Blitz apps crash when run in an iFrame in Chrome when third-party cookies are disabled

[mtford90]

What is the problem?

This is quite an obscure problem - we discovered it after integrating a form from our Blitz app in an iframe within our webflow landing page.

If third-party cookies are disabled then a Blitz app will crash when run in an iFrame in chrome.

This is Chrome's default setting when running in incognito.

As a side effect of third-party cookies being disabled, localStorage is also disabled. Because Blitz relies on localStorage within PublicDataStore:

  updateState(value?: PublicData | EmptyPublicData, opts?: {suppressEvent: boolean}) {
    // We use localStorage as a message bus between tabs.
    // Setting the current time in ms will cause other tabs to receive the `storage` event
    if (!opts?.suppressEvent) {
      // Prevent infinite loop
      localStorage.setItem(this.eventKey, Date.now().toString())
    }
    this.observable.next(value ?? this.getData())
  }

This problem can be fixed by wrapping the localStorage.setItem call in a try/catch block

Paste all your error logs here:

DOMException: Failed to read the 'localStorage' property from 'Window': Access is denied for this document.

Paste all relevant code snippets here:

PASTE_HERE (leave the ``` marks)

What are detailed steps to reproduce this?

1. Try to load a blitz app in an iframe in Chrome when third-party cookies are disabled.
2. Observe the following error: DOMException: Failed to read the 'localStorage' property from 'Window': Access is denied for this document.

Run blitz -v and paste the output here:

➜  app git:(master) blitz -v     
You are using beta software - if you have any problems, please open an issue here:
      https://github.com/blitz-js/blitz/issues/new/choose

macOS Catalina | darwin-x64 | Node: v12.20.0

blitz: 0.30.1 (global)
blitz: 0.33.1 (local)

  Package manager: npm 
  System:
    OS: macOS 10.15.6
    CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
    Memory: 24.00 GB / 64.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 12.20.0 - ~/.nvm/versions/node/v12.20.0/bin/node
    Yarn: 1.22.4 - ~/.nvm/versions/node/v12.20.0/bin/yarn
    npm: 6.14.8 - ~/.nvm/versions/node/v12.20.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  npmPackages:
    @prisma/client: ~2.20.1 => 2.20.1 
    blitz: 0.33.1 => 0.33.1 
    prisma: ~2.20.1 => 2.20.1 
    react: 0.0.0-experimental-3310209d0 => 0.0.0-experimental-3310209d0 
    react-dom: 0.0.0-experimental-3310209d0 => 0.0.0-experimental-3310209d0 
    typescript: 4.1.5 => 4.1.5