[PATCH python-hglib] Add feature to allow hglib user to get call backs for prompts and output

[Barry Scott]

> On 16 Oct 2016, at 15:36, Yuya Nishihara <yuya at tcha.org> wrote:
> 
> On Thu, 06 Oct 2016 17:52:38 +0100, Barry A. Scott wrote:
>> # HG changeset patch
>> # User Barry A. Scott <barry at barrys-emacs.org>
>> # Date 1475772736 -3600
>> #      Thu Oct 06 17:52:16 2016 +0100
>> # Branch hglib-gui-features
>> # Node ID 1ac3819a61527836d47f7cd6a113b194c307ffeb
>> # Parent  efc527cc43d7394a5bd0deb1d29c4307592f7528
>> Add feature to allow hglib user to get call backs for prompts and output.
> 
>> The cb prefix was choosen to avoid matching a hg long option name.
> 
> That seems fine. merge() already has "cb" argument.
> 
>> -    def rawcommand(self, args, eh=None, prompt=None, input=None):
>> +    def rawcommand(self, args, eh=None, prompt=None, input=None, cbout=None,
>> +                   cberr=None):
>>         """
>>         args is the cmdline (usually built using util.cmdbuilder)
>> 
>> @@ -173,9 +174,29 @@
>> 
>>         input is used to reply to bulk data requests by the server
>>         It receives the max number of bytes to return
>> +
>> +        cbout is a function that will be called with the stdout data of the command
>> +        as it runs.
>> +
>> +        cberr is a function that will be called with the stderr data of the command
>> +        as it runs.
>>         """
> 
> Do they need to be separate callbacks? I think prompt() can be extended to
> take "err" value as an optional third argument.
> 


There are 2 reasons to have the cbout and cberr call backs. For a push/pull that
does not prompt it provides the GUI with progress information clearly marked as
normal, cdout, and error, cberr. The output is also timely, no need to wait for the
command to complete.

When a prompt event happens I found that I cannot rely on figuring out what
the last prompt was without a timeline of calls to cdout and cderr.

For example cdout gets the “user:” prompt but cderr gets the “password:”.
(Why is “password:” sent to stderr? Bug? Feature?)

My code can see that the last message was “password:” on cberr and know
that a password response is required.

I did not change the interface to prompt as it is already used elsewhere and
with the addition of cdout and cderr I can ignore its parameters.

Adding err to the prompt call may, or may not, be useful in other use cases.

Barry