Saving a block with backslash in RichText wipes out all RichText data within the block

[Alexius08]

Describe the bug
Inputting backslashes into RichText components inside a PHP-rendered block results into loss of saved data inside all RichText components within the affected block.

To reproduce
Steps to reproduce the behavior:

1. Make a minimum variable block with at least two RichText input components and render it using PHP.
2. Use the block on a post, set the value of the RichText components to normal strings and save it.
3. Refresh the post editor for the post with the block and replace the contents of one of the RichText components with at least one backslash.
4. Preview to see the value of RichText-dependent attributes within the block reduced into empty strings. Save to overwrite all values with empty strings.

Expected behavior
Normal behavior is preserving all values of RichText-dependent attributes even when the backspace-filled string is inputted.

Screenshots
PHP-rendered block with two RichText inputs filled with normal values, as seen in the editor.

PHP-rendered block with two RichText inputs filled with normal values, as seen in the preview.

PHP-rendered block with two RichText inputs, one of them filled with only backslashes, as seen in the editor.

PHP-rendered block with two RichText inputs, one of them filled with only backslashes, as rendered in the preview. Saving the post at this state leads to removal of all data in the RichText inputs.

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: Wordpress 5.2.2, PHP 7.2.9

[ehti]

Able to reproduce this! Thanks for the report @Alexius08

For easier testing, we can also use the Search block instead of creating a new block. Title in the search block is RichText and rendered in PHP.

1. Add search block to a post
2. Change the title from Search to ABC\. Save draft
3. Refresh the page
4. Title will be gone and it gets reset to just Search

(Backslashes are a problem).

Also ref https://wordpress.slack.com/archives/C02QB2JS7/p1576127699440400

[skorasaurus]

Hi,

I'm still able to reproduce this as of Gutenberg 13.2.; note that this only occurs if the last character in the saved attributed is a backslash;

for example, in the test case above by @ehti ; if you change the title in title block to "search for records and\or data" ; the attribute will be saved ;but if you finish it as ABC\ it will not.

[dmsnell]

@Mamaduka @youknowriad to be clear and get it out of the way, this isn't related to the recent type: 'raw' change is it?

[youknowriad]

@dmsnell I don't think so as that change is only applied to some blocks not all RichText blocks and this bug is about a custom block with two rich text elements.

[dmsnell]

thanks @youknowriad - I can imagine some plausible ways this could go wrong.

Can we get a copy of before/after post_content/HTML for these posts when the error is present?

[Mamaduka]

The search button text has a type: 'string'. This is what block HTML output looks like when I add a backslash at the end of the string.

Edit: I can only reproduce the issue when the string attribute is serialized in the block comment.

<!-- wp:search {"label":"Search","buttonText":"Search \\u0022} /-->

Screenshot

[Mamaduka]

I believe this regression was introduced in #6619.