With my experience with Rails 4.0.5 so far, to my own naivety, I found that the error message displayed in form is different from the normal Rails app. The root cause is that 'scaffold.css' is not included.
<div class="field">
<%= f.label :password %><br>
<%= f.password_field :password %>
</div>
<div>
<%= f.label :password_confirmation %><br>
<%= f.password_field :password_confirmation %>
</div>
<div class="field">
<label for="account_password">Password</label><br>
<input id="account_password" name="account[password]" type="password" />
</div>
<div>
<div class="field_with_errors"><label for="account_password_confirmation">Password confirmation</label></div><br>
<div class="field_with_errors"><input id="account_password_confirmation" name="account[password_confirmation]" type="password" /></div>
</div>
In the case that your app uses N mountable plugins, there are 1+2N sets of assets actully. For each plugin, there are 2, one is in app, the other is in test/dummy/app. Of course, the second one is for testing that your app would not be used. So there will be 1+N sets of assets to be used.
assets defined by plugin, will be used in app (by default?). I have not found so far the way to configure plugin assets to be used or forbidden. Help!
The css related is in plugin's app/assets/scaffold.css . Such as
.field_with_errors {
padding: 2px;
background-color: red;
display: table;
}
Way to heal is to edit application.css to add *= require 'scaffold'
J