[Yum-devel] [PATCH]: allow plugins to add new commands to the cli

[Bastiaan Bakker]

On Tuesday 12 September 2006 18:52, Menno Smits wrote:
> Hi Bastiaan,
>
>  > While trying to reimplemnt yum-builddep as a plugin I noticed that it's
>  > not yet possible for a plugin to add new commands to the cli.
>  > Attached is a patch against HEAD that enables plugins to register new
>  > commands.
>
> Thanks for the patch. This has been a longstanding TODO that I've
> never gotten around to.
>
> I think the overall approach is good. Separating out doCommands into
> individual methods makes a lot of sense regardless and the new
> registerCommand() method fits in well with the rest of the plugin API.
>
> I'm not too keen on the struture of yum_cli_commands. The 'checks'
> attribute is a little klunky and inflexible. Why not just have the
> handler method for a command call checkRootUID/checkGPGKey/whatever
> as required? I think this would be much clearer. Plugins would have
> access to these check methods via the base object too.
>

Agreed. Sometimes when you start parameterizing stuff you can't stop :-)

> yum_cli_commands would then be simplified to something like:
>      {
>          'update': self.doUpdateMethod,
>          'install': self.doInstallMethod,
>          ...
>      }
>

Well, I separated the checks from the handler method in order to have all 
checks completed before cli.doCommands would be called. I assumed this is 
desirable, else why bother with a separate parseCommands method?

> Also there's a bug in registerCommand():
>  > +    def registerCommand(self, name, command, checks=[]):
>  > +        if self._base.yum_cli_commands is None:
>  > +           raise Errors.ConfigError('registration of commands not
>
> supported')
>
>  > +
>  > +        if 'command' in self._base.yum_cli_commands:
>  > +            raise Errors.ConfigError('Command "%s" already defined'
>
> % command)
>
> That last condition should be "if command" not "if 'command'" and

Oops, you're right.

> using has_key() is probably clearer.

OK. I'm still learning Python. This is my first try at Python programming :-)

>
> Apart from the above I'm happy with your patch.
>

Thanks for the feedback.
Now that I thought about it a bit more, wouldn't it be cleaner to have each 
command implemented in a YumCommand object? Then yum_cli_commands would 
become a dictionary mapping name to a YumCommand object. 
YumCommand would implement
getNames()  multiple names for command aliasing
doChecks(cli)  called from cli.parseArguments() or doCommand()
doCommand(cli) the actual command handler
getUsage() short usage description 

Cheersm

Bastiaan


> Menno
>
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