Close remaining final-review gaps

Root cause: the provider-modernization branch still had a small set of follow-up inconsistencies around nullable annotations, Bing response handling, and the shared HttpClient test helper after the larger transport and serializer refactors.

Author: niemyjski

AGENTS.md

@@ -132,6 +132,7 @@ Before marking work complete, verify:
 - **xUnit** as the primary testing framework
 - Tests cover all providers with shared base patterns (`GeocoderTest`, `AsyncGeocoderTest`)
 - Provider-specific tests extend base test classes
+- For `HttpClient` failure-path tests, prefer `TestHttpMessageHandler.CreateResponse(...)` or `CreateResponseAsync(...)` instead of constructing `HttpResponseMessage` inline inside handler lambdas
 
 ### Running Tests
 

src/Geocoding.Core/Extensions.cs

@@ -27,7 +27,7 @@ public static bool IsNullOrEmpty<T>([NotNullWhen(false)] this ICollection<T>? co
     /// <typeparam name="T">The enumerable item type.</typeparam>
     /// <param name="self">The source enumerable.</param>
     /// <param name="actor">The action to execute for each item.</param>
-    public static void ForEach<T>(this IEnumerable<T> self, Action<T> actor)
+    public static void ForEach<T>(this IEnumerable<T>? self, Action<T> actor)
     {
         if (actor is null)
             throw new ArgumentNullException(nameof(actor));
@@ -66,7 +66,7 @@ private static JsonSerializerOptions CreateJsonOptions()
     /// </summary>
     /// <param name="o">The object to serialize.</param>
     /// <returns>The JSON payload, or an empty string when the input is null.</returns>
-    public static string ToJSON(this object o)
+    public static string ToJSON(this object? o)
     {
         if (o is null)
             return String.Empty;

src/Geocoding.MapQuest/MapQuestGeocoder.cs

@@ -49,14 +49,11 @@ public MapQuestGeocoder(string key)
 
     private IEnumerable<Address> HandleSingleResponse(MapQuestResponse res)
     {
-        if (res is not null && !res.Results.IsNullOrEmpty())
-        {
-            return HandleSingleResponse(from r in res.Results.OfType<MapQuestResult>()
-                                        from l in r.Locations?.OfType<MapQuestLocation>() ?? Enumerable.Empty<MapQuestLocation>()
-                                        select l);
-        }
-        else
-            return Array.Empty<Address>();
+        return res is not null && !res.Results.IsNullOrEmpty()
+            ? HandleSingleResponse(from r in res.Results.OfType<MapQuestResult>()
+                                   from l in r.Locations?.OfType<MapQuestLocation>() ?? Enumerable.Empty<MapQuestLocation>()
+                                   select l)
+            : Array.Empty<Address>();
     }
 
     private IEnumerable<Address> HandleSingleResponse(IEnumerable<MapQuestLocation> locs)

src/Geocoding.Microsoft/BingMapsGeocoder.cs

@@ -75,7 +75,7 @@ private string GetQueryUrl(string address)
         first = AppendParameter(parameters, address, Query, first);
         first = AppendGlobalParameters(parameters, first);
 
-        return String.Format(FormattedQuery, parameters.ToString(), _bingKey);
+        return String.Format(FormattedQuery, parameters, _bingKey);
     }
 
     private string GetQueryUrl(string street, string city, string state, string postalCode, string country)
@@ -89,7 +89,7 @@ private string GetQueryUrl(string street, string city, string state, string post
         first = AppendParameter(parameters, street, Address, first);
         first = AppendGlobalParameters(parameters, first);
 
-        return String.Format(FormattedQuery, parameters.ToString(), _bingKey);
+        return String.Format(FormattedQuery, parameters, _bingKey);
     }
 
     private string GetQueryUrl(double latitude, double longitude)
@@ -249,15 +249,11 @@ protected virtual IEnumerable<BingAddress> ParseResponse(Json.Response response)
             if (resourceSet is null)
                 continue;
 
-            var locations = resourceSet.Locations;
-            if (locations.IsNullOrEmpty())
-                continue;
-
-            foreach (var location in locations.Where(location => location?.Point?.Coordinates is { Length: >= 2 }
+            foreach (var location in resourceSet.Resources.OfType<Json.Location>().Where(location => location.Point?.Coordinates is { Length: >= 2 }
                 && location.Address is not null
                 && !String.IsNullOrWhiteSpace(location.Address.FormattedAddress)))
             {
-                var coordinates = location!.Point!.Coordinates!;
+                var coordinates = location.Point!.Coordinates!;
 
                 if (!Enum.TryParse(location.EntityType, out EntityType entityType))
                     entityType = EntityType.Unknown;
@@ -309,8 +305,8 @@ protected virtual HttpClient BuildClient()
 
             if (!response.IsSuccessStatusCode)
             {
-                var body = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
-                throw new BingGeocodingException(new HttpRequestException($"Bing Maps request failed ({(int)response.StatusCode} {response.ReasonPhrase}).{BuildResponsePreview(body)}"));
+                var preview = await BuildResponsePreviewAsync(response.Content).ConfigureAwait(false);
+                throw new BingGeocodingException(new HttpRequestException($"Bing Maps request failed ({(int)response.StatusCode} {response.ReasonPhrase}).{preview}"));
             }
 
             using (var stream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
@@ -335,16 +331,21 @@ private ConfidenceLevel EvaluateConfidence(string? confidence)
         return ConfidenceLevel.Unknown;
     }
 
-    private static string BuildResponsePreview(string? body)
+    private static async Task<string> BuildResponsePreviewAsync(HttpContent content)
     {
-        if (String.IsNullOrWhiteSpace(body))
+        using var stream = await content.ReadAsStreamAsync().ConfigureAwait(false);
+        using var reader = new StreamReader(stream, Encoding.UTF8, detectEncodingFromByteOrderMarks: true, bufferSize: 1024, leaveOpen: false);
+        var buffer = new char[256];
+        int read = await reader.ReadBlockAsync(buffer, 0, buffer.Length).ConfigureAwait(false);
+
+        if (read == 0)
             return String.Empty;
 
-        var preview = body!.Trim();
-        if (preview.Length > 256)
-            preview = preview.Substring(0, 256) + "...";
+        var preview = new string(buffer, 0, read).Trim();
+        if (String.IsNullOrWhiteSpace(preview))
+            return String.Empty;
 
-        return " Response preview: " + preview;
+        return " Response preview: " + preview + (reader.EndOfStream ? String.Empty : "...");
     }
 
     private string BingUrlEncode(string toEncode)

test/Geocoding.Tests/TestHttpMessageHandler.cs

@@ -18,12 +18,17 @@ protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage reques
         return _sendAsync(request, cancellationToken);
     }
 
-    public static Task<HttpResponseMessage> CreateResponseAsync(HttpStatusCode statusCode, string? reasonPhrase = null, string? body = null)
+    public static HttpResponseMessage CreateResponse(HttpStatusCode statusCode, string? reasonPhrase = null, string? body = null)
     {
-        return Task.FromResult(new HttpResponseMessage(statusCode)
+        return new HttpResponseMessage(statusCode)
         {
             ReasonPhrase = reasonPhrase,
             Content = String.IsNullOrWhiteSpace(body) ? null : new StringContent(body, Encoding.UTF8, "text/plain")
-        });
+        };
+    }
+
+    public static Task<HttpResponseMessage> CreateResponseAsync(HttpStatusCode statusCode, string? reasonPhrase = null, string? body = null)
+    {
+        return Task.FromResult(CreateResponse(statusCode, reasonPhrase, body));
     }
 }