Remove extra inner linebreak from code blocks

[jrylan]

Description

• Fixes
  Currently, marked adds a line break before inserting </code></pre>, some highlighting and parsing tools I've ran into actually interpret this line break (since it's wrapped in a <pre>) as an extra line break that should be displayed in the output.

Essentially the following HTML from marked:

<pre><code class="language-js">const foo = 'bar'
</code></pre>

Will produce rendered output with some highlighters as having an extra trailing inner line break:

const foo = 'bar'

Expectation

(no trailing inner line break)

<pre><code class="language-js">const foo = 'bar'</code></pre>

Then highlighters will render correctly as:

const foo = 'bar'

Contributor

• Test(s) exist to ensure functionality and minimize regression (if no tests added, list tests covering this PR); or,

Committer

In most cases, this should be a different person than the contributor.

• Draft GitHub release notes have been updated.
• CI is green (no forced merge required).
• Merge PR

[UziTech]

LGTM

[jrylan]

Forced a new commit that removed marked.min.js from my changes.

[styfle]

Nice!

[styfle]

@remyrylan Thanks for the contribution!

[hail2u]

I think both CommonMark spec and GFM spec say last line break should be left as it is. It is a highlighter bug, not marked or spec bug. It must be reverted.

[styfle]

@hail2u Which example number in the spec are you referencing?

[hail2u]

Example 109 is most clear. This 1 line fenced code block has line break. Also commonmark.js dingus can reproduce this behavior.

[styfle]

This is a bit strange since the spec doesn't seem to call it out directly. Only the example html output (and consequently the dingus) show this "feature".

Example 99 seems to avoid adding a newline.

Example 109 seems to add a newline.

Our tests show both 99 and 109 as passing but I would expect one to pass and one to fail.

@UziTech Is this due to the way html-differ works?

[UziTech]

Most likely an html-differ bug.

@hail2u why is this a problem, that the last line break is missing? Did you run into a specific case where adding the line break would be beneficial?

[hail2u]

To be honest, there is no big problem here. Some syntax highlighter shows ↲ character just before line break like GUI text editors. With an HTML rendered by marked v0.5.0, they failed to show last ↲ because there is no last line break. But this is a little problem.

I think the problem mentioned in this issue is also a little problem. The original markdown, CommonMark, GFM, and marked prior to v0.4.0 leave the last line break as it is. It would be a reasonable and a safest behavior, isn’t it? Markdown has been used for a long time, there might be a tool that depends on this behavior.

---

I find a clear rule about this line break from the CommonMark spec - 4.4 Indented code blocks:

... The contents of the code block are the literal contents of the lines, including trailing line endings, ...

[Feder1co5oave]

The passing tests are because of this bug in html-differ.
My fork should fix this. Try it out and see what goes wrong.