tpl/tplimpl: Fix double-escaping in opengraph template

[jmooring]

• Do not escape HTML entities
• Use consistent formatting for title and description with opengraph, schema, and twitter_cards
• Improve readability of twitter_cards

Closes #12418

[bep]

I suggest we focus on fixing #12418 and not add other not obviously related.

I assume the HTML gets escaped the second time in

content="{{ . }}"

Where is the first escape?

Also, a test for #12418 would help.

[jmooring]

Where the escapes coming from?

Front matter:

description = "This is <em>emphasized</em> and this is **bold**, but it's been stripped."

Passing description through .RenderString renders the single quote to ’.
Passing that through plainify renders ’ to ’.

I can split this into three PR's each with their own issue:

1. Fix Twitter og:description doubly escaped by Hugo 0.125.x #12418
2. Fix the same problem with Page.Title, Site.Title, and Site.Params.title in the opengraph template (Add plainify to Title - in internal template opengraph.html #8698)
3. Fix the same problems in schema.html and twitter_cards.html, and improve readability of twitter_cards.html at the same time

I will add a test for #12418, and add additional conditions to that test with each subsequent PR.

Believe me, I am as fatigued by this as you are.

[bep]

Passing description through .RenderString renders the single quote to ’.

.RenderString wasn't in the template before this PR, was it? Where is the double escape in the below?

{{- with or .Description .Summary site.Params.description | plainify }}
  <meta property="og:description" content="{{ . }}">
{{- end }}

Using Markdown syntax in title: e.g. sounds foreign to me and adding .RenderString all over the place is something we need to discuss. I have been known to overthink things in the performance department, but .RenderString isn't particulary light weight.

I suggest that we fix the bug with as little change as possible. People can create their own templates if they need special things.

[chalin]

Thanks for fixing this @jmooring!
See inline for one nit.

[jmooring]

@bep

Where is the double escape in the below?

When og:description is derived from .Summary, either automatic or with summary divider, e.g.

---
title: p1
---

Test line with a single quote: can't.
<!--more-->

There are three test cases that I need to include, with examples here:
#12418 (comment)

We've got way too many ways to define Summary, each with their own idiosyncrasies:
#8910 (comment)

[bep]

@jmooring OK,

So,

{{- with or site.Title site.Params.title | plainify | htmlUnescape }}

Etc. should work (??) and is perfectly fine.

Adding .RenderString to the mix needs a discussion (it will certainly slow down asciidoc builds ...)

[jmooring]

OK, we pass markdown through un-rendered. To handle the manual summary divider in one of the (now) 5 test cases, we need to chomp the trailing newline:

{{- with or site.Title site.Params.title | plainify | htmlUnescape | chomp }}

Hopefully that's OK.