feat: add Formality options PreferLess and PreferMore

CHANGELOG.md

@@ -5,7 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
-# [Unreleased]
+## [Unreleased]
+### Added
+* Add new `Formality` options: `PreferLess` and `PreferMore`.
 ### Changed
 * Requests resulting in `503 Service Unavailable` errors are now retried.
   Attempting to download a document before translation is completed will now

DeepL/Formality.cs

@@ -12,6 +12,12 @@ public enum Formality {
     Less,
 
     /// <summary>Increased formality.</summary>
-    More
+    More,
+
+    /// <summary>Less formality, i.e. more informal, if available for the specified target language, otherwise default.</summary>
+    PreferLess,
+
+    /// <summary>Increased formality, if available for the specified target language, otherwise default.</summary>
+    PreferMore
   }
 }

DeepL/Translator.cs

@@ -882,8 +882,23 @@ await _client.ApiGetAsync("/v2/languages", cancellationToken, queryParams)
         bodyParams.Add(("glossary_id", options.GlossaryId));
       }
 
-      if (options.Formality != Formality.Default) {
-        bodyParams.Add(("formality", options.Formality.ToString().ToLowerInvariant()));
+      switch (options.Formality) {
+        case Formality.Default:
+          break;
+        case Formality.Less:
+          bodyParams.Add(("formality", "less"));
+          break;
+        case Formality.More:
+          bodyParams.Add(("formality", "more"));
+          break;
+        case Formality.PreferLess:
+          bodyParams.Add(("formality", "prefer_less"));
+          break;
+        case Formality.PreferMore:
+          bodyParams.Add(("formality", "prefer_more"));
+          break;
+        default:
+          throw new ArgumentException($"{nameof(options.Formality)} value is out of range");
       }
 
       if (options.SentenceSplittingMode != SentenceSplittingMode.All) {

DeepLTests/TranslateTextTest.cs

@@ -132,6 +132,24 @@ public async Task TestFormality() {
       if (!IsMockServer) {
         Assert.Equal("Wie geht es Ihnen?", result.Text);
       }
+
+      result = await translator.TranslateTextAsync(
+            "How are you?",
+            null,
+            "DE",
+            new TextTranslateOptions { Formality = Formality.PreferMore });
+      if (!IsMockServer) {
+        Assert.Equal("Wie geht es Ihnen?", result.Text);
+      }
+
+      result = await translator.TranslateTextAsync(
+            "How are you?",
+            null,
+            "DE",
+            new TextTranslateOptions { Formality = Formality.PreferLess });
+      if (!IsMockServer) {
+        Assert.Equal("Wie geht es dir?", result.Text);
+      }
     }
 
     [Fact]