run: preserve the error type from stdlib/flag

command.go

@@ -124,18 +124,19 @@ func (c *Command) run(args []string) error {
 
 		// Parse flags
 		err := c.parseFlags(args)
-		if err != nil {
-			if c.app.errorHandler != nil {
-				return c.app.errorHandler(c.commandPath, err)
-			}
-			return fmt.Errorf("Error: %s\nSee '%s --help' for usage", err, c.commandPath)
-		}
 
 		// Help takes precedence
-		if c.helpFlag {
+		if errors.Is(err, flag.ErrHelp) || c.helpFlag {
 			c.PrintHelp()
 			return nil
 		}
+
+		if err != nil {
+			if c.app.errorHandler != nil {
+				return c.app.errorHandler(c.commandPath, err)
+			}
+			return fmt.Errorf("Error: %w\nSee '%s --help' for usage", err, c.commandPath)
+		}
 	}
 
 	// Do we have an action?

go.mod

@@ -1,3 +1,5 @@
 module github.com/leaanthony/clir
 
 go 1.12
+
+require github.com/rogpeppe/go-internal v1.12.0 // indirect

go.sum

@@ -0,0 +1,28 @@
+github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
+github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/mod v0.9.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f h1:v4INt8xihDGvnrfjMDVXGxw9wrfxYyCjk0KbXjhR55s=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.1.12 h1:VveCTK38A2rkS8ZqFY25HIDFscX5X9OoEhJd3quQmXU=
+golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

script_test.go

@@ -0,0 +1,47 @@
+package clir
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/rogpeppe/go-internal/testscript"
+)
+
+// To understand where testscript comes from and what it does, see:
+// - https://github.com/rogpeppe/go-internal/tree/master?tab=readme-ov-file#testscript
+// - https://bitfieldconsulting.com/golang/test-scripts
+func TestMain(m *testing.M) {
+	os.Exit(testscript.RunMain(m, map[string]func() int{
+		"clir": Main,
+	}))
+}
+
+func TestScript(t *testing.T) {
+	testscript.Run(t, testscript.Params{
+		Dir: "testdata",
+	})
+}
+
+type Flags struct {
+	Bar int `flag:"bar" description:"How many bars"`
+}
+
+func Main() int {
+	cli := NewCli("clir", "a clir executable for testscript", "")
+	flags := &Flags{}
+	cli.NewSubCommand("foo", "Foo the bar").
+		AddFlags(flags).
+		Action(func() error { return foo(flags) })
+
+	if err := cli.Run(); err != nil {
+		fmt.Println("Error:", err)
+		return 1
+	}
+	return 0
+}
+
+func foo(flags *Flags) error {
+	fmt.Println("this is Foo. Flags:", flags)
+	return nil
+}

testdata/help-flags.txt

@@ -0,0 +1,67 @@
+#
+# no flags: print top-level help text
+#
+exec clir
+cmp stdout top-level-help
+! stderr .
+
+#
+# -help flag: print top level help text
+#
+exec clir -help
+cmp stdout top-level-help
+! stderr .
+
+# Introduced by PR #22
+# -h flag: print top level help text
+#
+exec clir -h
+cmp stdout top-level-help
+! stderr .
+
+#
+# known subcommand (foo): execute it
+#
+exec clir foo
+cmp stdout foo-output
+! stderr .
+
+#
+# -help flag to known subcommand (foo): print specific help
+#
+exec clir foo -help
+cmp stdout foo-help
+! stderr .
+
+# Introduced by PR #22
+# -h flag to known subcommand (foo): print specific help
+exec clir foo -h
+cmp stdout foo-help
+! stderr .
+
+
+-- top-level-help --
+clir - a clir executable for testscript
+
+Available commands:
+
+   foo   Foo the bar 
+
+Flags:
+
+  -help
+    	Get help on the 'clir' command.
+
+-- foo-output --
+this is Foo. Flags: &{0}
+-- foo-help --
+clir - a clir executable for testscript
+
+clir foo - Foo the bar
+Flags:
+
+  -bar int
+    	How many bars
+  -help
+    	Get help on the 'clir foo' command.
+