Add OnInitializeE

cobra.go

@@ -40,6 +40,8 @@ var templateFuncs = template.FuncMap{
 
 var initializers []func()
 
+var initializersE []func() error
+
 // EnablePrefixMatching allows to set automatic prefix matching. Automatic prefix matching can be a dangerous thing
 // to automatically enable in CLI tools.
 // Set this to true to enable it.
@@ -84,6 +86,12 @@ func OnInitialize(y ...func()) {
 	initializers = append(initializers, y...)
 }
 
+// OnInitializeE sets the passed functions to be run when each command's
+// Execute method is called.
+func OnInitializeE(y ...func() error) {
+	initializersE = append(initializersE, y...)
+}
+
 // FIXME Gt is unused by cobra and should be removed in a version 2. It exists only for compatibility with users of cobra.
 
 // Gt takes two types and checks whether the first type is greater than the second. In case of types Arrays, Chans,

cobra_test.go

@@ -1,6 +1,7 @@
 package cobra
 
 import (
+	"errors"
 	"testing"
 	"text/template"
 )
@@ -26,3 +27,30 @@ func TestAddTemplateFunctions(t *testing.T) {
 		t.Errorf("Expected UsageString: %v\nGot: %v", expected, got)
 	}
 }
+
+func Test_OnInitialize(t *testing.T) {
+	call := false
+	c := &Command{Use: "c", Run: emptyRun}
+	OnInitialize(func() {
+		call = true
+	})
+	_, err := executeCommand(c)
+	if err != nil {
+		t.Error(err)
+	}
+	if !call {
+		t.Error("expected OnInitialize func to be called")
+	}
+}
+
+func Test_OnInitializeE(t *testing.T) {
+	c := &Command{Use: "c", Run: emptyRun}
+	e := errors.New("test error")
+	OnInitializeE(func() error {
+		return e
+	})
+	_, err := executeCommand(c)
+	if err != e {
+		t.Error("expected error: %w", e)
+	}
+}

command.go

@@ -830,6 +830,10 @@ func (c *Command) execute(a []string) (err error) {
 		return flag.ErrHelp
 	}
 
+	if err := c.preRunE(); err != nil {
+		return err
+	}
+
 	c.preRun()
 
 	argWoFlags := c.Flags().Args()
@@ -902,6 +906,17 @@ func (c *Command) preRun() {
 	}
 }
 
+func (c *Command) preRunE() error {
+	for _, x := range initializersE {
+		err := x()
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // ExecuteContext is the same as Execute(), but sets the ctx on the command.
 // Retrieve ctx by calling cmd.Context() inside your *Run lifecycle or ValidArgs
 // functions.