fix: create separate closure for each host function (#8)

extism_test.go

@@ -293,6 +293,91 @@ func TestHost_memory(t *testing.T) {
 	}
 }
 
+func TestHost_multiple(t *testing.T) {
+	manifest := manifest("host_multiple.wasm")
+
+	config := PluginConfig{
+		ModuleConfig: wazero.NewModuleConfig().WithSysWalltime(),
+		EnableWasi:   true,
+	}
+
+	green_message := HostFunction{
+		Name:      "hostGreenMessage",
+		Namespace: "env",
+		Callback: func(ctx context.Context, plugin *CurrentPlugin, userData interface{}, stack []uint64) {
+			offset := stack[0]
+			input, err := plugin.ReadString(offset)
+
+			if err != nil {
+				fmt.Println("🥵", err.Error())
+				panic(err)
+			}
+
+			message := "🟢:" + string(input)
+			offset, err = plugin.WriteString(message)
+
+			if err != nil {
+				fmt.Println("🥵", err.Error())
+				panic(err)
+			}
+
+			stack[0] = offset
+		},
+		Params:  []api.ValueType{api.ValueTypeI64},
+		Results: []api.ValueType{api.ValueTypeI64},
+	}
+
+	purple_message := HostFunction{
+		Name:      "hostPurpleMessage",
+		Namespace: "env",
+		Callback: func(ctx context.Context, plugin *CurrentPlugin, userData interface{}, stack []uint64) {
+			offset := stack[0]
+			input, err := plugin.ReadString(offset)
+
+			if err != nil {
+				fmt.Println("🥵", err.Error())
+				panic(err)
+			}
+
+			message := "🟣:" + string(input)
+			offset, err = plugin.WriteString(message)
+
+			if err != nil {
+				fmt.Println("🥵", err.Error())
+				panic(err)
+			}
+
+			stack[0] = offset
+		},
+		Params:  []api.ValueType{api.ValueTypeI64},
+		Results: []api.ValueType{api.ValueTypeI64},
+	}
+
+	hostFunctions := []HostFunction{
+		purple_message,
+		green_message,
+	}
+
+	ctx := context.Background()
+	pluginInst, err := NewPlugin(ctx, manifest, config, hostFunctions)
+
+	if err != nil {
+		panic(err)
+	}
+
+	_, res, err := pluginInst.Call(
+		"say_green",
+		[]byte("John Doe"),
+	)
+	assert.Equal(t, "🟢:🫱 Hey from say_green John Doe", string(res))
+
+	_, res, err = pluginInst.Call(
+		"say_purple",
+		[]byte("Jane Doe"),
+	)
+	assert.Equal(t, "🟣:👋 Hello from say_purple Jane Doe", string(res))
+}
+
 func TestHTTP_allowed(t *testing.T) {
 	manifest := manifest("http.wasm")
 	manifest.AllowedHosts = []string{"jsonplaceholder.*.com"}

host.go

@@ -181,14 +181,22 @@ func buildHostModule(ctx context.Context, rt wazero.Runtime, name string, funcs
 
 func defineCustomHostFunctions(builder wazero.HostModuleBuilder, funcs []HostFunction) {
 	for _, f := range funcs {
+
+		// Go closures capture variables by reference, not by value.
+		// This means that if you directly use f inside the closure without creating
+		// a separate variable (closure) and assigning the value of f to it, you might run into unexpected behavior.
+		// All the closures created in the loop would end up referencing the same f, which could lead to incorrect or unintended results.
+		// See: https://github.com/extism/go-sdk/issues/5#issuecomment-1666774486
+		closure := f
+
 		builder.NewFunctionBuilder().WithGoFunction(api.GoFunc(func(ctx context.Context, stack []uint64) {
 			if plugin, ok := ctx.Value("plugin").(*Plugin); ok {
-				f.Callback(ctx, &CurrentPlugin{plugin}, f.UserData, stack)
+				closure.Callback(ctx, &CurrentPlugin{plugin}, closure.UserData, stack)
 				return
 			}
 
 			panic("Invalid context, `plugin` key not found")
-		}), f.Params, f.Results).Export(f.Name)
+		}), closure.Params, closure.Results).Export(closure.Name)
 	}
 }
 

plugins/host_multiple/go.mod

@@ -0,0 +1,8 @@
+module github.com/extism/extism-sdk-plugins-host-multiple
+
+go 1.20
+
+require (
+	github.com/extism/go-pdk v0.0.0-20230119214914-65bffbeb3e64 // indirect
+	github.com/valyala/fastjson v1.6.3 // indirect
+)

plugins/host_multiple/go.sum

@@ -0,0 +1,4 @@
+github.com/extism/go-pdk v0.0.0-20230119214914-65bffbeb3e64 h1:IfR1k741q+yQLvv5sLShCkvt3FgKU4wQVJfp7hhb/iY=
+github.com/extism/go-pdk v0.0.0-20230119214914-65bffbeb3e64/go.mod h1:1wdiAoG8306g4WK+6laBrS+75089/0V4XRVTllt8b5U=
+github.com/valyala/fastjson v1.6.3 h1:tAKFnnwmeMGPbwJ7IwxcTPCNr3uIzoIj3/Fh90ra4xc=
+github.com/valyala/fastjson v1.6.3/go.mod h1:CLCAqky6SMuOcxStkYQvblddUtoRxhYMGLrsQns1aXY=

plugins/host_multiple/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"github.com/extism/go-pdk"
+)
+
+//export hostPurpleMessage
+func hostPurpleMessage(offset uint64) uint64
+
+func purpleMessage(message string) pdk.Memory {
+	messageMemory := pdk.AllocateString(message)
+	off := hostPurpleMessage(messageMemory.Offset())
+	return pdk.FindMemory(off)
+}
+
+//export hostGreenMessage
+func hostGreenMessage(offset uint64) uint64
+
+func greenMessage(message string) pdk.Memory {
+	messageMemory := pdk.AllocateString(message)
+	off := hostGreenMessage(messageMemory.Offset())
+	return pdk.FindMemory(off)
+}
+
+//export say_purple
+func say_purple() int32 {
+	input := pdk.InputString()
+	output := "👋 Hello from say_purple " + input
+
+	mem := purpleMessage(output)
+
+	pdk.OutputMemory(mem)
+	return 0
+
+}
+
+//export say_green
+func say_green() int32 {
+	input := pdk.Input()
+	output := "🫱 Hey from say_green " + string(input)
+
+	mem := greenMessage(output)
+
+	pdk.OutputMemory(mem)
+	return 0
+
+}
+func main() {}