Unexpected Paragraph Formatting Within a Div Container

[EMG]

Though HTML mode in WordPress allows for the user to add in their own CSS styling and HTML content formatting if necessary, its normal behavior also makes it auto-format paragraph breaks without the user's input of paragraph tags. This is EXPECTED behavior.

I have discovered that in this specific manner of formatting when writing a post or page (note the LACK of spacing between the div tag and the content and the multiple paragraphs):

<div>Insert FIRST PARAGRAPH here.

Insert SECOND PARAGRAPH here.</div>

The end result (both visually and looking at the source code) is that there is a MISSING opening paragraph tag at the beginning of the first paragraph right after the opening div tag.

IF the user adds their own spacing between the divs and the content, paragraph formatting with happen on its own, but if the user doesn't add in the spacing and starts the paragraphed content right after the div like in the example above, the first paragraph tag isn't automatically added in.

For a screenshot of the end result source code that is generated (with the missing opening paragraph tag), please see the attached file.

Cheers!

[EMG]

screenshot of the generated source code with the paragraph formatting error

[SergeyBiryukov]

Related: #849, #3007, #3833, #4857.

[nacin]

This appears to be a duplicate of #3833 and/or others. Let's get a unit test.

[jorbin]

Unit Tests from MikeHansenMe originally from #30142

[jorbin]

MikeHansenMe wrote some unit tests on #30142 for this. The above patch was originally written by him.