Regression: Code syntax not rendering or highlighting as expected in markdown

Description

Code blocks are not rendering syntax highlighting and hover tag as expected, when the opening backticks specify syntax to use. For example, posting the following just renders as a plain code block:

Regression; does not repro on v5.15.3. Repros on v5.17 release branch (and curiously also on v5.16.3, though this test did not raise any issues during v5.16.0 release testing).

QA Test Steps

1. On browser or desktop app, on a server with test command enabled (such as postgres.test), post the following:
/test url test-syntax-highlighting

Observed: All render as simple code blocks, without highlighting or expected formatting. Code tag also missing on hover

Expected: Each renders with specific highlighting and code tag on hover

Note: Can also copy raw content from https://github.com/mattermost/mattermost-server/blob/master/tests/test-syntax-highlighting.md and post it, if test command is not enabled on the server you're testing on, or post the following to just test one of the examples:

``` diff

  •  

    •  

      • /path/to/original ''timestamp''

      • /path/to/new ''timestamp''
        ***************

      • 1 ****
        ! This is a line.

      • 1 —
        ! This is a replacement line.
        It is important to spell
        -removed line
        +new line
        ```

Status

Mana

None

Assignee

Harrison Healey

QA Assignee

None

Reporter

Linda Mitchell

Epic Link

None

Fix versions

Mattermost Team

Apps

Sprint

Labels

QA Testing Areas

Markdown

GitHub Issue

None

Components

None
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