Are colons forbidden for TODO keywords?

[Tommy Kelly <tommy.kelly@verilab.com>]

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*Am I correct that colons are forbidden for TODO keywords (at very least as
the last character)? *
I can't see an explicit prohibition in the manual, or in
https://orgmode.org/worg/dev/org-syntax.html, but I'm seeing behavior that
suggests there perhaps should be, as follows.

So, for vaguely aesthetic reasons, I decided I'd like my TODO keywords to
end in colons. That is: TODO:, INPROGRESS:, DONE:, and so on; instead of
just TODO, INPROGRESS, DONE, etc. And it seemed to work fine. At very least
for things like cycling through sequences, quick selection, color and other
face attributes, and so on, there didn't seem to be any issue.

However I've just noticed that the colons do seem to be a problem for smart
tree construction. For example, if I run 'C-c / T' and provide "DONE:"
(with colon) as the keyword, no headlines are found, despite there being
many with that keyword in the relevant file. But if I provide "DONE" (no
colon)[1] as the keyword, then all of my "DONE:" (with colon) headlines are
found.

As I say, I can't find anything in the documentation saying that colons are
forbidden, but it's beginning to feel like it. Does that sound credible, in
which case does the documentation need a tweak? Or was there no intention
to restrict colon use, in which case is it the sparse tree construction
code that needs tweaked?

thanks,
Thomas

[1] Having first added "DONE" to org-todo-keywords, so as to allow it to be
a valid choice for 'C-c / T'

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