Add I18n support for :placeholder HTML option is passed to form fields

[agrobbin]

This is my first real contribution to the Rails source, so any and all feedback is appreciated!

I looked at #3674 (which appears to have been the implementation of #768), but since that was back in 2012, and there didn't appear to be any actual opposition to this addition, I'm giving this a shot against the latest master.

This adds full I18n support for the :placeholder HTML5 input/textarea attribute. It tries to mimic the label I18n support almost exactly, first checking helpers.placeholder, then falling back to object.class.human_attribute_name, then @method_name.humanize. It only attempts to check for I18n values if you pass the :placeholder option, as requested in the original PR.

Basic usage:

<%= f.text_field :post, :body, placeholder: true %>

will look up the I18n value in this order:

helpers.placeholders.post.body
activerecord.attributes.post.body
attributes.body

I thought about extracting the common pieces from this and the Label tag, but thought getting feedback on the first pass would make more sense.

[rafaelfranca]

Thank you for the pull request.

I like the proposal but I have mixed feelings about it. I know Simple Form already supports this feature and I'm sure we don't want to the default Rails form builder to become Simple Form.

@jeremy WDYT?

[rafaelfranca]

BTW, this is the Simple Form implementation

[jeremy]

Great first contribution, @agrobbin !

I'm not sure whether the form helper should be responsible for placeholder i18n either. It's already simple to placeholder: t(...), and that accounts for having different placeholders depending on the context, rather than global defaults for all object.attr.

That said, we do i18n on many other form helpers so it's disappointing that this one spot people rely on doesn't work like the others. Translating symbol values of placeholder: :... could be a nice way to address that.

[agrobbin]

The thought here was that a frequent pattern has become to replace labels with :placeholder attributes, providing something that takes less space on mobile sites while still giving context to the user about what to enter into the form field. That was my rationale behind having it mirror the label I18n functionality.

@jeremy your suggestion about translating symbol values, if I'm understanding you correctly, feels like it would be very redundant:

<%= f.text_field :post, :body, placeholder: :body %>

The main issue I've been dealing with in one of the new applications I've been working on is that I've had to continuously include something like this in my forms:

<%= f.text_field :post, :body, placeholder: Post.human_attribute_name(:body) %>

That just feels gross :)

[agrobbin]

Is there something I should be doing to update this new feature, or is this request still just something that you are contemplating @rafaelfranca @jeremy?

[jeremy]

I'm positive on it, since it matches label i18n.

The thing that puzzles me with this and label i18n:

helpers.placeholders.post.body
activerecord.attributes.post.body
attributes.body

Labels and placeholders usually aren't boilerplate text that's identical for every form. I expected to see this try a translation key scoped by the AV template first.

Given that label doesn't do this either, fine to match its behavior IMO. But I'd find this behavior frustrating!

[agrobbin]

Labels and placeholders usually aren't boilerplate text that's identical for every form. I expected to see this try a translation key scoped by the AV template first.

@jeremy I have a PR in the works that adds some other logic to label and can take a swing at this if you want!

[agrobbin]

I've rebased this off of the latest master and added a CHANGELOG entry to Action View. Should be good to go!

[jeremy]

@agrobbin This looks like the same implementation as label, but that's a bit different - it has both value and content.

For a placeholder, a string value needs to remain a literal string. A symbol value could be treated as an i18n key.

cc @georgeclaghorn

[agrobbin]

@jeremy 👍 I will issue a new PR with that change and regression tests included.

[agrobbin]

@jeremy this appears to already work as you state with the current implementation of the code. This test appears to pass no problem:

def test_text_field_placeholder_with_string_value
  with_locale :placeholder do
    assert_dom_equal('<input id="post_cost" name="post[cost]" placeholder="How much?" type="text" />', text_field(:post, :cost, placeholder: "How much?"))
  end
end

Am I missing something?

[agrobbin]

Ah, figured it out! It was working in tests because of how human_attribute_name works by humanizeing the supplied attribute. I've now made it explicit within the Placeholderablemodule to just stop if the passed value is a String. Issued a new PR at #16639.

[jeremy]

Great! Thank you @agrobbin ❤️

[Nowaker]

Nice feature. ...But how to omit it? I'm not able to pass an arbitrary value for the placeholder now. I can pass autofocus, class and other HTML attributes just fine, except for placeholder. This is not good. It would be OK if it used default wisely, and showed my content if there's no i18n entry.

= f.text_field :hostname, placeholder: 'Enter Machine Hostname (e.g. myapp.company.com)'

<input id="machine_hostname" name="machine[hostname]" placeholder="Com)" type="text">

[agrobbin]

@Nowaker this was an oversight of this PR, and was fixed as part of #16639. The next 4.2 beta should bring that functionality back!

[Nowaker]

@agrobbin Cool, thanks!

[frankhereford]

Thank you! This is super helpful!