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Wolfgang Beyer e046c23563 chore: in-page tool output: stash DOM elements and preprocess for serialization (#1877)
Improvements for handling in-page tool responses. In order to
successfully pass an in-page tool response from the page context to the
MCP server, the response needs to be serializable. The code walks the
response object an performs the following changes:

- DOM elements are stashed onto the window object and replaced with an
ID. On the MCP server side this ID is used to map back to the
corresponding UID in the page snapshot generated from the accessibility
tree.
- Circular references are replaced with a string.
- Class instances (which can be complex or non-serializable) are
replaced with a string.
- Functions are replaced with a string.

If the in-page tool response contains DOM elements which are not part of
the page snapshot, a new snapshot is created add the missing elements
are added explicitly.
2026-04-22 14:51:09 +00:00

307 行
7.5 KiB
TypeScript

/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import assert from 'node:assert';
import {describe, it} from 'node:test';
import type {ElementHandle} from 'puppeteer-core';
import {SnapshotFormatter} from '../../src/formatters/SnapshotFormatter.js';
import type {TextSnapshot} from '../../src/TextSnapshot.js';
import type {TextSnapshotNode} from '../../src/types.js';
describe('snapshotFormatter', () => {
it('formats a snapshot with value properties', () => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'textbox',
name: 'textbox',
value: 'value',
live: 'polite',
relevant: 'additions',
errormessage: 'error-id',
details: 'details-id',
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({root: node} as TextSnapshot);
const formatted = formatter.toString();
assert.strictEqual(
formatted,
`uid=1_1 textbox "textbox" details="details-id" errormessage="error-id" live="polite" relevant="additions" value="value"
uid=1_2 statictext "text"
`,
);
});
it('formats a snapshot with boolean properties', () => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'button',
name: 'button',
disabled: true,
busy: true,
atomic: true,
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({root: node} as TextSnapshot);
const formatted = formatter.toString();
assert.strictEqual(
formatted,
`uid=1_1 button "button" atomic busy disableable disabled
uid=1_2 statictext "text"
`,
);
});
it('formats a snapshot with checked properties', () => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'checkbox',
name: 'checkbox',
checked: true,
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({root: node} as TextSnapshot);
const formatted = formatter.toString();
assert.strictEqual(
formatted,
`uid=1_1 checkbox "checkbox" checked
uid=1_2 statictext "text"
`,
);
});
it('formats a snapshot with multiple different type attributes', () => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'root',
name: 'root',
children: [
{
id: '1_2',
role: 'button',
name: 'button',
focused: true,
disabled: true,
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
{
id: '1_3',
role: 'textbox',
name: 'textbox',
value: 'value',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({root: node} as TextSnapshot);
const formatted = formatter.toString();
assert.strictEqual(
formatted,
`uid=1_1 root "root"
uid=1_2 button "button" disableable disabled focusable focused
uid=1_3 textbox "textbox" value="value"
`,
);
});
it('formats with DevTools data not included into a snapshot', t => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'checkbox',
name: 'checkbox',
checked: true,
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({
snapshotId: '1',
root: node,
idToNode: new Map(),
hasSelectedElement: true,
verbose: false,
});
const formatted = formatter.toString();
t.assert.snapshot?.(formatted);
});
it('does not include a note if the snapshot is already verbose', t => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'checkbox',
name: 'checkbox',
checked: true,
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({
snapshotId: '1',
root: node,
idToNode: new Map(),
hasSelectedElement: true,
verbose: true,
});
const formatted = formatter.toString();
t.assert.snapshot?.(formatted);
});
it('formats with DevTools data included into a snapshot', t => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'checkbox',
name: 'checkbox',
checked: true,
children: [
{
id: '1_2',
role: 'statictext',
name: 'text',
children: [],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
},
],
elementHandle: async (): Promise<ElementHandle<Element> | null> => {
return null;
},
};
const formatter = new SnapshotFormatter({
snapshotId: '1',
root: node,
idToNode: new Map(),
hasSelectedElement: true,
selectedElementUid: '1_1',
verbose: false,
});
const formatted = formatter.toString();
t.assert.snapshot?.(formatted);
});
it('toJSON returns expected structure', () => {
const node: TextSnapshotNode = {
id: '1_1',
role: 'root',
name: 'root',
busy: true,
live: 'polite',
children: [
{
id: '1_2',
role: 'button',
name: 'button',
disabled: true,
children: [],
elementHandle: async () => null,
},
],
elementHandle: async () => null,
};
const formatter = new SnapshotFormatter({root: node} as TextSnapshot);
const json = formatter.toJSON();
assert.deepStrictEqual(json, {
id: '1_1',
role: 'root',
name: 'root',
busy: true,
live: 'polite',
children: [
{
id: '1_2',
role: 'button',
name: 'button',
disableable: true,
disabled: true,
},
],
});
});
});