fix: check module IsClosed before a function call, not after

extism.go

@@ -451,6 +451,10 @@ func (p *Plugin) Call(name string, data []byte) (uint32, []byte, error) {
 
 // Call a function by name with the given input and context, returning the output
 func (p *Plugin) CallWithContext(ctx context.Context, name string, data []byte) (uint32, []byte, error) {
+	if p.mainModule.IsClosed() {
+		return 0, nil, fmt.Errorf("module is closed")
+	}
+
 	ctx = context.WithValue(ctx, PluginCtxKey("extism"), p.extism)
 	if p.Timeout > 0 {
 		var cancel context.CancelFunc
@@ -497,11 +501,6 @@ func (p *Plugin) CallWithContext(ctx context.Context, name string, data []byte)
 		exitCode := exitErr.ExitCode()
 
 		if exitCode == 0 {
-			// It's possible for the function to return 0 as an error code, even
-			// if the module is closed.
-			if p.mainModule.IsClosed() {
-				return 0, nil, fmt.Errorf("module is closed")
-			}
 			err = nil
 		}
 

extism_test.go

@@ -781,6 +781,23 @@ func TestCountVowels(t *testing.T) {
 	}
 }
 
+func TestCountVowelsStdGo(t *testing.T) {
+	manifest := manifest("std_command.wasm")
+
+	if plugin, ok := pluginInstance(t, manifest); ok {
+		defer plugin.Close(context.Background())
+
+		exit, output, err := plugin.Call("_start", []byte("ben"))
+
+		result := string(output)
+		if assertCall(t, err, exit) {
+			expected := "hello ben"
+
+			assert.Equal(t, expected, result)
+		}
+	}
+}
+
 func TestMultipleCallsOutput(t *testing.T) {
 	manifest := manifest("count_vowels.wasm")
 

plugins/std_command/build.sh

@@ -0,0 +1,2 @@
+# standard go compiler, command module
+GOOS=wasip1 GOARCH=wasm go build -tags std -o ../../wasm/std_command.wasm .

plugins/std_command/go.mod

@@ -0,0 +1,5 @@
+module github.com/extism/extism-sdk-plugins-count-vowels
+
+go 1.23.6
+
+require github.com/extism/go-pdk v1.1.1

plugins/std_command/go.sum

@@ -0,0 +1,2 @@
+github.com/extism/go-pdk v1.1.1 h1:c8twD4RXAgh5Q3bgQ4srBLnVJ1OJK1ZlKhD/0P/pbxA=
+github.com/extism/go-pdk v1.1.1/go.mod h1:Gz+LIU/YCKnKXhgge8yo5Yu1F/lbv7KtKFkiCSzW/P4=

plugins/std_command/main.go

@@ -0,0 +1,14 @@
+//go:build std
+// +build std
+
+package main
+
+import (
+	"github.com/extism/go-pdk"
+)
+
+func main() {
+	input := pdk.InputString()
+
+	pdk.OutputString("hello " + input)
+}