Support defining text nodes directly in the root document

What does this MR do and why?

• NOTICE: This change is behind a the preserve_unchanged_markdown feature flag.
• Context: This change is part of a larger effort to preserve unchanged Markdown in the Content Editor. For this effort, we need to support client-side parsing of Markdown content.

This MR fixes a bug in the Content Editor’s client-side Markdown parser where text nodes that are direct children of the root document make the AST to ProseMirror document fail. The bug is fixed by wrapping those text nodes in a paragraph. This is what a text node looks like when it is a direct child of the root node:

{
  "type": "root",
  "children": [
    {
      "type": "html",
      "value": "<i class=\"foo\">\n  *bar*\n</i>",
      "position": {
        "start": {
          "line": 1,
          "column": 1,
          "offset": 0
        },
        "end": {
          "line": 3,
          "column": 5,
          "offset": 28
        }
      }
    }
  ],
}

That AST represents the Markdown snippet in example 164 of the Commonmark spec: https://spec.commonmark.org/0.30/#example-164

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Edit or create a Wiki page
2. Enter the following Markdown snippet in the Classic Markdown Editor. The example comes from the Markdown spec: https://spec.commonmark.org/0.30/#example-164

   <i class="foo">
     *bar*
   </i>

3. Switch to rich text mode. You should see the same result as the screenshots above.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

changed milestone to %15.1

added feature flag featureenhancement frontend groupeditor [DEPRECATED] typefeature labels

assigned to @ealcantara

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	1 Warning
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Reviewer roulette

Changes that require review have been detected!

Please refer to the table below for assigning reviewers and maintainers suggested by Danger in the specified category:

Category	Reviewer	Maintainer
frontend	Fernando Arias (@farias-gl) (UTC-5, 1 hour behind @ealcantara)	Olena HK. (@ohoral) (UTC+3, 7 hours ahead of @ealcantara)

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Generated by Danger

Bundle size analysis [beta]

This compares changes in bundle size for entry points between the commits 9dc66dd1 and 188d97ee

Special assets

Entrypoint / Name	Size before	Size after	Diff	Diff in percent
average	3.46 MB	3.46 MB	-	0.0 %
mainChunk	1.94 MB	1.94 MB	-	0.0 %

---

Note: We do not have exact data for 9dc66dd1. So we have used data from: b1f0ef03.
The intended commit has no webpack pipeline, so we chose the last commit with one before it.

Please look at the full report for more details

---

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changed title from Allow text nodes inside the root document to Support defining text nodes directly in the root document

changed the description

@thomasrandolph: Could you review this MR, please?

requested review from @thomasrandolph

Allure report

allure-report-publisher generated test report!

review-qa-blocking: test report for 188d97ee

expand test summary

+-------------------------------------------------------------------+
|                          suites summary                           |
+----------------------+--------+--------+---------+-------+--------+
|                      | passed | failed | skipped | flaky | result |
+----------------------+--------+--------+---------+-------+--------+
| Plan                 | 41     | 0      | 1       | 41    | ❗     |
| Verify               | 12     | 0      | 1       | 12    | ❗     |
| Manage               | 36     | 0      | 2       | 38    | ❗     |
| Create               | 23     | 0      | 2       | 23    | ❗     |
| Package              | 0      | 0      | 1       | 0     | ➖     |
| Protect              | 2      | 0      | 0       | 2     | ❗     |
| Version sanity check | 0      | 0      | 1       | 0     | ➖     |
| Configure            | 0      | 0      | 1       | 0     | ➖     |
+----------------------+--------+--------+---------+-------+--------+
| Total                | 114    | 0      | 9       | 116   | ❗     |
+----------------------+--------+--------+---------+-------+--------+

Setting label(s) devopscreate sectiondev based on ~"group::editor".

added devopscreate sectiondev labels

approved this merge request

requested review from @xanf and removed review request for @thomasrandolph

@thomasrandolph, thanks for approving this merge request.

This is the first time the merge request is approved. To ensure full test coverage, a new pipeline has been started.

For more info, please refer to the following links:

• rspec minimal jobs
• jest minimal jobs
• merging a merge request.

resolved all threads

approved this merge request

enabled an automatic merge when the pipeline for 96a484cc succeeds

aborted the automatic merge because source branch was updated

added 113 commits

• 026fed4c...9dc66dd1 - 112 commits from branch master
• 188d97ee - Allow text nodes inside the root document

Compare with previous version

merged

mentioned in commit 7dc2ba2c

added workflowstaging-canary label

added workflowcanary label and removed workflowstaging-canary label

added workflowstaging label and removed workflowcanary label

added workflowproduction label and removed workflowstaging label

mentioned in issue gitlab-com/www-gitlab-com#13386

added releasedpublished label

added releasedcandidate label and removed releasedpublished label

mentioned in merge request gitlab-com/www-gitlab-com!135591