feat(types): add (and fix) evaluateHandle types (#6130)

This change started as a small change to pull types from DefinitelyTyped over to
Puppeteer for the `evaluateHandle` function but instead ended up also fixing
what looks to be a long standing issue with our existing documentation.

`evaluateHandle` can in fact return an `ElementHandle` rather than a `JSHandle`.
Note that `ElementHandle` extends `JSHandle` so whilst the docs are technically
correct (all ElementHandles are JSHandles) it's confusing because JSHandles
don't have methods like `click` on them, but ElementHandles do.

if you return something that is an HTML element:

```
const button = page.evaluateHandle(() => document.querySelector('button'));
// this is an ElementHandle, not a JSHandle
```

Therefore I've updated the original docs and added a large explanation to the
TSDoc for `page.evaluateHandle`.

In TypeScript land we'll assume the function will return a `JSHandle` but you
can tell TS otherwise via the generic argument, which can only be `JSHandle`
(the default) or `ElementHandle`:

```
const button = page.evaluateHandle<ElementHandle>(() => document.querySelector('button'));
```

docs/api.md

@@ -1456,7 +1456,7 @@ Shortcut for [page.mainFrame().evaluate(pageFunction, ...args)](#frameevaluatepa
 #### page.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated in the page context
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 The only difference between `page.evaluate` and `page.evaluateHandle` is that `page.evaluateHandle` returns in-page object (JSHandle).
 
@@ -1475,6 +1475,14 @@ console.log(await resultHandle.jsonValue());
 await resultHandle.dispose();
 ```
 
+This function will return a [JSHandle] by default, however if your `pageFunction` returns an HTML element you will get back an `ElementHandle`:
+
+```js
+const button = await page.evaluateHandle(() => document.querySelector('button'))
+// button is an ElementHandle, so you can call methods such as click:
+await button.click();
+```
+
 Shortcut for [page.mainFrame().executionContext().evaluateHandle(pageFunction, ...args)](#executioncontextevaluatehandlepagefunction-args).
 
 #### page.evaluateOnNewDocument(pageFunction[, ...args])
@@ -2298,12 +2306,14 @@ Shortcut for [(await worker.executionContext()).evaluate(pageFunction, ...args)]
 #### webWorker.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated in the page context
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 The only difference between `worker.evaluate` and `worker.evaluateHandle` is that `worker.evaluateHandle` returns in-page object (JSHandle).
 
 If the function passed to the `worker.evaluateHandle` returns a [Promise], then `worker.evaluateHandle` would wait for the promise to resolve and return its value.
 
+If the function returns an element, the returned handle is an [ElementHandle].
+
 Shortcut for [(await worker.executionContext()).evaluateHandle(pageFunction, ...args)](#executioncontextevaluatehandlepagefunction-args).
 
 #### webWorker.executionContext()
@@ -2855,12 +2865,14 @@ await bodyHandle.dispose();
 #### frame.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated in the page context
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 The only difference between `frame.evaluate` and `frame.evaluateHandle` is that `frame.evaluateHandle` returns in-page object (JSHandle).
 
 If the function, passed to the `frame.evaluateHandle`, returns a [Promise], then `frame.evaluateHandle` would wait for the promise to resolve and return its value.
 
+If the function returns an element, the returned handle is an [ElementHandle].
+
 ```js
 const aWindowHandle = await frame.evaluateHandle(() => Promise.resolve(window));
 aWindowHandle; // Handle for the window object.
@@ -3184,10 +3196,12 @@ console.log(result); // prints '3'.
 #### executionContext.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated in the `executionContext`
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 The only difference between `executionContext.evaluate` and `executionContext.evaluateHandle` is that `executionContext.evaluateHandle` returns in-page object (JSHandle).
 
