Paste: Remove HTML Formatting Space

[ellatrix]

Description

Fixes #13497. (Alternative to #17459. This is a more general solution to work with any source and any block type, so it also fixes the following issues:)
Fixes #17302.
Fixes #14298.
Fixes #13647.

In HTML, there are a few characters you can use to format the code (indent, make it pretty etc.): \n, \t and normal spaces. We don't want our paste output to have these characters. Sequences of these characters should be removed, or replaced with a single normal space if it is a meaningful space (in other words, part of the content).

To do: write unit tests.

How has this been tested?

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.

[tfrommen]

Hm, I think this should work for the MS Word issue (see #17459), too.

Could we maybe add something like these two sample paragraphs to the MS Word fixture, though?

[ellatrix]

@tfrommen I think https://github.com/WordPress/gutenberg/pull/17470/files#diff-d84fbca4bbde019dae6d0aa82778e23c should account for that.

[ZebulanStanphill]

Does this account for <pre> elements, where whitespace is expected to be considered as part of the content?

[ellatrix]

@ZebulanStanphill that’s a good catch! I’ll disable it in pre elements.

[tfrommen]

Hm, somehow I thought this would be specific to certain destinations, like MS Word, Google Doc, whatever. But now I see that this is running always.

In that case, there are more use cases where line breaks are to be left alone, for example, the content of a <textarea />.

I understand the reasoning behind this PR, but, for now, I would really love for the other, much more focused PR, #17459, to get merged. 😶
If some other change later on accounts for what my PR is doing for MS Word only, it can easily be removed.

[ellatrix]

Form elements like textarea won't get pasted. I think this is the right direction to go.

[yankiara]

Hi,
How can we help speeding up this merge?
I'm willing to test/review/do anything to commit.
Yan

[aduth]

There's a test failure which appears it could be legitimate (failing test/integration/blocks-raw-handling.test.js).

[ellatrix]

@aduth Fixed in the last commit.

[aduth]

I'm not 100% confident that this is following the previously-mentioned specification, especially with regards to:

Any sequence of collapsible spaces and tabs immediately preceding or following a segment break is removed.

https://www.w3.org/TR/css-text-3/#white-space-phase-1

...which isn't really explicitly handled here. But it does seem to work as expected with everything I've thrown at it.

[ellatrix]

I'm not 100% confident that this is following the previously-mentioned specification, especially with regards to:

Any sequence of collapsible spaces and tabs immediately preceding or following a segment break is removed.

https://www.w3.org/TR/css-text-3/#white-space-phase-1

...which isn't really explicitly handled here. But it does seem to work as expected with everything I've thrown at it.

Yeah, this is a simplified version. We can make adjustments if it's not enough. Tabs are replaced with spaces, which are preserved or removed depending on the context.

[dmsnell]

\f (form feed) is also allowed here, though rare in practice.