WASI Example

This example shows how to access the local files.

Generate Go code

A proto file is under ./cat.

$ protoc --go-plugin_out=. --go-plugin_opt=paths=source_relative cat/cat.proto

Pass fs.FS in a host

A host can control which files/dirs plugins can access.

import (
    "github.com/knqyf263/go-plugin/options"
)

//go:embed testdata/hello.txt

var f embed.FS

func run() error {
        ctx := context.Background()
		mc := wazero.NewModuleConfig().
            WithStdout(os.Stdout). // Attach stdout so that the plugin can write outputs to stdout
            WithStderr(os.Stderr). // Attach stderr so that the plugin can write errors to stderr
            WithFS(f)              // Loaded plugins can access only files that the host allows.
        p, err := cat.NewFileCatPlugin(ctx, cat.WazeroModuleConfig(mc))

In this example, the host just passes testdata/hello.txt via FileCatPluginOption, but you can pass whatever you want. Please refer to io/fs.

Open a file in a plugin

A plugin can open a file as usual.

b, err := os.ReadFile(request.GetFilePath())
if err != nil {
    return cat.FileCatReply{}, err
}

Compile a plugin

Use TinyGo to compile the plugin to Wasm.

$ tinygo build -o plugin/plugin.wasm -scheduler=none -target=wasi --no-debug plugin/plugin.go

Run

main.go loads the above plugin.

$ go run main.go
File loading...
Hello WASI!