Improve handling of singular strings in plural-form batches

When batches contain both singular and plural entries, the AI
sometimes returns `<f0>...<fN>` form tags for singular strings
(e.g., "30 files"). The parser accepted all forms, and the
post-validator blanked them for placeholder mismatches.

- Clarify prompt to show both formats when batch has mixed entries
- Extract only f0 when AI returns form tags for singular entries
- Initialize singular entries with 1 msgstr slot instead of pluralCount

Author: mrcasual

src/utils/xmlTranslation.js

@@ -75,11 +75,12 @@ export function buildXmlPrompt(batch, targetLang, pluralCount, dictionaryMatches
 	prompt += xmlTags + '\n\nRespond:\n';
 
 	if (hasPlurals) {
-		prompt += `For entries with <singular> and <plural> tags, provide ${pluralCount} translations:\n\n`;
-
 		const formTags = Array.from({ length: pluralCount }, (_, i) => `<f${i}>translation for form ${i}</f${i}>`).join('');
 
-		prompt += `Format: <t i="N">${formTags}</t>\n`;
+		prompt += `For entries with <singular> and <plural> tags, provide ${pluralCount} plural forms:\n`;
+		prompt += `Format: <t i="N">${formTags}</t>\n\n`;
+		prompt += `For all other entries (no <singular>/<plural>), provide a single translation:\n`;
+		prompt += `Format: <t i="N">translation</t>\n`;
 	} else {
 		prompt += `Format: <t i="N">translation</t>\n`;
 	}
@@ -200,7 +201,7 @@ function validatePluralForms(forms, originalMsgid, expectedCount, itemId, logger
 export function parseXmlResponse(xmlResponse, batch, pluralCount, logger, dictionaryCount = 0, verbosityLevel = 1) {
 	const result = batch.map((entry) => ({
 		msgid: entry.msgid,
-		msgstr: Array(pluralCount).fill(''),
+		msgstr: Array(entry.msgid_plural ? pluralCount : 1).fill(''),
 	}));
 
 	const validationStats = createEmptyValidationStats();
@@ -249,8 +250,9 @@ export function parseXmlResponse(xmlResponse, batch, pluralCount, logger, dictio
 			}
 
 			const hasFormTags = block.includes('<f0>');
+			const isSingularEntry = !batch[batchIndex].msgid_plural;
 
-			if (hasFormTags) {
+			if (hasFormTags && !isSingularEntry) {
 				const forms = [];
 
 				for (let i = 0; i < pluralCount; i++) {
@@ -278,6 +280,17 @@ export function parseXmlResponse(xmlResponse, batch, pluralCount, logger, dictio
 				}
 
 				result[batchIndex].msgstr = correctedForms;
+			} else if (hasFormTags && isSingularEntry) {
+				// AI incorrectly returned plural forms for a singular entry.
+				// Extract only form 0 and discard the rest.
+				const formRegex = /<f0>(.*?)<\/f0>/s;
+				const formMatch = block.match(formRegex);
+
+				if (formMatch) {
+					const translation = normalizeNbsp(decodeXmlEntities(formMatch[1]), batch[batchIndex].msgid);
+
+					result[batchIndex].msgstr = [translation];
+				}
 			} else {
 				const contentMatch = block.match(/<t[^>]*>(.*?)<\/t>/s);
 

tests/integration/openai-with-dictionary.test.js

@@ -223,7 +223,7 @@ describe('OpenAI Provider with Dictionary Integration', () => {
 		expect(promptMessage).toContain('<source i="1" placeholders="none">item</source>');
 		expect(promptMessage).toContain('<singular>One item</singular>');
 		expect(promptMessage).toContain('<plural>%d items</plural>');
-		expect(promptMessage).toContain('For entries with <singular> and <plural> tags, provide 2 translations');
+		expect(promptMessage).toContain('For entries with <singular> and <plural> tags, provide 2 plural forms');
 	});
 
 	it('should handle API errors gracefully with dictionary', async () => {

tests/unit/placeholderValidation.test.js

@@ -539,4 +539,36 @@ describe('placeholder validation', () => {
 			expect(translations[0].msgstr[0]).toBe('لا عناصر');
 		});
 	});
+
+	describe('singular entries with form tags', () => {
+		it('should extract only f0 when AI returns plural forms for a singular entry', () => {
+			// AI incorrectly returns <f0>...<f5> for a singular string like "30 files".
+			const batch = [{ msgid: '30 files' }];
+			const forms = ['30 ملفًا', '30 ملف', '30 ملفان', '%d ملفات', '%d ملفًا', '%d ملف'];
+			const { translations } = parseXmlResponse(xml([forms]), batch, 6, mockLogger);
+
+			expect(translations[0].msgstr).toHaveLength(1);
+			expect(translations[0].msgstr[0]).toBe('30 ملفًا');
+		});
+
+		it('should initialize singular entries with 1 msgstr slot', () => {
+			const batch = [{ msgid: 'Hello' }, { msgid: 'One item', msgid_plural: '%d items' }];
+			const { translations } = parseXmlResponse('', batch, 6, mockLogger);
+
+			expect(translations[0].msgstr).toHaveLength(1);
+			expect(translations[1].msgstr).toHaveLength(6);
+		});
+
+		it('should not trigger placeholder warnings for discarded plural forms', () => {
+			const { logger, warnings } = createSpyLogger();
+			const batch = [{ msgid: '30 files' }];
+			// AI adds %d in forms 3-5 — these should be discarded, not warned about.
+			const forms = ['30 ملفًا', '30 ملف', '30 ملفان', '%d ملفات', '%d ملفًا', '%d ملف'];
+			parseXmlResponse(xml([forms]), batch, 6, logger);
+
+			const placeholderWarnings = warnings.filter((w) => w.includes('Placeholder mismatch'));
+
+			expect(placeholderWarnings).toHaveLength(0);
+		});
+	});
 });

tests/unit/xmlTranslationWithDictionary.test.js

@@ -59,7 +59,7 @@ describe('XML Translation with Dictionary', () => {
 			expect(result.xmlPrompt).toContain('<source i="1" placeholders="none">item</source>');
 			expect(result.xmlPrompt).toContain('<singular>One item</singular>');
 			expect(result.xmlPrompt).toContain('<plural>%d items</plural>');
-			expect(result.xmlPrompt).toContain('For entries with <singular> and <plural> tags, provide 2 translations');
+			expect(result.xmlPrompt).toContain('For entries with <singular> and <plural> tags, provide 2 plural forms');
 		});
 
 		it('should escape XML in dictionary terms', () => {