Re: [Gnu-arch-users] PyArch newbie observations/questions

[Aaron Bentley]

David Allouche wrote:
> > Well, it could be
> > def delta(self, from=tree_latest_revision(), to=tree_root(), output=None):
> >
> > With no arguments or with just "to" specified, it would behave like changes.
>
>
> I'll drop pedantic mode for a moment, you seem to mean (using my made up
> syntax, which avoids the ambiguities and bugs in your prototype):
>
>     arch.ArchSourceTree.delta
>         [from: Revision, default: self tree-revision]
>         [to: Revision|ArchSourceTree, default: self]
>         [output: DirName, default: /tmp/something then remove it]

No, I don't think it should be a member of ArchSourceTree.

> Let me hit again the nail about the the underspecified "output"
> argument. Omitting it only makes sense for CHANGES where there is an
> expected default dirname, or if there is a way to get the stdout result
> of the command, which your prototype does not provide.

Okay, I admit I want incremental output to go to stdout.  I disagree 
with defaulting to /tmp/something because it's not clear then whether it 
should be removed afterward

> Also putting the file in /tmp will probably annoy people who use /tmp
> over NFS. I know that's a stupid thing to do, but from what I can read
> here, there are a lot of stupid and weird setups around.

Well, there are environment variables folks can set if they don't want 
to use tmp.  I'm using mkdtmp, which should honour those lifestyle choices.

> Anyway, I'm not going to implement it or accept it that way. DELTA
> must be allowed to operate without a ArchSourceTree being available, so
> it must be a module-level funtion, regardless of additional arguments
> about symmetric polymorphism or mysticsm that I could come up with.

Okay.  I'll keep using tla delta directly until we can framework it 
properly.

> > >  1. CHANGES can save its output changeset under a default name in the
> > >     tree-root, named after the master revision.
> >
> > True.  I'm not aware of a use for this, though.
>
>
> What about implementing alternative changeset serialization commands?

That would be valuable, but you'd want to know what the output directory 
name was, so you'd provide one.

> > >  4. CHANGES is used in different contexts than DELTA,

> > I think delta could be used in the same places just as conveniently, if 
> > it had sensible defaults.
>
>
> If your sensible defaults involve making delta a method of
> ArchSourceTree, I do not consider them sensible.

No, I (think I) meant it to be a free function.

> > The changeset output is nice to have for Pyaba.  To colorize it the 
> > right way, we'd need to parse the leading letters.
> Are you talking about the --diffs output or about the incremental output
> (where the leading letters are indeed important)?

Incremental output.

> > > That could be supported using an extended version of
> > > arch.util.StringOutput (passed as a keword argument to
> > > arch.WorkingTree.changes and arch.delta), but that would need much more
> > > reflexion to get it right.
> >
> > It seems to me that we'd want a per change iterator.
>
>
> I was rather thinking about a more general mechanism for methods which
> provide incremental output one could want to monitor. For example
> library-add and changeset-applying functions.

Ah.  I don't rightly know how to handle those.  Sounds like a 
multithreaded thing to me.

> > I didn't even know Python lacked 
> > destructors 'till today.  I miss RAII already.
>
>
> There are destructors, they are just different from C++ dtors.

You know, the Python tutorial has certain features in common with the 
Arch tutorial.  I especially like the bit when it says there are no 
constructors or private methods.  And then goes on to describe __init__.

> This is the __del__ special method.
> http://docs.python.org/ref/customization.html#l2h-174

Thanks.

> > Here's a PyArch-specific issue.  I could ship pyaba with PyArch in a 
> > subdirectory.  I'd forward any revisions that affected PyArch to you, of 
> > course.
>
>
> For the time being, I think that's the way to go. We'll iron out
> specific issues later.

Okay, I've done it this way.  "pyaba--dist--0"  It includes aba too. 
This is laughably easy to install.  For development, I'm using separate 
trees, to keep my changesets untangled.

Aaron

--
Aaron Bentley
Director of Technology
Panometrics, Inc.