+If the function returns an element, the returned handle is an [ElementHandle].
+
 If the function passed to the `executionContext.evaluateHandle` returns a [Promise], then `executionContext.evaluateHandle` would wait for the promise to resolve and return its value.
 
 ```js
@@ -3277,12 +3291,14 @@ expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10');
 #### jsHandle.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 This method passes this handle as the first argument to `pageFunction`.
 
 The only difference between `jsHandle.evaluate` and `jsHandle.evaluateHandle` is that `executionContext.evaluateHandle` returns in-page object (JSHandle).
 
+If the function returns an element, the returned handle is an [ElementHandle].
+
 If the function passed to the `jsHandle.evaluateHandle` returns a [Promise], then `jsHandle.evaluateHandle` would wait for the promise to resolve and return its value.
 
 See [Page.evaluateHandle](#pageevaluatehandlepagefunction-args) for more details.
@@ -3466,12 +3482,14 @@ expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10');
 #### elementHandle.evaluateHandle(pageFunction[, ...args])
 - `pageFunction` <[function]|[string]> Function to be evaluated
 - `...args` <...[Serializable]|[JSHandle]> Arguments to pass to `pageFunction`
-- returns: <[Promise]<[JSHandle]>> Promise which resolves to the return value of `pageFunction` as in-page object (JSHandle)
+- returns: <[Promise]<[JSHandle]|[ElementHandle]>> Promise which resolves to the return value of `pageFunction` as an in-page object.
 
 This method passes this handle as the first argument to `pageFunction`.
 
 The only difference between `evaluateHandle.evaluate` and `evaluateHandle.evaluateHandle` is that `executionContext.evaluateHandle` returns in-page object (JSHandle).
 
+If the function returns an element, the returned handle is an [ElementHandle].
+
 If the function passed to the `evaluateHandle.evaluateHandle` returns a [Promise], then `evaluateHandle.evaluateHandle` would wait for the promise to resolve and return its value.
 
 See [Page.evaluateHandle](#pageevaluatehandlepagefunction-args) for more details.

new-docs/puppeteer.evaluatehandlefn.md

@@ -0,0 +1,12 @@
+<!-- Do not edit this file. It is automatically generated by API Documenter. -->
+
+[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md)
+
+## EvaluateHandleFn type
+
+
+<b>Signature:</b>
+
+```typescript
+export declare type EvaluateHandleFn = string | ((...args: unknown[]) => unknown);
+```

new-docs/puppeteer.executioncontext.evaluatehandle.md

@@ -7,19 +7,19 @@
 <b>Signature:</b>
 
 ```typescript
-evaluateHandle(pageFunction: Function | string, ...args: unknown[]): Promise<JSHandle>;
+evaluateHandle<HandleType extends JSHandle | ElementHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandleType>;
 ```
 
 ## Parameters
 
 |  Parameter | Type | Description |
 |  --- | --- | --- |
-|  pageFunction | Function \| string | a function to be evaluated in the <code>executionContext</code> |
+|  pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) | a function to be evaluated in the <code>executionContext</code> |
-|  args | unknown\[\] | argument to pass to the page function |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | argument to pass to the page function |
 
 <b>Returns:</b>
 
-Promise&lt;[JSHandle](./puppeteer.jshandle.md)<!-- -->&gt;
+Promise&lt;HandleType&gt;
 
 A promise that resolves to the return value of the given function as an in-page object (a [JSHandle](./puppeteer.jshandle.md)<!-- -->).
 

new-docs/puppeteer.frame.evaluatehandle.md

@@ -7,17 +7,17 @@
 <b>Signature:</b>
 
 ```typescript
-evaluateHandle(pageFunction: Function | string, ...args: unknown[]): Promise<JSHandle>;
+evaluateHandle<HandlerType extends JSHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandlerType>;
 ```
 
 ## Parameters
 
 |  Parameter | Type | Description |
 |  --- | --- | --- |
-|  pageFunction | Function \| string |  |
+|  pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 
-Promise&lt;[JSHandle](./puppeteer.jshandle.md)<!-- -->&gt;
+Promise&lt;HandlerType&gt;
 

new-docs/puppeteer.frame.waitfor.md

@@ -7,7 +7,7 @@
 <b>Signature:</b>
 
