fix: clamp completion range for unclosed string literals (#239)

When an attribute value has an unclosed quote, the replace range could
extend past `<` characters after the cursor, causing completions to
delete subsequent HTML tags. Clamp valueContentEnd to the cursor offset
when the closing quote is missing.

Fixes microsoft/vscode#273226

Author: maruthang

src/services/htmlCompletion.ts

@@ -294,6 +294,10 @@ export class HTMLCompletion {
 				// valueEnd points to the char after quote, which encloses the replace range
 				if (valueEnd > valueStart && text[valueEnd - 1] === text[valueStart]) {
 					valueContentEnd--;
+				} else {
+					// unclosed quote: clamp the end to the cursor position so that
+					// the replace range does not extend into subsequent HTML content
+					valueContentEnd = offset;
 				}
 
 				const wsBefore = getWordStart(text, offset, valueContentStart);

src/test/completion.test.ts

@@ -164,6 +164,15 @@ suite('HTML Completion', () => {
 		testCompletionFor('<input src="c" type=color| ', {
 			items: [{ label: 'color', resultText: '<input src="c" type="color" ' }]
 		});
+
+		// unclosed string literals should not extend the replace range past the cursor
+		testCompletionFor('<th><input type="che|</th>', {
+			items: [{ label: 'checkbox', resultText: '<th><input type="checkbox</th>' }]
+		});
+		testCompletionFor('<th><input type="che|</th><td></td>', {
+			items: [{ label: 'checkbox', resultText: '<th><input type="checkbox</th><td></td>' }]
+		});
+
 		testCompletionFor('<div dir=|></div>', {
 			items: [
 				{ label: 'ltr', resultText: '<div dir="ltr"></div>' },