Show warning message.

packages/driver/cypress/integration/util/breaking_change_warnings_spec.js

@@ -0,0 +1,41 @@
+describe('blob-util 2.x', () => {
+  it('arrayBufferToBlob', () => {
+    cy.on('fail', (err) => {
+      expect(err.message).to.include('Cypress 5+ uses `blob-util` 2.x')
+    })
+
+    Cypress.Blob.arrayBufferToBlob('1234').then((blob) => {
+      // it should fail.
+    })
+  })
+
+  it('base64StringToBlob', () => {
+    cy.on('fail', (err) => {
+      expect(err.message).to.include('Cypress 5+ uses `blob-util` 2.x')
+    })
+
+    Cypress.Blob.base64StringToBlob('1234').then((blob) => {
+      // it should fail.
+    })
+  })
+
+  it('binaryStringToBlob', () => {
+    cy.on('fail', (err) => {
+      expect(err.message).to.include('Cypress 5+ uses `blob-util` 2.x')
+    })
+
+    Cypress.Blob.binaryStringToBlob('0100101').then((blob) => {
+      // it should fail.
+    })
+  })
+
+  it('dataURLToBlob', () => {
+    cy.on('fail', (err) => {
+      expect(err.message).to.include('Cypress 5+ uses `blob-util` 2.x')
+    })
+
+    Cypress.Blob.dataURLToBlob('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==').then((blob) => {
+      // it should fail.
+    })
+  })
+})

packages/driver/src/cypress.js

@@ -34,6 +34,7 @@ const $scriptUtils = require('./cypress/script_utils')
 const browserInfo = require('./cypress/browser')
 const resolvers = require('./cypress/resolvers')
 const debug = require('debug')('cypress:driver:cypress')
+const { wrapBlobUtil } = require('./util/breaking_change_warning')
 
 const jqueryProxyFn = function (...args) {
   if (!this.cy) {
@@ -613,7 +614,7 @@ $Cypress.prototype.SelectorPlayground = $SelectorPlayground
 $Cypress.prototype.utils = $utils
 $Cypress.prototype._ = _
 $Cypress.prototype.moment = moment
-$Cypress.prototype.Blob = blobUtil
+$Cypress.prototype.Blob = wrapBlobUtil(blobUtil)
 $Cypress.prototype.Promise = Promise
 $Cypress.prototype.minimatch = minimatch
 $Cypress.prototype.sinon = sinon

packages/driver/src/cypress/error_messages.js

@@ -153,6 +153,13 @@ module.exports = {
     },
   },
 
+  breaking_change: {
+    blob_util2: {
+      message: 'Cypress 5+ uses `blob-util` 2.x. This function does not return `Promise` any more.',
+      docsUrl: 'https://docs.cypress.io/guides/references/migration-guide.html',
+    },
+  },
+
   browser: {
     invalid_arg: '{{prefix}} must be passed a string, object, or an array. You passed: `{{obj}}`',
   },

packages/driver/src/util/breaking_change_warning.ts

@@ -0,0 +1,30 @@
+import $errUtil from '../cypress/error_utils'
+
+export function wrapBlobUtil (blobUtil) {
+  const breakingChanges = [
+    'arrayBufferToBlob',
+    'base64StringToBlob',
+    'binaryStringToBlob',
+    'dataURLToBlob',
+  ]
+
+  const obj = {}
+
+  Object.keys(blobUtil).forEach((key) => {
+    if (breakingChanges.includes(key)) {
+      obj[key] = function (...args) {
+        const val = blobUtil[key](...args)
+
+        val.then = function () {
+          $errUtil.throwErrByPath('breaking_change.blob_util2')
+        }
+
+        return val
+      }
+    } else {
+      obj[key] = blobUtil[key]
+    }
+  })
+
+  return obj
+}