 ```typescript
-waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {}, ...args: unknown[]): Promise<JSHandle | null>;
+waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {}, ...args: SerializableOrJSHandle[]): Promise<JSHandle | null>;
 ```
 
 ## Parameters
@@ -16,7 +16,7 @@ waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {}, .
 |  --- | --- | --- |
 |  selectorOrFunctionOrTimeout | string \| number \| Function |  |
 |  options | {} |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 

new-docs/puppeteer.frame.waitforfunction.md

@@ -10,7 +10,7 @@
 waitForFunction(pageFunction: Function | string, options?: {
         polling?: string | number;
         timeout?: number;
-    }, ...args: unknown[]): Promise<JSHandle>;
+    }, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;
 ```
 
 ## Parameters
@@ -19,7 +19,7 @@ waitForFunction(pageFunction: Function | string, options?: {
 |  --- | --- | --- |
 |  pageFunction | Function \| string |  |
 |  options | { polling?: string \| number; timeout?: number; } |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 

new-docs/puppeteer.jshandle.evaluatehandle.md

@@ -9,19 +9,19 @@ This method passes this handle as the first argument to `pageFunction`<!-- -->.
 <b>Signature:</b>
 
 ```typescript
-evaluateHandle(pageFunction: Function | string, ...args: unknown[]): Promise<JSHandle>;
+evaluateHandle<HandleType extends JSHandle | ElementHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandleType>;
 ```
 
 ## Parameters
 
 |  Parameter | Type | Description |
 |  --- | --- | --- |
-|  pageFunction | Function \| string |  |
+|  pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 
-Promise&lt;[JSHandle](./puppeteer.jshandle.md)<!-- -->&gt;
+Promise&lt;HandleType&gt;
 
 ## Remarks
 

new-docs/puppeteer.md

@@ -82,6 +82,7 @@
 |  [ConsoleMessageType](./puppeteer.consolemessagetype.md) | The supported types for console messages. |
 |  [EvaluateFn](./puppeteer.evaluatefn.md) |  |
 |  [EvaluateFnReturnType](./puppeteer.evaluatefnreturntype.md) |  |
+|  [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) |  |
 |  [JSONArray](./puppeteer.jsonarray.md) |  |
 |  [KeyInput](./puppeteer.keyinput.md) |  |
 |  [MouseButtonInput](./puppeteer.mousebuttoninput.md) |  |

new-docs/puppeteer.page.evaluatehandle.md

@@ -7,17 +7,62 @@
 <b>Signature:</b>
 
 ```typescript
-evaluateHandle(pageFunction: Function | string, ...args: unknown[]): Promise<JSHandle>;
+evaluateHandle<HandlerType extends JSHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<HandlerType>;
 ```
 
 ## Parameters
 
 |  Parameter | Type | Description |
 |  --- | --- | --- |
-|  pageFunction | Function \| string |  |
+|  pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) | a function that is run within the page |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | arguments to be passed to the pageFunction |
 
 <b>Returns:</b>
 
-Promise&lt;[JSHandle](./puppeteer.jshandle.md)<!-- -->&gt;
+Promise&lt;HandlerType&gt;
+
+## Remarks
+
+The only difference between [page.evaluate](./puppeteer.page.evaluate.md) and `page.evaluateHandle` is that `evaluateHandle` will return the value wrapped in an in-page object.
+
+If the function passed to `page.evaluteHandle` returns a Promise, the function will wait for the promise to resolve and return its value.
+
+You can pass a string instead of a function (although functions are recommended as they are easier to debug and use with TypeScript):
+
+## Example 1
+
+
+```
+const aHandle = await page.evaluateHandle('document')
+
+```
+
+## Example 2
+
+[JSHandle](./puppeteer.jshandle.md) instances can be passed as arguments to the `pageFunction`<!-- -->:
+
+```
+const aHandle = await page.evaluateHandle(() => document.body);
+const resultHandle = await page.evaluateHandle(body => body.innerHTML, aHandle);
+console.log(await resultHandle.jsonValue());
+await resultHandle.dispose();
+
+```
+Most of the time this function returns a [JSHandle](./puppeteer.jshandle.md)<!-- -->, but if `pageFunction` returns a reference to an element, you instead get an [ElementHandle](./puppeteer.elementhandle.md) back:
+
+## Example 3
+
+
+```
+const button = await page.evaluateHandle(() => document.querySelector('button'));
+// can call `click` because `button` is an `ElementHandle`
+await button.click();
+
+```
+The TypeScript definitions assume that `evaluateHandle` returns a `JSHandle`<!-- -->, but if you know it's going to return an `ElementHandle`<!-- -->, pass it as the generic argument:
+
+```
+const button = await page.evaluateHandle<ElementHandle>(...);
+
+```
 

