feat: create separate package to make reactor modules easier

.github/workflows/ci.yml

@@ -48,6 +48,7 @@ jobs:
 
           extism call example/tiny_http.wasm --wasi http_get --github-token="$GITHUB_TOKEN" --allow-host "jsonplaceholder.typicode.com" | grep '"userId": 1'
 
+          extism call example/tiny_reactor.wasm read_file --input "example/reactor/test.txt" --allow-path ./example/reactor --wasi --log-level info | grep 'Hello World!'
 
           # run all the tests
           make test

Makefile

@@ -2,13 +2,15 @@
 example:
 	tinygo build -o example/tiny_countvowels.wasm -target wasi ./example/countvowels
 	tinygo build -o example/tiny_http.wasm        -target wasi ./example/http
+	tinygo build -o example/tiny_reactor.wasm     -target wasi ./example/reactor
 
 	GOOS=wasip1 GOARCH=wasm go build -tags std -o example/std_countvowels.wasm ./example/countvowels
 	GOOS=wasip1 GOARCH=wasm go build -tags std -o example/std_http.wasm        ./example/http
 
 test:
 	extism call example/tiny_countvowels.wasm count_vowels --wasi --input "this is a test" --set-config '{"thing": "1234"}'
 	extism call example/tiny_http.wasm        http_get     --wasi --log-level info --allow-host "jsonplaceholder.typicode.com"
+	extism call example/tiny_reactor.wasm read_file --input "example/reactor/test.txt" --allow-path ./example/reactor --wasi --log-level info
 
 	extism call example/std_countvowels.wasm _start     --wasi --input "this is a test" --set-config '{"thing": "1234"}'
 	extism call example/std_http.wasm        _start     --wasi --log-level info --allow-host "jsonplaceholder.typicode.com"

README.md

@@ -326,6 +326,44 @@ python3 app.py
 # => An argument to send to Python!
 ```
 
+## Reactor modules
+
+Since TinyGo doesn't support [Reactor modules](https://dylibso.com/blog/wasi-command-reactor/) yet, If you want to use WASI inside your Reactor module functions (exported functions other than `main`), you'll need to import `wasi-reactor` module which makes sure libc and go runtime are properly initialized:
+
+```go
+package main
+
+import (
+	"os"
+
+	"github.com/extism/go-pdk"
+	_ "github.com/extism/go-pdk/wasi-reactor"
+)
+
+//export read_file
+func read_file() {
+	name := pdk.InputString()
+
+	content, err := os.ReadFile(name)
+	if err != nil {
+		pdk.Log(pdk.LogError, err.Error())
+		return
+	}
+
+	pdk.Output(content)
+}
+
+func main() {}
+```
+
+```bash
+tinygo build -target wasi -o reactor.wasm .\tiny_main.go
+extism call ./reactor.wasm read_file --input "./test.txt" --allow-path . --wasi --log-level info
+# => Hello World!
+```
+
+Note: this is not required if you only have the `main` function.
+
 ### Reach Out!
 
 Have a question or just want to drop in and say hi? [Hop on the Discord](https://extism.org/discord)!

example/reactor/README.md

@@ -0,0 +1,16 @@
+## Reactor module example
+By including this package, you'll turn your plugin into a [Reactor](https://dylibso.com/blog/wasi-command-reactor/) module. This makes sure that you can use WASI (e.g. File Access) in your exported functions.
+
+To test this example, run:
+
+```bash
+tinygo build -target wasi -o reactor.wasm .\tiny_main.go
+extism call ./reactor.wasm read_file --input "./test.txt" --allow-path . --wasi --log-level info
+# => Hello World!
+```
+
+If you don't include the pacakge, you'll see this output:
+```bash
+extism call .\c.wasm read_file --input "./test.txt" --allow-path . --wasi --log-level info
+# => 2024/01/18 20:48:48 open ./test.txt: errno 76
+```

example/reactor/test.txt

@@ -0,0 +1 @@
+Hello World!

example/reactor/tiny_main.go

@@ -0,0 +1,26 @@
+//go:build !std
+// +build !std
+
+package main
+
+import (
+	"os"
+
+	"github.com/extism/go-pdk"
+	_ "github.com/extism/go-pdk/wasi-reactor"
+)
+
+//export read_file
+func read_file() {
+	name := pdk.InputString()
+
+	content, err := os.ReadFile(name)
+	if err != nil {
+		pdk.Log(pdk.LogError, err.Error())
+		return
+	}
+
+	pdk.Output(content)
+}
+
+func main() {}

go.work

@@ -0,0 +1,6 @@
+go 1.21.1
+
+use (
+	.
+	./wasi-reactor
+)

wasi-reactor/extism_pdk_reactor.go

@@ -0,0 +1,9 @@
+package reactor
+
+//export __wasm_call_ctors
+func __wasm_call_ctors()
+
+//export _initialize
+func _initialize() {
+	__wasm_call_ctors()
+}

wasi-reactor/go.mod

@@ -0,0 +1,3 @@
+module github.com/extism/go-pdk/wasi-reactor
+
+go 1.21.1