A vlang adaptation of the nushell python example plugin https://github.com/nushell/nushell/blob/main/crates/nu_plugin_python/plugin.py

nu_plugin_vlang.v

import os
import json

struct Signature {
	name                string
	usage               string
	extra_usage         string
	required_positional []string
	optional_positional []string
	named               []string
	search_terms        []string
	is_filter           bool
	creates_scope       bool
	category            string
}

const example_response = '{
        "Value": {
            "List": {
                "vals": [
                    {
                        "Record": {
                            "cols": ["one", "two", "three"],
                            "vals": [
                                {
                                    "Int": {
                                        "val": 8,
                                        "span": {"start": 0, "end": 1}
                                    }
                                },
                                {
                                    "Int": {
                                        "val": 2,
                                        "span": {"start": 0, "end": 1}
                                    }
                                },
                                {
                                    "Int": {
                                        "val": 0,
                                        "span": {"start": 0, "end": 1}
                                    }
                                }
                            ],
                            "span": {"start": 0, "end": 1}
                        }
                    },
					{
                        "Record": {
                            "cols": ["one", "two", "three"],
                            "vals": [
                                {
                                    "Int": {
                                        "val": 0,
                                        "span": {"start": 0, "end": 1}
                                    }
                                },
                                {
                                    "Int": {
                                        "val": 1,
                                        "span": {"start": 0, "end": 1}
                                    }
                                },
                                {
                                    "Int": {
                                        "val": 5,
                                        "span": {"start": 0, "end": 1}
                                    }
                                }
                            ],
                            "span": {"start": 0, "end": 1}
                        }
                    }
				],
				"span": {"start": 0, "end": 1}
			}
		}
	}'

fn main() {
	mut file := os.open_file('output.log', 'a') or { panic(err) }
	defer {
		file.close()
	}

	plugin_call := os.get_line()

	if plugin_call == '"Signature"' {
		s := Signature{
			name: 'vplugin'
			usage: 'Example Nushell plugin for the V programming language'
			extra_usage: ''
			required_positional: []string{}
			optional_positional: []string{}
			named: []string{}
			search_terms: []string{}
			is_filter: false
			creates_scope: false
			category: 'Experimental'
		}

		print('{"Signature": [${json.encode(s)}]}')
	} else if plugin_call.starts_with('{"CallInfo"') {
		print(example_response)
	} else {
		print('{
            "Error": {
                "label": "ERROR from plugin",
                "msg": "error message pointing to call head span",
                "span": {"start": 0, "end": 1},
            }
        }')
	}

	file.write_string('$plugin_call\n') or { panic(err) }
}

v -prod plugin.v
register -e json plugin.exe

vplugin
╭───┬─────┬─────┬───────╮
│ # │ one │ two │ three │
├───┼─────┼─────┼───────┤
│ 0 │   8 │   2 │     0 │
│ 1 │   0 │   1 │     5 │
╰───┴─────┴─────┴───────╯