feat(47223): show completion in jsdoc template tag (microsoft#47317)

Author: a-tarasyuk

src/services/completions.ts

@@ -1770,14 +1770,15 @@ namespace ts.Completions {
                 if (tag.tagName.pos <= position && position <= tag.tagName.end) {
                     return { kind: CompletionDataKind.JsDocTagName };
                 }
-                if (isTagWithTypeExpression(tag) && tag.typeExpression && tag.typeExpression.kind === SyntaxKind.JSDocTypeExpression) {
+                const typeExpression = tryGetTypeExpressionFromTag(tag);
+                if (typeExpression) {
                     currentToken = getTokenAtPosition(sourceFile, position);
                     if (!currentToken ||
                         (!isDeclarationName(currentToken) &&
                             (currentToken.parent.kind !== SyntaxKind.JSDocPropertyTag ||
                                 (currentToken.parent as JSDocPropertyTag).name !== currentToken))) {
                         // Use as type location if inside tag's type expression
-                        insideJsDocTagTypeExpression = isCurrentlyEditingNode(tag.typeExpression);
+                        insideJsDocTagTypeExpression = isCurrentlyEditingNode(typeExpression);
                     }
                 }
                 if (!insideJsDocTagTypeExpression && isJSDocParameterTag(tag) && (nodeIsMissing(tag.name) || tag.name.pos <= position && position <= tag.name.end)) {
@@ -2046,7 +2047,7 @@ namespace ts.Completions {
             hasUnresolvedAutoImports,
         };
 
-        type JSDocTagWithTypeExpression = JSDocParameterTag | JSDocPropertyTag | JSDocReturnTag | JSDocTypeTag | JSDocTypedefTag;
+        type JSDocTagWithTypeExpression = JSDocParameterTag | JSDocPropertyTag | JSDocReturnTag | JSDocTypeTag | JSDocTypedefTag | JSDocTemplateTag;
 
         function isTagWithTypeExpression(tag: JSDocTag): tag is JSDocTagWithTypeExpression {
             switch (tag.kind) {
@@ -2056,11 +2057,21 @@ namespace ts.Completions {
                 case SyntaxKind.JSDocTypeTag:
                 case SyntaxKind.JSDocTypedefTag:
                     return true;
+                case SyntaxKind.JSDocTemplateTag:
+                    return !!(tag as JSDocTemplateTag).constraint;
                 default:
                     return false;
             }
         }
 
+        function tryGetTypeExpressionFromTag(tag: JSDocTag): JSDocTypeExpression | undefined {
+            if (isTagWithTypeExpression(tag)) {
+                const typeExpression = isJSDocTemplateTag(tag) ? tag.constraint : tag.typeExpression;
+                return typeExpression && typeExpression.kind === SyntaxKind.JSDocTypeExpression ? typeExpression : undefined;
+            }
+            return undefined;
+        }
+
         function getTypeScriptMemberSymbols(): void {
             // Right of dot member completion list
             completionKind = CompletionKind.PropertyAccess;

tests/cases/fourslash/jsdocTemplateTagCompletion.ts

@@ -0,0 +1,11 @@
+///<reference path="fourslash.ts" />
+
+/////**
+//// * @template {/**/} T
+//// * @typedef {Object} Foo
+//// * @property {T} foo
+//// */
+
+verify.completions(
+    { marker: "", exact: completion.globalTypes },
+);