metamask-extension/app/scripts/lib/rpc-method-middleware/handlers/log-web3-shim-usage.js

import { MESSAGE_TYPE } from '../../enums'

/**
 * This RPC method is called by the inpage provider whenever it detects the
 * accessing of a non-existent property on our window.web3 shim.
 * We collect this data to understand which sites are breaking due to the
 * removal of our window.web3.
 */

const logWeb3ShimUsage = {
  methodNames: [MESSAGE_TYPE.LOG_WEB3_SHIM_USAGE],
  implementation: logWeb3ShimUsageHandler,
}
export default logWeb3ShimUsage

const recordedWeb3ShimUsage = {}

/**
 * @typedef {Object} LogWeb3ShimUsageOptions
 * @property {Function} sendMetrics - A function that registers a metrics event.
 */

/**
 * @param {import('json-rpc-engine').JsonRpcRequest<unknown>} req - The JSON-RPC request object.
 * @param {import('json-rpc-engine').JsonRpcResponse<true>} res - The JSON-RPC response object.
 * @param {Function} _next - The json-rpc-engine 'next' callback.
 * @param {Function} end - The json-rpc-engine 'end' callback.
 * @param {LogWeb3ShimUsageOptions} options
 */
function logWeb3ShimUsageHandler(req, res, _next, end, { sendMetrics }) {
  const { origin } = req
  if (!recordedWeb3ShimUsage[origin]) {
    recordedWeb3ShimUsage[origin] = true

    sendMetrics({
      event: `Website Accessed window.web3 Shim`,
      category: 'inpage_provider',
      eventContext: {
        referrer: {
          url: origin,
        },
      },
      excludeMetaMetricsId: true,
    })
  }

  res.result = true
  return end()
}