new-docs/puppeteer.page.waitfor.md

@@ -12,7 +12,7 @@ waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {
         hidden?: boolean;
         timeout?: number;
         polling?: string | number;
-    }, ...args: unknown[]): Promise<JSHandle>;
+    }, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;
 ```
 
 ## Parameters
@@ -21,7 +21,7 @@ waitFor(selectorOrFunctionOrTimeout: string | number | Function, options?: {
 |  --- | --- | --- |
 |  selectorOrFunctionOrTimeout | string \| number \| Function |  |
 |  options | { visible?: boolean; hidden?: boolean; timeout?: number; polling?: string \| number; } |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 

new-docs/puppeteer.page.waitforfunction.md

@@ -10,7 +10,7 @@
 waitForFunction(pageFunction: Function | string, options?: {
         timeout?: number;
         polling?: string | number;
-    }, ...args: unknown[]): Promise<JSHandle>;
+    }, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;
 ```
 
 ## Parameters
@@ -19,7 +19,7 @@ waitForFunction(pageFunction: Function | string, options?: {
 |  --- | --- | --- |
 |  pageFunction | Function \| string |  |
 |  options | { timeout?: number; polling?: string \| number; } |  |
-|  args | unknown\[\] |  |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] |  |
 
 <b>Returns:</b>
 

new-docs/puppeteer.webworker.evaluatehandle.md

@@ -9,15 +9,15 @@ The only difference between `worker.evaluate` and `worker.evaluateHandle` is tha
 <b>Signature:</b>
 
 ```typescript
-evaluateHandle(pageFunction: Function | string, ...args: any[]): Promise<JSHandle>;
+evaluateHandle<HandlerType extends JSHandle = JSHandle>(pageFunction: EvaluateHandleFn, ...args: SerializableOrJSHandle[]): Promise<JSHandle>;
 ```
 
 ## Parameters
 
 |  Parameter | Type | Description |
 |  --- | --- | --- |
-|  pageFunction | Function \| string | Function to be evaluated in the page context. |
+|  pageFunction | [EvaluateHandleFn](./puppeteer.evaluatehandlefn.md) | Function to be evaluated in the page context. |
-|  args | any\[\] | Arguments to pass to <code>pageFunction</code>. |
+|  args | [SerializableOrJSHandle](./puppeteer.serializableorjshandle.md)<!-- -->\[\] | Arguments to pass to <code>pageFunction</code>. |
 
 <b>Returns:</b>
 

src/common/DOMWorld.ts

@@ -24,7 +24,11 @@ import { TimeoutSettings } from './TimeoutSettings';
 import { MouseButtonInput } from './Input';
 import { FrameManager, Frame } from './FrameManager';
 import { getQueryHandlerAndSelector, QueryHandler } from './QueryHandler';
-import { EvaluateFn, SerializableOrJSHandle } from './EvalTypes';
+import {
+  EvaluateFn,
+  SerializableOrJSHandle,
+  EvaluateHandleFn,
+} from './EvalTypes';
 import { isNode } from '../environment';
 
 // This predicateQueryHandler is declared here so that TypeScript knows about it
@@ -103,15 +107,10 @@ export class DOMWorld {
     return this._contextPromise;
   }
 
