Print help when cmd not found

acmd.go

@@ -210,10 +210,10 @@ func validateSubcommands(cmds []Command) error {
 // Run commands.
 func (r *Runner) Run() error {
 	if r.errInit != nil {
-		return fmt.Errorf("acmd: cannot init runner: %w", r.errInit)
+		return fmt.Errorf("cannot init runner: %w", r.errInit)
 	}
 	if err := r.rootCmd.Do(r.ctx, r.args); err != nil {
-		return fmt.Errorf("acmd: cannot run command: %w", err)
+		return fmt.Errorf("cannot run command: %w", err)
 	}
 	return nil
 }
@@ -233,7 +233,7 @@ func rootDo(cfg Config, cmds []Command) func(ctx context.Context, args []string)
 				// go deeper into subcommands
 				if c.Do == nil {
 					if len(params) == 0 {
-						return errors.New("no args for subcmd provided")
+						return errors.New("no args for command provided")
 					}
 					cmds, args = c.Subcommands, params
 					found = true
@@ -243,16 +243,20 @@ func rootDo(cfg Config, cmds []Command) func(ctx context.Context, args []string)
 			}
 
 			if !found {
-				return errNotFoundAndSuggest(cfg.Output, selected, cmds)
+				return errNotFoundAndSuggest(cfg.Output, cfg.AppName, selected, cmds)
 			}
 		}
 	}
 }
 
-func errNotFoundAndSuggest(w io.Writer, selected string, cmds []Command) error {
-	if suggestion := suggestCommand(selected, cmds); suggestion != "" {
-		fmt.Fprintf(w, "%q is not a subcommand, did you mean %q?\n", selected, suggestion)
+func errNotFoundAndSuggest(w io.Writer, appName, selected string, cmds []Command) error {
+	suggestion := suggestCommand(selected, cmds)
+	if suggestion != "" {
+		fmt.Fprintf(w, "%q unknown command, did you mean %q?\n", selected, suggestion)
+	} else {
+		fmt.Fprintf(w, "%q unknown command\n", selected)
 	}
+	fmt.Fprintf(w, "Run %q for usage.\n\n", appName+" help")
 	return fmt.Errorf("no such command %q", selected)
 }
 

acmd_test.go

@@ -4,13 +4,16 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"io"
 	"os"
 	"sort"
 	"strings"
 	"testing"
 	"time"
 )
 
+var nopUsage = func(cfg Config, cmds []Command) {}
+
 func TestRunner(t *testing.T) {
 	buf := &bytes.Buffer{}
 
@@ -65,13 +68,16 @@ func TestRunner(t *testing.T) {
 
 func TestRunnerMustSetDefaults(t *testing.T) {
 	cmds := []Command{{Name: "foo", Do: nopFunc}}
-	r := RunnerOf(cmds, Config{})
+	r := RunnerOf(cmds, Config{
+		Output: io.Discard,
+		Usage:  nopUsage,
+	})
 
 	err := r.Run()
 	if err == nil {
 		t.Fatal()
 	}
-	if errStr := err.Error(); !strings.Contains(errStr, "acmd: cannot run command: no such command") {
+	if errStr := err.Error(); !strings.Contains(errStr, "cannot run command: no such command") {
 		t.Fatal(err)
 	}
 
@@ -81,9 +87,6 @@ func TestRunnerMustSetDefaults(t *testing.T) {
 	if r.ctx == nil {
 		t.Fatal("context must be set")
 	}
-	if r.cfg.Output != os.Stderr {
-		t.Fatal("incorrect output")
-	}
 	if r.cfg.Usage == nil {
 		t.Fatal("usage nust be set")
 	}
@@ -225,30 +228,32 @@ func TestRunner_suggestCommand(t *testing.T) {
 				{Name: "bar", Do: nopFunc},
 			},
 			args: []string{"fooo"},
-			want: `"fooo" is not a subcommand, did you mean "foo"?` + "\n",
+			want: `"fooo" unknown command, did you mean "foo"?` + "\n" + `Run "ci help" for usage.` + "\n\n",
 		},
 		{
 			cmds: []Command{{Name: "for", Do: nopFunc}},
 			args: []string{"hell"},
-			want: `"hell" is not a subcommand, did you mean "help"?` + "\n",
+			want: `"hell" unknown command, did you mean "help"?` + "\n" + `Run "ci help" for usage.` + "\n\n",
 		},
 		{
 			cmds: []Command{{Name: "for", Do: nopFunc}},
 			args: []string{"verZION"},
-			want: "",
+			want: `"verZION" unknown command` + "\n" + `Run "ci help" for usage.` + "\n\n",
 		},
 		{
 			cmds: []Command{{Name: "for", Do: nopFunc}},
 			args: []string{"verZion"},
-			want: `"verZion" is not a subcommand, did you mean "version"?` + "\n",
+			want: `"verZion" unknown command, did you mean "version"?` + "\n" + `Run "ci help" for usage.` + "\n\n",
 		},
 	}
 
 	for _, tc := range testCases {
 		buf := &bytes.Buffer{}
 		r := RunnerOf(tc.cmds, Config{
-			Args:   tc.args,
-			Output: buf,
+			Args:    tc.args,
+			AppName: "ci",
+			Output:  buf,
+			Usage:   nopUsage,
 		})
 		if err := r.Run(); err != nil && !strings.Contains(err.Error(), "no such command") {
 			t.Fatal(err)

example_test.go

@@ -11,14 +11,17 @@ import (
 	"github.com/cristalhq/acmd"
 )
 
-var nopFunc = func(context.Context, []string) error { return nil }
+var (
+	nopFunc  = func(context.Context, []string) error { return nil }
+	nopUsage = func(cfg acmd.Config, cmds []acmd.Command) {}
+)
 
 func ExampleRunner() {
 	testOut := os.Stdout
 	testArgs := []string{"now", "--times", "3"}
 
 	const format = "15:04:05"
-	now, _ := time.Parse("15:04:05", "10:20:30")
+	now, _ := time.Parse(format, "10:20:30")
 
 	cmds := []acmd.Command{
 		{
@@ -59,6 +62,7 @@ func ExampleRunner() {
 		Version:        "the best v0.x.y",
 		Output:         testOut,
 		Args:           testArgs,
+		Usage:          nopUsage,
 	})
 
 	if err := r.Run(); err != nil {
@@ -136,6 +140,7 @@ func ExampleVersion() {
 		Version:        "the best v0.x.y",
 		Output:         testOut,
 		Args:           testArgs,
+		Usage:          nopUsage,
 	})
 
 	if err := r.Run(); err != nil {
@@ -174,6 +179,7 @@ func ExampleAlias() {
 		Version:        "the best v0.x.y",
 		Output:         testOut,
 		Args:           testArgs,
+		Usage:          nopUsage,
 	})
 
 	if err := r.Run(); err != nil {
@@ -198,13 +204,16 @@ func ExampleAutosuggestion() {
 		Version:        "the best v0.x.y",
 		Output:         testOut,
 		Args:           testArgs,
+		Usage:          nopUsage,
 	})
 
 	if err := r.Run(); err == nil {
 		panic("must fail with command not found")
 	}
 
-	// Output: "baz" is not a subcommand, did you mean "bar"?
+	// Output:
+	// "baz" unknown command, did you mean "bar"?
+	// Run "acmd-example help" for usage.
 }
 
 func ExampleNestedCommands() {