Fix zsh completion initialization

cmd/wut/cmd_init.go

@@ -116,12 +116,15 @@ _wut_completions() {
   fi
 }
 
-complete -F _wut_completions wut
-
 # zsh completion
 if [[ -n ${ZSH_VERSION-} ]]; then
+  if (( ! $+functions[compdef] || ! $+parameters[_comps] )); then
+    autoload -U +X compinit && compinit
+  fi
   autoload -U +X bashcompinit && bashcompinit
-fi`
+fi
+
+complete -F _wut_completions wut`
 	fmt.Println(wrapper)
 }
 

cmd/wut/cmd_init_test.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"io"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestCmdInitLoadsZshBashCompletionBeforeRegisteringCompletion(t *testing.T) {
+	output := captureStdout(t, cmdInit)
+
+	compdefCheck := strings.Index(output, "if (( ! $+functions[compdef] || ! $+parameters[_comps] )); then")
+	compinitSetup := strings.Index(output, "  autoload -U +X compinit && compinit")
+	bashcompinitSetup := strings.Index(output, "autoload -U +X bashcompinit && bashcompinit")
+	registerCompletion := strings.Index(output, "complete -F _wut_completions wut")
+
+	if compdefCheck == -1 {
+		t.Fatal("init output must check whether compdef and _comps are already available")
+	}
+	if compinitSetup == -1 {
+		t.Fatal("init output is missing zsh compinit setup")
+	}
+	if bashcompinitSetup == -1 {
+		t.Fatal("init output is missing zsh bashcompinit setup")
+	}
+	if registerCompletion == -1 {
+		t.Fatal("init output is missing completion registration")
+	}
+	if compdefCheck > compinitSetup {
+		t.Fatal("zsh compdef check must guard compinit setup")
+	}
+	if compinitSetup > bashcompinitSetup {
+		t.Fatal("zsh compinit setup must run before bashcompinit setup")
+	}
+	if bashcompinitSetup > registerCompletion {
+		t.Fatal("zsh bashcompinit setup must run before completion registration")
+	}
+}
+
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+
+	originalStdout := os.Stdout
+	reader, writer, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("create stdout pipe: %v", err)
+	}
+	defer func() {
+		os.Stdout = originalStdout
+	}()
+
+	os.Stdout = writer
+	fn()
+	if err := writer.Close(); err != nil {
+		t.Fatalf("close stdout writer: %v", err)
+	}
+
+	output, err := io.ReadAll(reader)
+	if err != nil {
+		t.Fatalf("read stdout: %v", err)
+	}
+
+	return string(output)
+}