Update regex of italic

[dukenv0307]

Details

When entering ___ (3 underscores), the italic characters (underscores) got parsed and only leave one underscore after parsed.
It has 3 changes compared to the current italic regex we're using:

• Replace (?!\s) by (?![\s_]), so that it doesn't match _ at the beginning of the content

• Replace \S by [^\s_], so that it doesn't match _ at the end of the content

• Replace the word boundary \b by a regex at the beginning and end ([^\W_]?) and (?![^\W_]) so that the word boundary will also exclude the _ as word, so that cases like content and content will work correctly.

Also we need to update this replacement so that it will not replace if the match starts with a word character (this logic works with ([^\W_]?))

Fixed Issues

$ Expensify/App#17665
PROPOSAL: Expensify/App#17665 (comment)

Tests

To test, we need to update the hash commit of expensify-common package in App repo into 6a781aa8f027d87f78e5dd808759795631fc30e5 like this:
"expensify-common": "git+ssh://git@github.com/Expensify/expensifycommon.git#6a781aa8f027d87f78e5dd808759795631fc30e5"

Open any chat and send these messages and verify that

1. ___ --> Verify that this message isn't parsed
2. _italic__ --> Verify that this message is parsed
3. __italic_ --> Verify that this message is parsed
4. _italic_another_italic_ --> Verify that this message is parsed
5. _italic_ --> Verify that this message is parsed
6. s_italic --> Verify that this message isn't parsed
7. italic_s --> Verify that this message isn't parsed

_italic

italic
italic_

--> Verify that this message is parsed
9.

_
_
_

--> Verify that this message isn't parsed
10.

_
_test
_

--> Verify that this message isn't parsed

• Verify that no errors appear in the JS console

Offline tests

QA Steps

1. Open any chat
2. Send these messages and verify that
   ___ --> Verify that this message isn't parsed
   _italic__ --> Verify that this message is parsed
   __italic_ --> Verify that this message is parsed
   _italic_another_italic_ --> Verify that this message is parsed
   _italic_ --> Verify that this message is parsed
   s_italic --> Verify that this message isn't parsed
   italic_s --> Verify that this message isn't parsed

• Verify that no errors appear in the JS console

Screenshots/Videos

Web

Mobile Web - Chrome

Mobile Web - Safari

Desktop

iOS

Android

[github-actions]

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[dukenv0307]

I have read the CLA Document and I hereby sign the CLA

[dukenv0307]

recheck

[parasharrajat]

@dukenv0307

• Please add more tests for multiline syntax.
• Add unit tests for the new changes to the regex.

Do you think we should also update the bold regex?

[dukenv0307]

@parasharrajat Thanks so much for your reminder. I just updated, please help to check again

[parasharrajat]

@alex-mechler can you please trigger checks?

[parasharrajat]

@dukenv0307 I will suggest that you create the PR on the Expensify/APP repo and use the latest commit hash from this PR. We can test it meanwhile this is being reviewed and merged. Once this is merged, we can update the hash there and close that as well. This will speed up the process.

[dukenv0307]

@parasharrajat The PR in App repo is ready

[parasharrajat]

LGTM.

[alex-mechler]

I don't think we need this capture group here. We aren't doing anything with the captured characters, and it would let us avoid changing the replacement. The test suite passes locally, and it captures the same test strings mentioned in the issue without this group

Suggested change

	regex: /(?!_blank")([^\W_]?)_((?![\s_])[\s\S]*?[^\s_])_(?![^\W_])(?![^<]*(<\/pre>|<\/code>|<\/a>|_blank))/g,
	regex: /(?!_blank")[^\W_]?_((?![\s_])[\s\S]*?[^\s_])_(?![^\W_])(?![^<]*(<\/pre>|<\/code>|<\/a>|_blank))/g,

[dukenv0307]

@alex-mechler I updated and tested again, it works well. Also updated new hash in App repo. Please help to check again.
cc @parasharrajat

[alex-mechler]

LGTM and tested well, thanks for the quick updates!

[alex-mechler]

Going to merge this since @parasharrajat had already approved