-  /**
+  async evaluateHandle<HandlerType extends JSHandle = JSHandle>(
-   * @param {Function|string} pageFunction
+    pageFunction: EvaluateHandleFn,
-   * @param {!Array<*>} args
+    ...args: SerializableOrJSHandle[]
-   * @returns {!Promise<!JSHandle>}
+  ): Promise<HandlerType> {
-   */
-  async evaluateHandle(
-    pageFunction: Function | string,
-    ...args: unknown[]
-  ): Promise<JSHandle> {
     const context = await this.executionContext();
     return context.evaluateHandle(pageFunction, ...args);
   }
@@ -470,7 +469,7 @@ export class DOMWorld {
   waitForFunction(
     pageFunction: Function | string,
     options: { polling?: string | number; timeout?: number } = {},
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle> {
     const {
       polling = 'raf',
@@ -581,7 +580,7 @@ class WaitTask {
   _polling: string | number;
   _timeout: number;
   _predicateBody: string;
-  _args: unknown[];
+  _args: SerializableOrJSHandle[];
   _runCount = 0;
   promise: Promise<JSHandle>;
   _resolve: (x: JSHandle) => void;
@@ -596,7 +595,7 @@ class WaitTask {
     title: string,
     polling: string | number,
     timeout: number,
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ) {
     if (helper.isString(polling))
       assert(

src/common/EvalTypes.ts

@@ -29,6 +29,11 @@ export type EvaluateFnReturnType<T extends EvaluateFn> = T extends (
   ? R
   : unknown;
 
+/**
+ * @public
+ */
+export type EvaluateHandleFn = string | ((...args: unknown[]) => unknown);
+
 /**
  * @public
  */

src/common/ExecutionContext.ts

@@ -21,6 +21,7 @@ import { CDPSession } from './Connection';
 import { DOMWorld } from './DOMWorld';
 import { Frame } from './FrameManager';
 import Protocol from '../protocol';
+import { EvaluateHandleFn, SerializableOrJSHandle } from './EvalTypes';
 
 export const EVALUATION_SCRIPT_URL = '__puppeteer_evaluation_script__';
 const SOURCE_URL_REGEX = /^[\040\t]*\/\/[@#] sourceURL=\s*(\S*?)\s*$/m;
@@ -175,15 +176,15 @@ export class ExecutionContext {
    * @returns A promise that resolves to the return value of the given function
    * as an in-page object (a {@link JSHandle}).
    */
-  async evaluateHandle(
+  async evaluateHandle<HandleType extends JSHandle | ElementHandle = JSHandle>(
-    pageFunction: Function | string,
+    pageFunction: EvaluateHandleFn,
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
-  ): Promise<JSHandle> {
+  ): Promise<HandleType> {
-    return this._evaluateInternal<JSHandle>(false, pageFunction, ...args);
+    return this._evaluateInternal<HandleType>(false, pageFunction, ...args);
   }
 
   private async _evaluateInternal<ReturnType>(
-    returnByValue,
+    returnByValue: boolean,
     pageFunction: Function | string,
     ...args: unknown[]
   ): Promise<ReturnType> {

src/common/FrameManager.ts

@@ -29,7 +29,11 @@ import { MouseButtonInput } from './Input';
 import { Page } from './Page';
 import { HTTPResponse } from './HTTPResponse';
 import Protocol from '../protocol';
-import { EvaluateFn, SerializableOrJSHandle } from './EvalTypes';
+import {
+  EvaluateFn,
+  SerializableOrJSHandle,
+  EvaluateHandleFn,
+} from './EvalTypes';
 
 const UTILITY_WORLD_NAME = '__puppeteer_utility_world__';
 
@@ -431,11 +435,11 @@ export class Frame {
     return this._mainWorld.executionContext();
   }
 
-  async evaluateHandle(
+  async evaluateHandle<HandlerType extends JSHandle = JSHandle>(
-    pageFunction: Function | string,
+    pageFunction: EvaluateHandleFn,
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
-  ): Promise<JSHandle> {
+  ): Promise<HandlerType> {
-    return this._mainWorld.evaluateHandle(pageFunction, ...args);
+    return this._mainWorld.evaluateHandle<HandlerType>(pageFunction, ...args);
   }
 
   async evaluate<ReturnType extends any>(
@@ -562,7 +566,7 @@ export class Frame {
   waitFor(
     selectorOrFunctionOrTimeout: string | number | Function,
     options: {} = {},
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle | null> {
     const xPathPattern = '//';
 
