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https://github.com/vsoch/nushell-plugin-python

Python module for easy creation of nushell plugins
https://github.com/vsoch/nushell-plugin-python

nu nu-plugin nushell nushell-plugin

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Python module for easy creation of nushell plugins

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# Nushell Plugin Python



[![PyPI version](https://badge.fury.io/py/nushell.svg)](https://pypi.org/project/nushell/)



This is a python module to allow for easy creation of plugins. It's

already fairly easy, but this can improve upon that! Each of the examples provided comes with:



 - the full example in a python file (without the .py extension)

 - containers with nushell to run with regular Python or (for some) a standalone binary (via pyinstaller)

 - README.md files to walk through the usage



Quick start examples for a filter and sink plugin are included below, and you

should see the [examples](examples) folder for the complete code, makefiles, and Dockerfiles.

Please contribute new examples along with tweaks to the code! I developed this in

under a day, so we can likely make it much better, and will need to as nushell

is developed.



## Install



You can install from pip



```bash

$ pip install nushell

```



or from source here:



```bash

$ git clone https://github.com/vsoch/nushell-plugin-python

cd nushell-plugin-python

python setup.py install

```



## Plugin Class Arguments



The following are shared parameters for both filter and sink plugins.



| Name | Description | Required or Default |

|------|-------------|-------------------|

| name | the name of the plugin | required |

| usage | plugin usage | required | 

| logging | enable logging to `nu_plugin_.log` | defaults to True (enabled) |

| add_help | add the `--help` flag | defaults to True |

| parse_params | extract parameters from items | defaults to True |



## Parameters



Parameters can be named or positional arguments that are defined for your

plugin. You can actually have positional and named arguments with the

same name, and define the help string for one (and it will be used by

the other).



### Named Parameters



For either a sink or a filter, you can pass in named arguments, meaning that your

plugin will parse them like:



```

$  -- 

```



or for a boolean (called a Switch)



```

$  --

```



Here are examples of adding all kinds of named arguments



```python

# add_named_argument(name, argType, syntaxShape=None, usage=None)

plugin.add_named_argument("catch", "Switch", usage="catch a random pokemon")

plugin.add_named_argument("list", "Switch", usage="list pokemon names")

plugin.add_named_argument("list-sorted", "Switch", usage="list sorted names")

plugin.add_named_argument("avatar", "Optional", "String", "generate avatar")

plugin.add_named_argument("pokemon", "Optional", "String", "get pokemon")

```



For an argument to be Mandatory, just change "Optional" to "Mandatory" (the 

above plugin doesn't require anything).



### Positional Arguments



Positional arguments come after the plugin name, but don't have a flag.

For example:



```bash

$  

```



Here are examples of adding positional arguments. Each needs a name,

if it's Mandatory or Optional (there is no Switch), the SyntaxShape (e.g. String, Int, Any)

and then a usage string.



```python

# add_positional_argument(name, argType, syntaxShape=None, usage=None)

plugin.add_positional_argument("number", "Mandatory", "Int", usage="number to parse")

plugin.add_positional_argument("secondNumber", "Optional", "Any", usage="second number to parse")

```



## Filter Plugin



A basic filter plugin will instantiate the `FilterPlugin` class, and then

provide a function to run for the filter.



```python

#!/usr/bin/env python3



from nushell.filter import FilterPlugin



# Your filter function will be called by the FilterPlugin, and should

# accept the plugin and the dictionary of params

def runFilter(plugin, params):

    '''runFilter will be executed by the calling SinkPlugin when method is "sink"

    '''

    # Get the string primitive passed by the user

    value = plugin.get_string_primitive()



    # Calculate the length

    intLength = len(value)



    # Print an integer response (can also be print_string_response)

    plugin.print_int_response(intLength)



# The main function is where you create your plugin and run it.

def main():



    # Initialize a new plugin

    plugin = FilterPlugin(name="len", 

                          usage="Return the length of a string")



    # Run the plugin by passing your filter function

    plugin.run(runFilter)



if __name__ == '__main__':

    main()

```



Notably, your filter function should taken a plugin and parsed command line

parameters (dictionary) as arguments. You can use the plugin to perform

several needed functions to send responses back to nushell, or log to `/tmp/nushell-plugin-.log`:



```python

plugin.logger.

plugin.get_string_primitive()

plugin.get_int_primitive()

plugin.print_int_response()

plugin.print_string_response()

```



### Examples



 - [len](examples/len) is a basic function to return the length of a string

 - [plus](examples/plus) adds two ints, and is an example with positional arguments



## Sink Plugin



A sink plugin will instantiate the `SinkPlugin` class, and then hand off

stdin (via a temporary file) to a sink function that you write.

