feat: reuse errors

errors.go

@@ -0,0 +1,11 @@
+package gozero
+
+import "errors"
+
+var (
+	// ErrNoValidEngine is returned when no valid engine is found
+	ErrNoValidEngine = errors.New("no valid engine found")
+
+	// ErrNoEngines is returned when no engines are provided
+	ErrNoEngines = errors.New("no engines provided")
+)

gozero.go

@@ -2,7 +2,6 @@ package gozero
 
 import (
 	"context"
-	"errors"
 	"os/exec"
 
 	"github.com/projectdiscovery/gozero/cmdexec"
@@ -17,7 +16,7 @@ type Gozero struct {
 // New creates a new gozero executor
 func New(options *Options) (*Gozero, error) {
 	if len(options.Engines) == 0 {
-		return nil, errors.New("no engines provided")
+		return nil, ErrNoEngines
 	}
 	// attempt to locate the interpreter by executing it
 	for _, engine := range options.Engines {
@@ -32,7 +31,7 @@ func New(options *Options) (*Gozero, error) {
 		}
 	}
 	if options.engine == "" {
-		return nil, errors.New("no valid engine found")
+		return nil, ErrNoValidEngine
 	}
 	return &Gozero{Options: options}, nil
 }

gozero_test.go

@@ -32,3 +32,27 @@ func TestEval(t *testing.T) {
 	err = input.Cleanup()
 	require.Nil(t, err)
 }
+
+func TestErr(t *testing.T) {
+	opts := &Options{}
+	if osutils.IsWindows() {
+		opts.Engines = []string{"nonexistent.exe"}
+	} else {
+		opts.Engines = []string{"nonexistent"}
+	}
+	gozero, err := New(opts)
+	require.NotNil(t, err)
+	require.Nil(t, gozero)
+	require.ErrorIs(t, err, ErrNoValidEngine)
+
+	opts.Engines = []string{}
+	gozero, err = New(opts)
+	require.NotNil(t, err)
+	require.Nil(t, gozero)
+	require.ErrorIs(t, err, ErrNoEngines)
+
+	opts.Engines = []string{"python3"}
+	gozero, err = New(opts)
+	require.Nil(t, err)
+	require.NotNil(t, gozero)
+}