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On 14-Mar-2015 15:34, Bram Moolenaar wrote:
>
> Ingo Karkat wrote:
>
>> On 14-Mar-2015 02:11, James McCoy wrote:
>>> On Fri, Mar 13, 2015 at 09:54:18PM +0100, Ingo Karkat wrote:
>>>> it's possible to avoid escaping a "[" character:
>>>>
>>>> ,----[ :help E769 ]---- | When the ']' is not there Vim will
>>>> not give an error message but | assume no collection is used.
>>>> Useful to search for '['. `----
>>>>
>>>> But when using that feature in a :substitute command, the
>>>> replacement part is mistakenly added to the pattern:
>>>>
>>>> :s/[//g E486: Pattern not found: [//g
>>>
>>> No, that's not what's happening. You can leave off the entire
>>> replacement and the delimiter before it. When this happens,
>>> Vim treats it as deleting the matching strings. To quote:
>>>
>>> If the {string} is omitted the substitute is done as if it's
>>> empty. Thus the matched pattern is deleted. The separator
>>> after {pattern} can also be left out then. Example: >
>>> :%s/TESTING This deletes "TESTING" from all lines, but only one
>>> per line.
>>
>> Right. My point is that because the "/" delimiters are not
>> actually left off (they are there, in the correct, unescaped
>> form), the :s command *mistakenly* runs into the case you've
>> quoted. Putting it yet another way, the "[" consumes the
>> following characters (including the unescaped separators),
>> assuming they belong to the collection, and when at the end the
>> collection isn't closed, the parsing should backtrack and
>> reinterpret, but it currently doesn't.
>
> I understand that this is confusing, but it's working as
> documented.
I don't see this particular behavior documented. I would expect
something like this (highlighting the current inconsistencies):
"An unclosed [ will do a literal search, but when such pattern is
directly included in a :substitute command (but not when such pattern
is reused from the last search via :s//...), the remainder is
interpreted as the pattern; i.e. you cannot add a replacement part and
:s_flags there.
> The alternative, detecting the unclosed [ in some circumstances,
> will make it less consistent and probably even more confusing. So
> let's just leave it as it is.
I've never argued for that. Of course, the unclosed [ would have to be
detected in _all_ circumstances. That shouldn't be too difficult; the
regexp engines already do that.
> It's clear that if you type the wrong command things may go wrong.
I don't think :s/[/x/g is wrong. It simply parses as pattern=[,
replacement=x, flags=g. Unfortunately, Vim's implementation is buggy
and parses it as pattern=[/x/g replacement= flags= (because the [...]
collection parsing suspends the delimiter parsing until the closing ],
but this isn't a collection, so it shouldn't apply!)
If I had wanted that, I would rather type :s/[\/x\/g (or
:s/[\/x\/g//), i.e. properly escape the / delimiters.
> That's what we have undo for.
As I said, I'm mostly worried about plugins blindly putting @/ into
the :substitute (maybe with prepending / appending something else, and
then failing due to the inconsistency caused by the bug. That would be
hard to detect by the user; undo wouldn't help much.
I'm all for consistency, and fixing this bug would IMO increase that,
so that the special case of unclosed [ and the :s/// separators
interact in a benign way. I was motivated to report this because one
Vim user was struggling with just this, and went to Stack Overflow to
ask for help.
- -- regards, ingo
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