OmniAuth and Devise, how to set optional passwords

I am using OmniAuth and Devise to authenticate users. I would like users that have signed up using OmniAuth providers to be able to set an optional password (needed for API authentication) but I'm running into a wall.

If a user creates an account via OmniAuth and tries to set a password they get the following error:

BCrypt::Errors::InvalidHash in Re开发者_StackOverflow社区gistrationsController#update

I believe this is because the password is blank. What's a good way around this? I've thought about generating a random password but the problem with that approach is the user needs to know the current password in order to edit settings.

Edit: I looked at allowing the user to change settings without requiring a current password and that's what I would like to do only if the user didn't have a password initially.

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An alternative is to add the following into your 'user' model class to bypass password verification if there is no password to verify, where provider is some field that is set when using external authentication.

def valid_password?(password)  
  !provider.nil? || super(password)  
end

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I assume you don't want the easy way out which would be to simply reset the password if they wanted to set it?

user.send_reset_password_instructions

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This comes a bit late but it might help someone else, with Andrew's answer you can in create a password and store it in the database, but you can't login using your email and your new password, solved this by setting:

  def valid_password
    !provider.nil? && !encrypted_password.present? || super
  end

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Another alternative. You don't have to include a new field. Just catch the exception raised and return false. Here is the code.

def valid_password?(password)
   begin
      super(password)
   rescue BCrypt::Errors::InvalidHash
      return false
   end
end

This should do the job.