@@ -619,7 +623,7 @@ export class Frame {
   waitForFunction(
     pageFunction: Function | string,
     options: { polling?: string | number; timeout?: number } = {},
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle> {
     return this._mainWorld.waitForFunction(pageFunction, options, ...args);
   }

src/common/JSHandle.ts

@@ -27,6 +27,7 @@ import {
   EvaluateFn,
   SerializableOrJSHandle,
   EvaluateFnReturnType,
+  EvaluateHandleFn,
 } from './EvalTypes';
 
 export interface BoxModel {
@@ -174,10 +175,10 @@ export class JSHandle {
    *
    * See {@link Page.evaluateHandle} for more details.
    */
-  async evaluateHandle(
+  async evaluateHandle<HandleType extends JSHandle | ElementHandle = JSHandle>(
-    pageFunction: Function | string,
+    pageFunction: EvaluateHandleFn,
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
-  ): Promise<JSHandle> {
+  ): Promise<HandleType> {
     return await this.executionContext().evaluateHandle(
       pageFunction,
       this,
@@ -891,19 +892,22 @@ export class ElementHandle extends JSHandle {
    * @param expression - Expression to {@link https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate | evaluate}
    */
   async $x(expression: string): Promise<ElementHandle[]> {
-    const arrayHandle = await this.evaluateHandle((element, expression) => {
+    const arrayHandle = await this.evaluateHandle(
-      const document = element.ownerDocument || element;
+      (element: Document, expression: string) => {
-      const iterator = document.evaluate(
+        const document = element.ownerDocument || element;
-        expression,
+        const iterator = document.evaluate(
-        element,
+          expression,
-        null,
+          element,
-        XPathResult.ORDERED_NODE_ITERATOR_TYPE
+          null,
-      );
+          XPathResult.ORDERED_NODE_ITERATOR_TYPE
-      const array = [];
+        );
-      let item;
+        const array = [];
-      while ((item = iterator.iterateNext())) array.push(item);
+        let item;
-      return array;
+        while ((item = iterator.iterateNext())) array.push(item);
-    }, expression);
+        return array;
+      },
+      expression
+    );
     const properties = await arrayHandle.getProperties();
     await arrayHandle.dispose();
     const result = [];

src/common/Page.ts

@@ -42,7 +42,11 @@ import { FileChooser } from './FileChooser';
 import { ConsoleMessage, ConsoleMessageType } from './ConsoleMessage';
 import { PuppeteerLifeCycleEvent } from './LifecycleWatcher';
 import Protocol from '../protocol';
-import { EvaluateFn, SerializableOrJSHandle } from './EvalTypes';
+import {
+  EvaluateFn,
+  SerializableOrJSHandle,
+  EvaluateHandleFn,
+} from './EvalTypes';
 
 const writeFileAsync = promisify(fs.writeFile);
 
@@ -639,12 +643,61 @@ export class Page extends EventEmitter {
     return this.mainFrame().$(selector);
   }
 
-  async evaluateHandle(
+  /**
-    pageFunction: Function | string,
+   * @remarks
-    ...args: unknown[]
+   *
-  ): Promise<JSHandle> {
+   * The only difference between {@link Page.evaluate | page.evaluate} and
+   * `page.evaluateHandle` is that `evaluateHandle` will return the value
+   * wrapped in an in-page object.
+   *
+   * If the function passed to `page.evaluteHandle` returns a Promise, the
+   * function will wait for the promise to resolve and return its value.
+   *
+   * You can pass a string instead of a function (although functions are
+   * recommended as they are easier to debug and use with TypeScript):
+   *
+   * @example
+   * ```
+   * const aHandle = await page.evaluateHandle('document')
+   * ```
+   *
+   * @example
+   * {@link JSHandle} instances can be passed as arguments to the `pageFunction`:
+   * ```
+   * const aHandle = await page.evaluateHandle(() => document.body);
+   * const resultHandle = await page.evaluateHandle(body => body.innerHTML, aHandle);
+   * console.log(await resultHandle.jsonValue());
+   * await resultHandle.dispose();
+   * ```
+   *
+   * Most of the time this function returns a {@link JSHandle},
+   * but if `pageFunction` returns a reference to an element,
+   * you instead get an {@link ElementHandle} back:
+   *
+   * @example
+   * ```
+   * const button = await page.evaluateHandle(() => document.querySelector('button'));
+   * // can call `click` because `button` is an `ElementHandle`
+   * await button.click();
+   * ```
+   *
+   * The TypeScript definitions assume that `evaluateHandle` returns
+   *  a `JSHandle`, but if you know it's going to return an
+   * `ElementHandle`, pass it as the generic argument:
+   *
+   * ```
+   * const button = await page.evaluateHandle<ElementHandle>(...);
+   * ```
+   *
+   * @param pageFunction - a function that is run within the page
+   * @param args - arguments to be passed to the pageFunction
+   */
+  async evaluateHandle<HandlerType extends JSHandle = JSHandle>(
+    pageFunction: EvaluateHandleFn,
+    ...args: SerializableOrJSHandle[]
+  ): Promise<HandlerType> {
     const context = await this.mainFrame().executionContext();
-    return context.evaluateHandle(pageFunction, ...args);
+    return context.evaluateHandle<HandlerType>(pageFunction, ...args);
   }
 
