view docs/api/02_components/01_commands.md @ 1051:971b4d67e82a

serve: Fix problems with assets disappearing between servings. When an asset file changes, its source's pipeline is re-run. But that created a bake record that only had that pipeline's output, so the other outputs were incorrectly considered empty and therefore any stray files were removed. Now we copy over bake records for the pipelines we don't run.
author Ludovic Chabant <ludovic@chabant.com>
date Fri, 26 Jan 2018 18:05:02 -0800
parents dce482f7c62d
children
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---
title: Chef Commands
---

To provide new `chef` commands, you need to override the `getCommands` method of
your plugin, and return command instances:


```python
class MyPlugin(PieCrustPlugin):
    name = 'myplugin'

    def getCommands(self):
        return [
                MyNewCommand()]
```


To create a command class, inherit from the `ChefCommand` base class:

```python
from piecrust.commands.base import ChefCommand

class MyNewCommand(ChefCommand):
    def __init__(self):
        super(MyNewCommand, self).__init__()
        self.name = 'foobar'
        self.description = "Does some foobar thing."

    def setupParser(self, parser, app):
        parser.add_argument('thing')

    def run(self, ctx):
        print("Doing %s" % ctx.args.thing)
```


* The `name` will be used for command line invocation, _i.e._ your new command
  will be invoked with `chef foobar`.
* The `description` will be used for help pages like `chef --help`.
* The `setupParser` method passes an `argparse.ArgumentParser` and a `PieCrust`
  application. You're supposed to setup the syntax for your commend there.
* The `run` method is called when your command is executed. The `ctx` object
  contains a couple useful things, among others:
    * `args` is the namespace obtained from running `parse_args`. It has all the
      values of the arguments for your command.
    * `app` is the instance of the current `PieCrust` application.
    * For the other things, check-out `piecrust.commands.base.CommandContext`.