Collect jsdoc tags for type parameters (#26824)

Before the template tag, there was no reason to do this, but now you can
add JSDoc for type parameters in Typescript.

Author: sandersn

Diff for: src/compiler/utilities.ts

@@ -2116,6 +2116,10 @@ namespace ts {
                 result = addRange(result, getJSDocParameterTags(node as ParameterDeclaration));
                 break;
             }
+            if (node.kind === SyntaxKind.TypeParameter) {
+                result = addRange(result, getJSDocTypeParameterTags(node as TypeParameterDeclaration));
+                break;
+            }
             node = getNextJSDocCommentLocation(node);
         }
         return result || emptyArray;
@@ -4994,15 +4998,14 @@ namespace ts {
     /**
      * Gets the JSDoc parameter tags for the node if present.
      *
-     * @remarks Returns any JSDoc param tag that matches the provided
+     * @remarks Returns any JSDoc param tag whose name matches the provided
      * parameter, whether a param tag on a containing function
      * expression, or a param tag on a variable declaration whose
      * initializer is the containing function. The tags closest to the
      * node are returned first, so in the previous example, the param
      * tag on the containing function expression would be first.
      *
-     * Does not return tags for binding patterns, because JSDoc matches
-     * parameters by name and binding patterns do not have a name.
+     * For binding patterns, parameter tags are matched by position.
      */
     export function getJSDocParameterTags(param: ParameterDeclaration): ReadonlyArray<JSDocParameterTag> {
         if (param.name) {
@@ -5023,6 +5026,22 @@ namespace ts {
         return emptyArray;
     }
 
+    /**
+     * Gets the JSDoc type parameter tags for the node if present.
+     *
+     * @remarks Returns any JSDoc template tag whose names match the provided
+     * parameter, whether a template tag on a containing function
+     * expression, or a template tag on a variable declaration whose
+     * initializer is the containing function. The tags closest to the
+     * node are returned first, so in the previous example, the template
+     * tag on the containing function expression would be first.
+     */
+    export function getJSDocTypeParameterTags(param: TypeParameterDeclaration): ReadonlyArray<JSDocTemplateTag> {
+        const name = param.name.escapedText;
+        return getJSDocTags(param.parent).filter((tag): tag is JSDocTemplateTag =>
+            isJSDocTemplateTag(tag) && tag.typeParameters.some(tp => tp.name.escapedText === name));
+    }
+
     /**
      * Return true if the node has JSDoc parameter tags.
      *

Diff for: src/services/signatureHelp.ts

@@ -591,6 +591,6 @@ namespace ts.SignatureHelp {
             const param = checker.typeParameterToDeclaration(typeParameter, enclosingDeclaration)!;
             printer.writeNode(EmitHint.Unspecified, param, sourceFile, writer);
         });
-        return { name: typeParameter.symbol.name, documentation: emptyArray, displayParts, isOptional: false };
+        return { name: typeParameter.symbol.name, documentation: typeParameter.symbol.getDocumentationComment(checker), displayParts, isOptional: false };
     }
 }

Diff for: tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -3208,17 +3208,27 @@ declare namespace ts {
     /**
      * Gets the JSDoc parameter tags for the node if present.
      *
-     * @remarks Returns any JSDoc param tag that matches the provided
+     * @remarks Returns any JSDoc param tag whose name matches the provided
      * parameter, whether a param tag on a containing function
      * expression, or a param tag on a variable declaration whose
      * initializer is the containing function. The tags closest to the
      * node are returned first, so in the previous example, the param
      * tag on the containing function expression would be first.
      *
-     * Does not return tags for binding patterns, because JSDoc matches
-     * parameters by name and binding patterns do not have a name.
+     * For binding patterns, parameter tags are matched by position.
      */
     function getJSDocParameterTags(param: ParameterDeclaration): ReadonlyArray<JSDocParameterTag>;
+    /**
+     * Gets the JSDoc type parameter tags for the node if present.
+     *
+     * @remarks Returns any JSDoc template tag whose names match the provided
+     * parameter, whether a template tag on a containing function
+     * expression, or a template tag on a variable declaration whose
+     * initializer is the containing function. The tags closest to the
+     * node are returned first, so in the previous example, the template
+     * tag on the containing function expression would be first.
+     */
+    function getJSDocTypeParameterTags(param: TypeParameterDeclaration): ReadonlyArray<JSDocTemplateTag>;
     /**
      * Return true if the node has JSDoc parameter tags.
      *

Diff for: tests/baselines/reference/api/typescript.d.ts

@@ -3208,17 +3208,27 @@ declare namespace ts {
     /**
      * Gets the JSDoc parameter tags for the node if present.
      *
-     * @remarks Returns any JSDoc param tag that matches the provided
+     * @remarks Returns any JSDoc param tag whose name matches the provided
      * parameter, whether a param tag on a containing function
      * expression, or a param tag on a variable declaration whose
      * initializer is the containing function. The tags closest to the
      * node are returned first, so in the previous example, the param
      * tag on the containing function expression would be first.
      *
-     * Does not return tags for binding patterns, because JSDoc matches
-     * parameters by name and binding patterns do not have a name.
+     * For binding patterns, parameter tags are matched by position.
      */
     function getJSDocParameterTags(param: ParameterDeclaration): ReadonlyArray<JSDocParameterTag>;
+    /**
+     * Gets the JSDoc type parameter tags for the node if present.
+     *
+     * @remarks Returns any JSDoc template tag whose names match the provided
+     * parameter, whether a template tag on a containing function
+     * expression, or a template tag on a variable declaration whose
+     * initializer is the containing function. The tags closest to the
+     * node are returned first, so in the previous example, the template
+     * tag on the containing function expression would be first.
+     */
+    function getJSDocTypeParameterTags(param: TypeParameterDeclaration): ReadonlyArray<JSDocTemplateTag>;
     /**
      * Return true if the node has JSDoc parameter tags.
      *

Diff for: tests/cases/fourslash/signatureHelpTypeArguments2.ts

@@ -0,0 +1,37 @@
+/// <reference path="fourslash.ts"/>
+
+/////** some documentation
+//// * @template T some documentation 2
+//// * @template W
+//// * @template U,V others
+//// * @param a ok
+//// * @param b not ok
+//// */
+////function f<T, U, V, W>(a: number, b: string, c: boolean): void { }
+////f</*f0*/;
+////f<number, /*f1*/;
+////f<number, string, /*f2*/;
+////f<number, string, boolean, /*f3*/;
+
+function build(marker: string, parameterName: string, parameterDocComment: string) {
+    return {
+        marker,
+        text: "f<T, U, V, W>(a: number, b: string, c: boolean): void",
+        parameterName,
+        parameterSpan: parameterName,
+        docComment: "some documentation",
+        parameterDocComment,
+        tags: [{ name: "template", text: "T some documentation 2" },
+               { name: "template", text: "W" },
+               { name: "template", text: "U, V others" },
+               { name: "param", text: "a ok" },
+               { name: "param", text: "b not ok" }]
+    }
+}
+
+verify.signatureHelp(
+    build("f0", "T", "some documentation 2"),
+    build("f1", "U", "others"),
+    build("f2", "V", "others"),
+    build("f3", "W", ""),
+);