I decided to take a shot at creating the start to a Nushell Plugin library in GoLang. My first plugin to derive length was a filter, and if you look at the main.go, it would be really hard to start with that and try to roll your own plugin. It would be even harder to try and implement a sink plugin, which has more complicated logic that hands your program a temporary file to read from. I also didn’t account for named arguments.

I was able to re-create the same length plugin, and also two new sink plugins (hello and salad) which are all shown below, and can be found as the library vsoch/nu-plugin.

Sink Plugin

For a quick example of how easy a sink plugin can be, take a look at this example script! You should see the repository for details.


package main
 
import (
	"fmt"
	nu "github.com/vsoch/nu-plugin/pkg/plugin"
)

// sink is your function to pass to the plugin to run
func sink(plugin *nu.SinkPlugin, params interface{}) {
	// a map[string]interface{} with keys, values
	namedParams := plugin.Func.GetNamedParams(params)
	message := "Hello"
	for name, value := range namedParams {
		if name == "name" {
			message = message + " " + value.(string)
		}
	}
	fmt.Println(message)
}

func main() {
	name := "hello"
	usage := "A friendly plugin"
	plugin := nu.NewSinkPlugin(name, usage)
	plugin.Config.AddNamedParam("name", "Optional", "String")
	plugin.Run(sink)
}

Filter Plugin

A filter plugin is even easier, here is an example for length.


package main
 
import nu "github.com/vsoch/nu-plugin/pkg/plugin"

// filter is passed to the plugin to run 
func filter(plugin *nu.FilterPlugin, params interface{}) {
	// can also be getIntPrimitive
	value := plugin.Func.GetStringPrimitive(params)
	// Put your logic here! In this case, we want a length
	intLength := len(value)
	// You must also return the tag with your response
	tag := plugin.Func.GetTag(params)
	// This can also be printStringResponse
	plugin.Func.PrintIntResponse(intLength, tag)
}

func main() {
	name := "len"
	usage := "Return the length of a string"
	plugin := nu.NewFilterPlugin(name, usage)
	// Run the filter function
	plugin.Run(filter)
}

I’m hoping that this can get others started with creating plugins in GoLang, specifically for something related to data science. Check out the examples folder for inspiration, and if you make a plugin, please contribute it to the list in the readme!



Suggested Citation:
Sochat, Vanessa. "Nushell Plugin Library for GoLang." @vsoch (blog), 23 Oct 2019, https://vsoch.github.io/2019/nushell-golang-plugin-library/ (accessed 18 Nov 24).