextReader input)
         private async Task<OpenApiDiagnostic> LoadExternalRefs(OpenApiDocument document, CancellationToken cancellationToken, OpenApiReaderSettings settings, string format = null)
         {
             // Create workspace for all documents to live in.
-            var openApiWorkSpace = new OpenApiWorkspace();
+            var baseUrl = settings.BaseUrl ?? new Uri(OpenApiConstants.BaseRegistryUri);
+            var openApiWorkSpace = new OpenApiWorkspace(baseUrl);
 
             // Load this root document into the workspace
             var streamLoader = new DefaultStreamLoader(settings.BaseUrl);

src/Microsoft.OpenApi/Reader/Services/DefaultStreamLoader.cs

@@ -56,7 +56,16 @@
         /// <exception cref="ArgumentException"></exception>
         public async Task<Stream> LoadAsync(Uri uri)
         {
-            var absoluteUri = new Uri(baseUrl, uri);
+            Uri absoluteUri;
+            if (baseUrl.Equals(OpenApiConstants.BaseRegistryUri))
+            {
+                // use current working directory
+                absoluteUri = new Uri(Directory.GetCurrentDirectory() + uri);
+            }
+            else
+            {
+                absoluteUri = new Uri(baseUrl, uri);
+            }
 
             switch (absoluteUri.Scheme)
             {