Email textfield is not enabled when `allowNewEmailAccounts` is set to `NO`

[tikipatel]

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Step 1: Are you in the right place?

Yes.

Step 2: Describe your environment

• Objective C or Swift: Swift
• iOS version: iOS 13
• Firebase SDK version: Unrelated
• FirebaseUI version: 8.4.0
• CocoaPods Version: N/A

Step 3: Describe the problem:

When using FUIEmailAuth where allowNewEmailAccounts is set to NO, the user is unable to tap the email textfield to enter an email.

Steps to reproduce:

1. Instantiate an instance of FUIEmailAuth with allowNewEmailAccounts as NO
2. Instantiate an instance of FUIAuth and add the above as a provider
3. Run the app and tap Sign in with email

Observed Results:

• Unable to enter email address.

Expected Results:

• Should be able to enter email address.

Relevant Code:

https://github.com/firebase/FirebaseUI-iOS/blob/master/EmailAuth/FirebaseEmailAuthUI/FUIPasswordSignInViewController.m#L262

I think that cell.textField.enabled should only be NO when the _email property of the FUIPasswordSignInViewController class is non-null.

For a better experience, the email textfield should always be enabled in case the user wants to use a different email to sign in.

[morganchen12]

The fix for this has been released.