issue#798 support initializers that return error

cobra.go

@@ -37,6 +37,7 @@ var templateFuncs = template.FuncMap{
 }
 
 var initializers []func()
+var initializersWithError []func() error
 
 // EnablePrefixMatching allows to set automatic prefix matching. Automatic prefix matching can be a dangerous thing
 // to automatically enable in CLI tools.
@@ -76,6 +77,12 @@ 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) {
+	initializers = append(initializers, 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,

command.go

@@ -727,6 +727,11 @@ func (c *Command) execute(a []string) (err error) {
 
 	c.preRun()
 
+	err = c.preRunE()
+	if err != nil {
+		return err
+	}
+
 	argWoFlags := c.Flags().Args()
 	if c.DisableFlagParsing {
 		argWoFlags = a
@@ -793,6 +798,15 @@ func (c *Command) preRun() {
 	}
 }
 
+func (c *Command) preRunE() {
+	for _, x := range initializersWithError {
+		err := x()
+		if err != nil {
+			return err
+		}
+	}
+}
+
 // Execute uses the args (os.Args[1:] by default)
 // and run through the command tree finding appropriate matches
 // for commands and then corresponding flags.