   async queryObjects(prototypeHandle: JSHandle): Promise<JSHandle> {
@@ -1471,7 +1524,7 @@ export class Page extends EventEmitter {
       timeout?: number;
       polling?: string | number;
     } = {},
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle> {
     return this.mainFrame().waitFor(
       selectorOrFunctionOrTimeout,
@@ -1508,7 +1561,7 @@ export class Page extends EventEmitter {
       timeout?: number;
       polling?: string | number;
     } = {},
-    ...args: unknown[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle> {
     return this.mainFrame().waitForFunction(pageFunction, options, ...args);
   }

src/common/WebWorker.ts

@@ -19,6 +19,7 @@ import { ExecutionContext } from './ExecutionContext';
 import { JSHandle } from './JSHandle';
 import { CDPSession } from './Connection';
 import Protocol from '../protocol';
+import { EvaluateHandleFn, SerializableOrJSHandle } from './EvalTypes';
 
 type ConsoleAPICalledCallback = (
   eventType: string,
@@ -152,11 +153,11 @@ export class WebWorker extends EventEmitter {
    * @param args - Arguments to pass to `pageFunction`.
    * @returns Promise which resolves to the return value of `pageFunction`.
    */
-  async evaluateHandle(
+  async evaluateHandle<HandlerType extends JSHandle = JSHandle>(
-    pageFunction: Function | string,
+    pageFunction: EvaluateHandleFn,
-    ...args: any[]
+    ...args: SerializableOrJSHandle[]
   ): Promise<JSHandle> {
-    return (await this._executionContextPromise).evaluateHandle(
+    return (await this._executionContextPromise).evaluateHandle<HandlerType>(
       pageFunction,
       ...args
     );

test/elementhandle.spec.ts

@@ -182,17 +182,11 @@ describe('ElementHandle specs', function () {
       const { page, server } = getTestState();
 
       await page.goto(server.PREFIX + '/shadow.html');
-      const buttonHandle = await page.evaluateHandle(
+      const buttonHandle = await page.evaluateHandle<ElementHandle>(
         // @ts-expect-error button is expected to be in the page's scope.
         () => button
       );
-      // TODO (@jackfranklin): TS types are off here. evaluateHandle returns a
+      await buttonHandle.click();
-      // JSHandle but that doesn't have a click() method. In this case it seems
-      // to return an ElementHandle. I'm not sure if the tests are wrong here
-      // and should use evaluate<ElementHandle> or if the type of evaluateHandle
-      // should change to enable the user to tell us they are expecting an
-      // ElementHandle rather than the default JSHandle.
-      await (buttonHandle as ElementHandle).click();
       expect(
         await page.evaluate(
           // @ts-expect-error clicked is expected to be in the page's scope.

test/jshandle.spec.ts

@@ -53,6 +53,7 @@ describe('JSHandle', function () {
       const aHandle = await page.evaluateHandle(() => document.body);
       let error = null;
       await page
+        // @ts-expect-error we are deliberately passing a bad type here (nested object)
         .evaluateHandle((opts) => opts.elem.querySelector('p'), {
           elem: aHandle,
         })