fix(fill): throw when the element isn't fillable (#160)

An element is fillable if its:
- In dom
- Not display:none or visibility:hidden
- textarea or input or contenteditable

if textarea or input it must also be
- not readOnly
- not disabled

#133

src/dom.ts

@@ -335,8 +335,6 @@ export class ElementHandle<T extends Node = Node> extends js.JSHandle<T> {
     const error = await this.evaluate(input.fillFunction);
     if (error)
       throw new Error(error);
-    await this.focus();
-    // TODO: we should check that focus() succeeded.
     await this._world.delegate.keyboard.sendCharacters(value);
   }
 

src/input.ts

@@ -320,26 +320,45 @@ export const fillFunction = (node: Node) => {
   if (node.nodeType !== Node.ELEMENT_NODE)
     return 'Node is not of type HTMLElement';
   const element = node as HTMLElement;
+  if (!element.isConnected)
+    return 'Element is not attached to the DOM';
+  if (!element.ownerDocument || !element.ownerDocument.defaultView)
+    return 'Element does not belong to a window';
+
+  const style = element.ownerDocument.defaultView.getComputedStyle(element);
+  if (!style || style.visibility === 'hidden')
+    return 'Element is hidden';
+  if (!element.offsetParent && element.tagName !== 'BODY')
+    return 'Element is not visible';
   if (element.nodeName.toLowerCase() === 'input') {
     const input = element as HTMLInputElement;
     const type = input.getAttribute('type') || '';
     const kTextInputTypes = new Set(['', 'password', 'search', 'tel', 'text', 'url']);
     if (!kTextInputTypes.has(type.toLowerCase()))
       return 'Cannot fill input of type "' + type + '".';
+    if (input.disabled)
+      return 'Cannot fill a disabled input.';
+    if (input.readOnly)
+      return 'Cannot fill a readonly input.';
     input.selectionStart = 0;
     input.selectionEnd = input.value.length;
+    input.focus();
   } else if (element.nodeName.toLowerCase() === 'textarea') {
     const textarea = element as HTMLTextAreaElement;
+    if (textarea.disabled)
+      return 'Cannot fill a disabled textarea.';
+    if (textarea.readOnly)
+      return 'Cannot fill a readonly textarea.';
     textarea.selectionStart = 0;
     textarea.selectionEnd = textarea.value.length;
+    textarea.focus();
   } else if (element.isContentEditable) {
-    if (!element.ownerDocument || !element.ownerDocument.defaultView)
-      return 'Element does not belong to a window';
     const range = element.ownerDocument.createRange();
     range.selectNodeContents(element);
     const selection = element.ownerDocument.defaultView.getSelection();
     selection.removeAllRanges();
     selection.addRange(range);
+    element.focus();
   } else {
     return 'Element is not an <input>, <textarea> or [contenteditable] element.';
   }

test/page.spec.js

@@ -1133,11 +1133,42 @@ module.exports.addTests = function({testRunner, expect, headless, playwright, FF
       await page.$eval('input', i => i.style.display = 'none');
       await page.fill({selector: 'input', visible: true}, 'some value').catch(e => error = e);
       expect(error.message).toBe('No node found for selector: [visible] input');
+    });
+    it('should throw on disabled and readonly elements', async({page, server}) => {
+      await page.goto(server.PREFIX + '/input/textarea.html');
+      await page.$eval('input', i => i.disabled = true);
+      const disabledError = await page.fill('input', 'some value').catch(e => e);
+      expect(disabledError.message).toBe('Cannot fill a disabled input.');
 
+      await page.goto(server.PREFIX + '/input/textarea.html');
+      await page.$eval('textarea', i => i.readOnly = true);
+      const readonlyError = await page.fill('textarea', 'some value').catch(e => e);
+      expect(readonlyError.message).toBe('Cannot fill a readonly textarea.');
+    });
+    it('should throw on hidden and invisible elements', async({page, server}) => {
       await page.goto(server.PREFIX + '/input/textarea.html');
       await page.$eval('input', i => i.style.display = 'none');
-      await page.fill({selector: 'input', visible: false}, 'some value');
-      expect(await page.evaluate(() => result)).toBe('');
+      const invisibleError = await page.fill('input', 'some value').catch(e => e);
+      expect(invisibleError.message).toBe('Element is not visible');
+
+      await page.goto(server.PREFIX + '/input/textarea.html');
+      await page.$eval('input', i => i.style.visibility = 'hidden');
+      const hiddenError = await page.fill('input', 'some value').catch(e => e);
+      expect(hiddenError.message).toBe('Element is hidden');
+    });
+    it('should be able to fill the body', async({page}) => {
+      await page.setContent(`<body contentEditable="true"></body>`);
+      await page.fill('body', 'some value');
+      expect(await page.evaluate(() => document.body.textContent)).toBe('some value');
+    });
+    it('should be able to fill when focus is in the wrong frame', async({page}) => {
+      await page.setContent(`
+        <div contentEditable="true"></div>
+        <iframe></iframe>
+      `);
+      await page.focus('iframe');
+      await page.fill('div', 'some value');
+      expect(await page.$eval('div', d => d.textContent)).toBe('some value');
     });
   });