Re: Shell completion on w32 uses "/" instead of "\"

[Lennart Borgman]

Kevin Gallagher wrote:
> I just got finished reading through this thread and, I must say, I'm a 
> bit puzzled by its continued limited focus to the question of "To 
> backward slash or not to backward slash?" in an Emacs shell window 
> running cmd.exe (or equivalent) on w32.  Instead, this discussion would 
> benefit greatly by taking several steps backward and looking at the 
> overall command line behavior in cmd.exe, with the goal of devising an 
> overall strategy for Emacs.  There is a need to determine to what extent 
> should Emacs support cmd.exe syntax and behavior in its support for 
> running cmd.exe in a shell window.
>
> So, let's take a look at some of the cmd.exe input syntax.  Some it is 
> is rather strange, by the way, and some of it is quite unexpected.  For 
> example, sometimes delimiters are needed between a command and the first 
> parameter, but other times they are not needed.  For example, ">cd ..", 
> with a space delimiter, and   ">cd..", without a space delimiter are 
> both accepted by the parser as valid.  Press return and both are move 
> the current directory up one level.  However, enter ">cd." followed by a 
> <TAB> and the bell rings, even though ">cd.." is valid.
>
> Suppose the current directory contains 5 directory entries called "aa", 
> "bb", "cc", "dd one", and "eleven ee".  Enter "cd" at prompt and then 
> press <TAB>, the bell rings.  Enter "cd", followed by a space, and then 
> press <TAB>, the first directory, in the current directory, is displayed 
> next to "cd" like this:
>
>     cd aa
>
> Press <TAB> again and the line is re-written as
>
>     cd bb
>
> <TAB> again and we have
>
>     cd cc
>
> again,
>
>     cd "dd one"
>
> again,
>
>     cd "eleven ee"
>
> and again,
>
>     cd aa
>
> cycling back through the list.  It makes no attempt to continue command 
> completion into a subdirectory.  To make this happen, the user must 
> enter a backward slash after the directory name and then press <TAB>.


Yes, you are right. This behaviour is not mirrored at all in Emacs shell.


> Now, here's a surprise!  Suppose "aa" has a subdirectory "xy" and "xy" 
...


I do not think cases outside of what cd is specified to do in cmd.exe 
are important.


> Nevertheless, if, instead, I wrap the parameter input to "dir" in double 
> quotes like this
>
>     E:\kg\aa>dir "xy/zz"
>
> then cmd.exe accepts this and generates a directory listing of 
> "E:\kg\aa\xy\zz"!


This is not specified to work. I found some surprises there too before.


> This leads me to suggest that, instead of "To backward slash or not to 
> backward slash?", perhaps the question should be "To double quote or not 
> to double quote?"  Of course, we have to remember that this applies to 
> "dir" but not "cd", though "cd" will accept the double quotes.  I 
> haven't tested this syntax with other commands, such as "copy", "xcopy", 
> etc.  But, hopefully, you get the point:  cmd.exe has a very strange 
> input syntax parser with unexpected and inconsistent behavior in what it 
> is willing to accept as valid input syntax.
>
> The behavior of cmd.exe, when <TAB> is pressed, is quite different from 
> what Emacs attempts to do for the user.  Technically, one could argue 
> that, for cmd.exe, Emacs should append nothing to a directory completed 
> by <TAB>. 


It would make a very bad impression I think.

> I think I've made the case that the support Emacs should provide when 
> running cmd.exe in a shell window is complicated and very messy; too 
> messy to deal with now.  I vote we let it be until after Emacs 22 is 
> released.


Then we will just leave that bug there for a long period. I think that a 
combination of long periods between releases and leaving bugs is not so 
very good. And unfortunately it is a bug on w32, that in one sense is a 
platform where we want to attract people because it makes it easier to 
switch to GNU/Linux later.

BTW, I found the directory sync in shell is not working so good for me. 
Is there something that prevents that comint sends a pwd and reads the 
result before trying to TAB file name expansion?