ModernGov template page generation module

[Adnan-cds]

Second incarnation of the Modern.Gov template page module. I have polished up Eke's original code by:

• Using "localgov" prefixes.
• Used a simpler controller that does nothing other than producing an empty page. But then allows us to use a custom page template to control the page content.
• As discussed, used DOM-based URL replacement instead of string replacement. Turned out Drupal\Component\Utility\Html::transformRootRelativeUrlsToAbsolute() only acts on the body part of an HTML document instead of the entire document, so had to lift its code and tweak as necessary.

Recap

To serve as a ModernGov template, a page needs to meet two requirements:

• Uses these tokens in appropriate locations within the page:
  • {pagetitle}
  • {breadcrumb}
  • {content}
  • {sidebar}
• Uses absolute URLs instead of relative URLs.

How to test

• Install the localgov_moderngov module. It's not in packagist.org yet. So you will have to grab it from Github.
• Verify the presence of the Modern.Gov tokens (e.g. {pagetitle}) in the page.
• Verify link and asset URLs within the HTML page source. These should all be absolute URLs.

Remaining issue

While testing, realized that any relative URL sitting inside embedded Javascript (e.g. drupalSettings) won't change to absolute URL. Not sure how big a problem that is.

[finnlewis]

Discussing this in Merge Monday call.

@Adnan-cds points out that inline javascript in the head is not covered by the current approach to search and replace convertion of relative to absolute URLs.

@ekes wonders if there's a way to hook into the libraries attach process to convert urls.

See https://democracy.croydon.gov.uk/uuCoverPage.aspx?bcr=1 for example of ModernGov in action.

Caching is also an issue. For blocks that are cached, with relative links, these need to be rendered differently depending on whether they are on the ModernGov system or on Drupal.

Next steps on this:

• @Adnan-cds will try the suggestion from @ekes to hook into the libraries.

[markconroy]

From a frontend/template perspective this looks fine to me.

Once commited/merged, I'll create a corresponding template for the localgov_base theme that adds our specific markup so we can support this out of the box.

[Adnan-cds]

will try the suggestion from @ekes to hook into the libraries.

Here are my thoughts so far: From hook_page_attachments_alter(), we can inspect all attachments. The relevant ones for URL conversion are of two types:

• drupalSettings items
• html_head items where ['#type' => 'html_tag', '#tag' => 'script']

The problem now is, there is no clear pattern for any relative URL within the above two. For example, we may have something like this:

$attachments['drupalSettings']['foo'] = [
  'zero' => '/i/am/a/path',
  'src'   => '/i/am/also/a/path',
]
$attachments['html_head']['bar'] = [
  '#type' => 'html_tag',
  '#tag'   => 'script',
  '#value' => 'var a_path = "/yet/another/path"; do_something(a_path);'
]

As you can see, there is no easy way to identify who is a relative path and who is not unless you are looking for an exact string pattern such as 'a_path = "/yet/another/path"' which is easy for a site specific custom module, but not in a contrib module.

Any hints are welcome. @finnlewis @ekes @andybroomfield @markconroy

[finnlewis]

Notes from Merge Monday today:

• @Adnan-cds explored ways to re-write inline Javascript, but there is no easy way.

Happy to push ahead with this and document the limitations in the README. (Already noted here https://github.com/localgovdrupal/localgov_moderngov/blob/1.x/README.md#good-to-know)

[Adnan-cds]

Thanks for all the approvals. I am merging...