Here is a dummy example.



```python

#!/usr/bin/env python3



from nushell.sink import SinkPlugin



# Your sink function will be called by the sink Plugin, and should

# accept the plugin and the dictionary of params

def sink(plugin, params):

    '''sink will be executed by the calling SinkPlugin when method is "sink"

    '''

    message = "Hello"

    excited = params.get("excited", False)

    name = params.get("name", "")

    

    # If we have a name, add to message

    message = "%s %s" %(message, name)

    

    # Are we excited?

    if excited:

        message += "!"



    print(message)



# The main function is where you create your plugin and run it.

def main():



    # Initialize a new plugin

    plugin = SinkPlugin(name="hello", 

                        usage="A friendly plugin")



    # Add named arguments (notice we check for in params in sink function)

    # add_named_argument(name, argType, syntaxShape=None, usage=None)

    plugin.add_named_argument("excited", "Switch", usage="add an exclamation point!")

    plugin.add_named_argument("name", "Optional", "String", usage="say hello to...")



    # Run the plugin by passing your sink function

    plugin.run(sink)



if __name__ == '__main__':

    main()

```



### Parameters



Since you can pipe content into a sink, the piped content is parsed into a list

and passed with params as the `_pipe` key. For example, if we do:



```bash

> ls | get name | hello --name Dinosaur

Hello Dinosaur

```



And then look in the output file, we see that the parsed params include a pipe

of all the named of the listed files (that we generated above)



```bash

PARAMS {'name': 'Dinosaur', '_pipe': ['Makefile', 'README.md', 'Dockerfile', 'nu_plugin_hello', 'Dockerfile.standalone']}

```



If you don't want to parse the pipe, set your plugin.parse_pipe to False:



```python

plugin.parse_pipe = False

plugin.run(sink)

```



And the result will include the full list of entries with items and tags.



```python

PARAMS {'name': 'Dinosaur', '_pipe': [[{'tag': {'anchor': None, 'span': {'start': 0, 'end': 2}}, 'item': {'Primitive': {'String': 'Makefile'}}}, {'tag': {'anchor': None, 'span': {'start': 0, 'end': 2}}, 'item': {'Primitive': {'String': 'README.md'}}}, {'tag': {'anchor': None, 'span': {'start': 0, 'end': 2}}, 'item': {'Primitive': {'String': 'Dockerfile'}}}, {'tag': {'anchor': None, 'span': {'start': 0, 'end': 2}}, 'item': {'Primitive': {'String': 'nu_plugin_hello'}}}, {'tag': {'anchor': None, 'span': {'start': 0, 'end': 2}}, 'item': {'Primitive': {'String': 'Dockerfile.standalone'}}}]]}

```



### Examples



 - [pokemon](examples/pokemon) ascii pokemon on demand!

 - [hello](examples/hello) say hello using a sink!



## Single Binary



In that you are able to compile your module with [pyinstaller](https://pyinstaller.readthedocs.io/en/stable/operating-mode.html) (e.g., see [examples/len](examples/len)) you can build your python script as a simple binary, and one that doesn't even need nushell installed as a module anymore. Why might you want to do this? It will mean that your plugin is a single file (binary) and you don't need to rely on modules elsewhere in the system. I suspect there are other ways to compile

python into a single binary (e.g., cython) but this was the first I tried, and fairly straight forward.

If you find a different or better way, please contribute to this code base!



**Important** I've found that modules with added data files don't do well (an example is [pokemon](examples/pokemon) here!)

and that's why we can't uninstall pokemon or nushell. However, I think you would have luck with most text based,

simple modules. And of course, you don't have to do this! It's totally ok to keep your Python modules

installed alongside nushell, and used when your plugin is executed.



## License



This code is licensed under the MPL 2.0 [LICENSE](LICENSE).



## Help and Contribution



Please contribute to the package, or post feedback and questions as issues.