chore: provide usage instruction for CLI argument failures (#12309)

* chore: add usage to # cli arg failures

cli/clibase/cmd.go

@@ -562,6 +562,16 @@ func Chain(ms ...MiddlewareFunc) MiddlewareFunc {
 	return chain(reversed...)
 }
 
+func ShowUsageOnError(next HandlerFunc) HandlerFunc {
+	return func(i *Invocation) error {
+		err := next(i)
+		if err != nil {
+			return xerrors.Errorf("Usage: %s\nError: %w", i.Command.FullUsage(), err)
+		}
+		return nil
+	}
+}
+
 func RequireNArgs(want int) MiddlewareFunc {
 	return RequireRangeArgs(want, want)
 }
@@ -574,7 +584,8 @@ func RequireRangeArgs(start, end int) MiddlewareFunc {
 		panic("start must be >= 0")
 	}
 	return func(next HandlerFunc) HandlerFunc {
-		return func(i *Invocation) error {
+		// ShowUsageOnError will add the command usage before the error message.
+		return ShowUsageOnError(func(i *Invocation) error {
 			got := len(i.Args)
 			switch {
 			case start == end && got != start:
@@ -614,7 +625,7 @@ func RequireRangeArgs(start, end int) MiddlewareFunc {
 			default:
 				return next(i)
 			}
-		}
+		})
 	}
 }
 

cli/errors.go

@@ -45,7 +45,8 @@ func (RootCmd) errorExample() *clibase.Cmd {
 	apiError.(*codersdk.Error).Helper = "Have you tried turning it off and on again?"
 
 	//nolint:errorlint,forcetypeassert
-	apiErrorNoHelper := apiError.(*codersdk.Error)
+	cpy := *apiError.(*codersdk.Error)
+	apiErrorNoHelper := &cpy
 	apiErrorNoHelper.Helper = ""
 
 	// Some flags
@@ -94,7 +95,6 @@ func (RootCmd) errorExample() *clibase.Cmd {
 					)
 				},
 			},
-
 			{
 				Use: "validation",
 				Options: clibase.OptionSet{
@@ -114,6 +114,16 @@ func (RootCmd) errorExample() *clibase.Cmd {
 					return nil
 				},
 			},
+			{
+				Use: "arg-required <required>",
+				Middleware: clibase.Chain(
+					clibase.RequireNArgs(1),
+				),
+				Handler: func(i *clibase.Invocation) error {
+					_, _ = fmt.Fprint(i.Stdout, "Try running this without an argument\n")
+					return nil
+				},
+			},
 		},
 	}