fix: incremental insertion incorrect if input at block start (#3743)

Co-authored-by: Johnson Chu <[email protected]>

packages/language-core/src/plugins/file-vue.ts

@@ -22,16 +22,23 @@ const plugin: VueLanguagePlugin = (_ctx) => {
 			].filter((block): block is NonNullable<typeof block> => !!block);
 
 			const hitBlock = blocks.find(block => change.start >= block.loc.start.offset && change.end <= block.loc.end.offset);
-
 			if (!hitBlock) {
 				return;
 			}
 
-			hitBlock.content =
+			const oldContent = hitBlock.content;
+			const newContent = hitBlock.content =
 				hitBlock.content.substring(0, change.start - hitBlock.loc.start.offset)
 				+ change.newText
 				+ hitBlock.content.substring(change.end - hitBlock.loc.start.offset);
 
+			// #3449
+			const endTagRegex = new RegExp(`</\\s*${hitBlock.type}\\s*>`);
+			const insertedEndTag = !!oldContent.match(endTagRegex) !== !!newContent.match(endTagRegex);
+			if (insertedEndTag) {
+				return;
+			}
+
 			const lengthDiff = change.newText.length - (change.end - change.start);
 
 			for (const block of blocks) {