getDocCommentTemplateAtPosition: Return result if in empty comment (microsoft#26026)

Author: Andy

src/services/jsDoc.ts

@@ -272,14 +272,16 @@ namespace ts.JsDoc {
      */
 
     export function getDocCommentTemplateAtPosition(newLine: string, sourceFile: SourceFile, position: number): TextInsertion | undefined {
-        // Check if in a context where we don't want to perform any insertion
-        if (isInString(sourceFile, position) || isInComment(sourceFile, position) || hasDocComment(sourceFile, position)) {
+        const tokenAtPos = getTokenAtPosition(sourceFile, position);
+        const existingDocComment = findAncestor(tokenAtPos, isJSDoc);
+        if (existingDocComment && (existingDocComment.comment !== undefined || length(existingDocComment.tags))) {
+            // Non-empty comment already exists.
             return undefined;
         }
 
-        const tokenAtPos = getTokenAtPosition(sourceFile, position);
         const tokenStart = tokenAtPos.getStart(sourceFile);
-        if (!tokenAtPos || tokenStart < position) {
+        // Don't provide a doc comment template based on a *previous* node. (But an existing empty jsdoc comment will likely start before `position`.)
+        if (!existingDocComment && tokenStart < position) {
             return undefined;
         }
 

tests/cases/fourslash/docCommentTemplate_insideEmptyComment.ts

@@ -0,0 +1,15 @@
+/// <reference path='fourslash.ts' />
+
+/////** /**/ */
+////function f(p) { return p; }
+////
+/////** Doc/*1*/ */
+////function g(p) { return p; }
+
+verify.docCommentTemplateAt("", /*newTextOffset*/ 8,
+`/**
+ * 
+ * @param p
+ */`);
+
+verify.noDocCommentTemplateAt("1");