revert: lower-case formality and splitSentences values again

The API rejects formality and split_sentences values that are not lower
case, so sending them as given turned values such as 'Less' that worked
before into HTTP 400 errors. Restore the lower-casing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: hive-bot

CHANGELOG.md

@@ -293,10 +293,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `updateMultilingualGlossary()`, `updateMultilingualGlossaryDictionary()` and
   `replaceMultilingualGlossaryDictionary()`, so `' foo '` is sent as `'foo'` and
   a whitespace-only term throws a `DeepLError` before any request.
-- The `formality` option of text and document translation is sent as given,
-  no longer lower-cased.
-- A `splitSentences` value other than the aliases `'on'`, `'default'` and
-  `'off'` is sent as given, no longer lower-cased.
 - `getUsage()` leaves `character`, `document` and `teamDocument` undefined
   when the response's count or limit for them is not a number, as it already did
   for the API Pro usage fields. Before, a `null` or string value was returned as

README.md

@@ -176,9 +176,6 @@ console.log(await deeplClient.translateText('How are you?', null, 'de', { formal
     -   `'nonewlines'`: input text will be split into sentences using punctuation
         but not newlines.
     -   `'on'` and `'default'` are deprecated aliases of `'1'`.
-
-    The aliases `'on'`, `'default'` and `'off'` match in any letter case; any
-    other value is sent exactly as given.
 -   `preserveFormatting`: controls automatic-formatting-correction. Set to `true`
     to prevent automatic-correction of formatting, default: `false`.
 -   `formality`: controls whether translations should lean toward informal or
@@ -191,8 +188,6 @@ console.log(await deeplClient.translateText('How are you?', null, 'de', { formal
     - `'default'`: use default formality.
     - `'prefer_less'`: use informal language if available, otherwise default.
     - `'prefer_more'`: use formal, more polite language if available, otherwise default.
-
-    The value is sent exactly as given, without changing its letter case.
 -   `glossary`: specifies a glossary to use with translation, either as a string
     containing the glossary ID, or a `MultilingualGlossaryInfo`/`GlossaryInfo` as returned by
     `getMultilingualGlossary()`/`getGlossary()`.

src/types.ts

@@ -184,18 +184,14 @@ export interface TranslateTextOptions extends BaseRequestOptions {
      *   for applications where each input translation text is only one sentence.
      * - 'nonewlines': Input translation text will be split into sentences using only punctuation
      *   but not newlines.
-     * The aliases 'on', 'default' and 'off' match in any letter case; any other value is sent as
-     * given.
      */
     splitSentences?: SentenceSplittingMode;
 
     /** Set to true to prevent the translation engine from correcting some formatting aspects, and
      * instead leave the formatting unchanged, default is false. */
     preserveFormatting?: boolean;
 
-    /**
-     * Controls whether translations should lean toward formal or informal language. Sent as given.
-     */
+    /** Controls whether translations should lean toward formal or informal language. */
     formality?: Formality;
 
     /** Specifies the ID of a glossary to use with translation. Or
@@ -281,9 +277,7 @@ export interface TranslateTextOptions extends BaseRequestOptions {
  * Options that can be specified when translating documents.
  */
 export interface DocumentTranslateOptions extends BaseRequestOptions {
-    /**
-     * Controls whether translations should lean toward formal or informal language. Sent as given.
-     */
+    /** Controls whether translations should lean toward formal or informal language. */
     formality?: Formality;
 
     /** Specifies the ID of a glossary to use with translation. Or

src/utils.ts

@@ -249,7 +249,8 @@ export function buildURLSearchParams(
         searchParams.append('source_lang', sourceLang);
     }
     if (formality !== undefined) {
-        searchParams.append('formality', String(formality));
+        const formalityStr = String(formality).toLowerCase();
+        searchParams.append('formality', formalityStr);
     }
     if (glossary !== undefined) {
         if (!isString(glossary)) {
@@ -407,13 +408,13 @@ export function validateAndAppendTextOptions(
         return;
     }
     if (options.splitSentences !== undefined) {
-        const alias = options.splitSentences.toLowerCase();
-        if (alias === 'on' || alias === 'default') {
+        const splitSentences = options.splitSentences.toLowerCase();
+        if (splitSentences === 'on' || splitSentences === 'default') {
             data.append('split_sentences', '1');
-        } else if (alias === 'off') {
+        } else if (splitSentences === 'off') {
             data.append('split_sentences', '0');
         } else {
-            data.append('split_sentences', options.splitSentences);
+            data.append('split_sentences', splitSentences);
         }
     }
     if (options.preserveFormatting !== undefined) {

tests/offline/translateText.test.ts

@@ -109,6 +109,7 @@ describe('Translator.translateText', () => {
         ['prefer_less', 'prefer_less'],
         ['prefer_more', 'prefer_more'],
         ['default', 'default'],
+        ['MORE', 'more'],
     ])('sends formality %s as %s', async (formality, sent) => {
         expectTranslateBody({ ...baseBody, formality: sent });
 
@@ -117,14 +118,6 @@ describe('Translator.translateText', () => {
         });
     });
 
-    it('sends formality as given, without lower-casing it', async () => {
-        expectTranslateBody({ ...baseBody, formality: 'MORE' });
-
-        await makeTranslator().translateText('abc', null, 'de', {
-            formality: <deepl.Formality>'MORE',
-        });
-    });
-
     it.each([
         ['on', '1'],
         ['default', '1'],
@@ -141,14 +134,6 @@ describe('Translator.translateText', () => {
         });
     });
 
-    it('sends a splitSentences value other than an alias as given, without lower-casing it', async () => {
-        expectTranslateBody({ ...baseBody, split_sentences: 'NoNewlines' });
-
-        await makeTranslator().translateText('abc', null, 'de', {
-            splitSentences: <deepl.SentenceSplittingMode>'NoNewlines',
-        });
-    });
-
     it('does not change the splitSentences value of the caller options', async () => {
         expectTranslateBody({ ...baseBody, split_sentences: '0' });
         const options: deepl.TranslateTextOptions = { splitSentences: 'OFF' };