question about text formatting in Vim

I'm usi开发者_Go百科ng Vim to write text that isn't code, just free form writing. To do this I like to have formatoptions include the w flag and sometimes the a flag.

The w flag is supposed to make it so an end-of-paragraph occurs when a line ends in a non-blank character, rather than at first blank line (which is Vim default). Here is snippet from the help docs:

w   Trailing white space indicates a paragraph continues in the next line.
    A line that ends in a non-white character ends a paragraph.

The a flag makes reformatting automatic, as you type. For example, in document with text below and w and a flags the lines reformat as I type only up to the 'last line in paragraph' and not below.

This it the first line of the paragraph. <cr>
The text in it reformats properly as I type <cr>
up to the last line of the paragraph, which is <cr>
right after this line, that is, just below here: <cr>
This is the last line of paragraph.<cr>
This is the first line of second paragraph. <cr>
Even though there is no blank line between <cr>
it and first paragraph, any reformatting of <cr>
the first paragraph ends at the last line <cr>
of first paragraph.<cr>
<cr>
This the the first line after second paragraph<cr>

Now to my question: With a and w flags the reformatting works properly as I type in the first paragraph, i.e, second paragraph remains untouched. But sometimes I want to select the current paragraph using vap. It seems to me that with the w flag set this should select only the first paragraph. But in fact issuing vap in first paragraph selects the second paragraph also, all the way down to the blank line with <cr>, seemingly ignoring the w formatoptions flag.

Is this expected behavior? Am I missing something? Why does vap not select only the paragraph I'm in, which ends at first line with no trailing whitespace?

If you read the help at :h paragraph this does not mention the 'fo' setting. So it looks like the fo setting does not really change, what defines a paragraph. This might be a bug or unclear documentation, so you might want to discuss this on the vim-dev mailinglist.

From :help text-objects or :h paragraph you can see that a paragraph for vim begins after each empty line, and also at each of a set of paragraph macros, specified by the pairs of characters in the 'paragraphs' option. Blank lines containing only whitespace are also paragraph boundaries.

The w flag in formatoptions only makes a difference when autoformatting a paragraph as you type: it will split lines and leave whitespace at the end of lines which do not end a paragraph. I suppose the help text is a bit confusing.