Skip exit code 1 for 'help' output (#689)

* skip help error output

* rename error type

cmd/fastly/main.go

@@ -2,6 +2,7 @@
 package main
 
 import (
+	"errors"
 	"io"
 	"log"
 	"net/http"
@@ -142,12 +143,20 @@ func main() {
 	}
 
 	if err != nil {
-		fsterr.Deduce(err).Print(color.Error)
-
 		// NOTE: os.Exit doesn't honour any deferred calls so we have to manually
 		// flush the Sentry buffer here (as well as the deferred call at the top of
 		// the main function).
 		sentry.Flush(sentryTimeout)
+
+		fsterr.Deduce(err).Print(color.Error)
+
+		exitError := fsterr.SkipExitError{}
+		if errors.As(err, &exitError) {
+			if exitError.Skip {
+				return // skip returning an error for 'help' output
+			}
+		}
+
 		os.Exit(1)
 	}
 }

pkg/app/usage.go

@@ -247,7 +247,10 @@ func processCommandInput(
 	var vars map[string]any
 
 	if cmd.IsHelpFlagOnly(opts.Args) && len(opts.Args) == 1 {
-		return command, cmdName, help(vars, nil)
+		return command, cmdName, fsterr.SkipExitError{
+			Skip: true,
+			Err:  help(vars, nil),
+		}
 	}
 
 	// NOTE: We call two similar methods below: ParseContext() and Parse().
@@ -299,7 +302,10 @@ func processCommandInput(
 	}
 
 	if cmd.ContextHasHelpFlag(ctx) && !cmd.IsHelpFlagOnly(opts.Args) {
-		return command, cmdName, help(vars, nil)
+		return command, cmdName, fsterr.SkipExitError{
+			Skip: true,
+			Err:  help(vars, nil),
+		}
 	}
 
 	// NOTE: app.Parse() resets the default values for app.Writers() from
@@ -348,7 +354,7 @@ func processCommandInput(
 	if cmdName == "help" {
 		var buf bytes.Buffer
 		app.Writers(&buf, io.Discard)
-		app.Parse(opts.Args)
+		_, _ = app.Parse(opts.Args)
 		app.Writers(opts.Stdout, io.Discard)
 
 		// The full-fat output of `fastly help` should have a hint at the bottom
@@ -362,13 +368,21 @@ func processCommandInput(
 			fmt.Fprintln(&buf, "")
 		}
 
-		return command, cmdName, fsterr.RemediationError{Prefix: buf.String()}
+		return command, cmdName, fsterr.SkipExitError{
+			Skip: true,
+			Err: fsterr.RemediationError{
+				Prefix: buf.String(),
+			},
+		}
 	}
 
 	// Catch scenario where user wants to view help with the following format:
 	// fastly --help <command>
 	if cmd.IsHelpFlagOnly(opts.Args) {
-		return command, cmdName, help(vars, nil)
+		return command, cmdName, fsterr.SkipExitError{
+			Skip: true,
+			Err:  help(vars, nil),
+		}
 	}
 
 	return command, cmdName, nil

pkg/commands/compute/build_test.go

@@ -567,7 +567,7 @@ func TestBuildGo(t *testing.T) {
 			// NOTE: The following constraints should be kept in-sync with
 			// ./pkg/config/config.toml
 			opts.ConfigFile.Language.Go.TinyGoConstraint = ">= 0.24.0-0" // NOTE: -0 is to allow prereleases.
-			opts.ConfigFile.Language.Go.ToolchainConstraint = ">= 1.17 < 1.19"
+			opts.ConfigFile.Language.Go.ToolchainConstraint = ">= 1.17"
 
 			err = app.Run(opts)
 

pkg/errors/exit_error.go

@@ -0,0 +1,36 @@
+package errors
+
+import (
+	"io"
+
+	"github.com/fastly/cli/pkg/text"
+)
+
+// SkipExitError is an error that can cause the os.Exit(1) to be skipped.
+// An example is 'help' output (e.g. --help).
+type SkipExitError struct {
+	Skip bool
+	Err  error
+}
+
+// Unwrap returns the inner error.
+func (ee SkipExitError) Unwrap() error {
+	return ee.Err
+}
+
+// Error prints the inner error string.
+func (ee SkipExitError) Error() string {
+	if ee.Err == nil {
+		return ""
+	}
+	return ee.Err.Error()
+}
+
+// Print the error to the io.Writer for human consumption.
+// The inner error is always printed via text.Output with an "Error: " prefix
+// and a "." suffix.
+func (ee SkipExitError) Print(w io.Writer) {
+	if ee.Err != nil {
+		text.Error(w, "%s.", ee.Err.Error())
+	}
+}