Include --help and --version flag in completion (#1813)

Fixes #1786

The --help, -h, --version and -v flags are normally added when the
`execute()` function is called on a command.  When doing completion
we don't call `execute()` so we need to add these flags explicitly to
the command being completed.

Also, we disable all further completions if the 'help' or 'version'
flags are present on the command-line.

Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>

command.go

@@ -30,6 +30,8 @@ import (
 	flag "github.com/spf13/pflag"
 )
 
+const FlagSetByCobraAnnotation = "cobra_annotation_flag_set_by_cobra"
+
 // FParseErrWhitelist configures Flag parse errors to be ignored
 type FParseErrWhitelist flag.ParseErrorsWhitelist
 
@@ -1064,6 +1066,7 @@ func (c *Command) InitDefaultHelpFlag() {
 			usage += c.Name()
 		}
 		c.Flags().BoolP("help", "h", false, usage)
+		_ = c.Flags().SetAnnotation("help", FlagSetByCobraAnnotation, []string{"true"})
 	}
 }
 
@@ -1089,6 +1092,7 @@ func (c *Command) InitDefaultVersionFlag() {
 		} else {
 			c.Flags().Bool("version", false, usage)
 		}
+		_ = c.Flags().SetAnnotation("version", FlagSetByCobraAnnotation, []string{"true"})
 	}
 }
 

completions.go

@@ -274,6 +274,12 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	}
 	finalCmd.ctx = c.ctx
 
+	// These flags are normally added when `execute()` is called on `finalCmd`,
+	// however, when doing completion, we don't call `finalCmd.execute()`.
+	// Let's add the --help and --version flag ourselves.
+	finalCmd.InitDefaultHelpFlag()
+	finalCmd.InitDefaultVersionFlag()
+
 	// Check if we are doing flag value completion before parsing the flags.
 	// This is important because if we are completing a flag value, we need to also
 	// remove the flag name argument from the list of finalArgs or else the parsing
@@ -306,6 +312,12 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 		}
 	}
 
+	// Look for the --help or --version flags.  If they are present,
+	// there should be no further completions.
+	if helpOrVersionFlagPresent(finalCmd) {
+		return finalCmd, []string{}, ShellCompDirectiveNoFileComp, nil
+	}
+
 	// We only remove the flags from the arguments if DisableFlagParsing is not set.
 	// This is important for commands which have requested to do their own flag completion.
 	if !finalCmd.DisableFlagParsing {
@@ -477,6 +489,18 @@ func (c *Command) getCompletions(args []string) (*Command, []string, ShellCompDi
 	return finalCmd, completions, directive, nil
 }
 
+func helpOrVersionFlagPresent(cmd *Command) bool {
+	if versionFlag := cmd.Flags().Lookup("version"); versionFlag != nil &&
+		len(versionFlag.Annotations[FlagSetByCobraAnnotation]) > 0 && versionFlag.Changed {
+		return true
+	}
+	if helpFlag := cmd.Flags().Lookup("help"); helpFlag != nil &&
+		len(helpFlag.Annotations[FlagSetByCobraAnnotation]) > 0 && helpFlag.Changed {
+		return true
+	}
+	return false
+}
+
 func getFlagNameCompletions(flag *pflag.Flag, toComplete string) []string {
 	if nonCompletableFlag(flag) {
 		return []string{}