Add suggestions support (#977)

.github/workflows/cli.yml

@@ -37,7 +37,7 @@ jobs:
       - name: vet
         run: go run internal/build/build.go vet
 
-      - name: test with tags
+      - name: test with urfave_cli_no_docs tag
         run: go run internal/build/build.go -tags urfave_cli_no_docs test
 
       - name: test
@@ -47,7 +47,7 @@ jobs:
         run: go run internal/build/build.go check-binary-size
 
       - name: check-binary-size with tags (informational only)
-        run: go run internal/build/build.go -tags urfave_cli_no_docs check-binary-size || true
+        run: go run internal/build/build.go -tags urfave_cli_no_docs check-binary-size
 
       - name: Upload coverage to Codecov
         if: success() && matrix.go == '1.18.x' && matrix.os == 'ubuntu-latest'

README.md

@@ -63,7 +63,7 @@ You can use the following build tags:
 
 When set, this removes `ToMarkdown` and `ToMan` methods, so your application
 won't be able to call those. This reduces the resulting binary size by about
-300-400 KB (measured using Go 1.18.1 on Linux/amd64), due to less dependencies.
+300-400 KB (measured using Go 1.18.1 on Linux/amd64), due to fewer dependencies.
 
 ### GOPATH
 

app.go

@@ -94,6 +94,8 @@ type App struct {
 	// single-character bool arguments into one
 	// i.e. foobar -o -v -> foobar -ov
 	UseShortOptionHandling bool
+	// Enable suggestions for commands and flags
+	Suggest bool
 
 	didSetup bool
 }
@@ -264,6 +266,11 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 			return err
 		}
 		_, _ = fmt.Fprintf(a.Writer, "%s %s\n\n", "Incorrect Usage.", err.Error())
+		if a.Suggest {
+			if suggestion, err := a.suggestFlagFromError(err, ""); err == nil {
+				fmt.Fprintf(a.Writer, suggestion)
+			}
+		}
 		_ = ShowAppHelp(cCtx)
 		return err
 	}
@@ -383,6 +390,11 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 			return err
 		}
 		_, _ = fmt.Fprintf(a.Writer, "%s %s\n\n", "Incorrect Usage.", err.Error())
+		if a.Suggest {
+			if suggestion, err := a.suggestFlagFromError(err, cCtx.Command.Name); err == nil {
+				fmt.Fprintf(a.Writer, suggestion)
+			}
+		}
 		_ = ShowSubcommandHelp(cCtx)
 		return err
 	}

command.go

@@ -119,6 +119,11 @@ func (c *Command) Run(ctx *Context) (err error) {
 		}
 		_, _ = fmt.Fprintln(cCtx.App.Writer, "Incorrect Usage:", err.Error())
 		_, _ = fmt.Fprintln(cCtx.App.Writer)
+		if ctx.App.Suggest {
+			if suggestion, err := ctx.App.suggestFlagFromError(err, c.Name); err == nil {
+				fmt.Fprintf(cCtx.App.Writer, suggestion)
+			}
+		}
 		_ = ShowCommandHelp(cCtx, c.Name)
 		return err
 	}
@@ -249,6 +254,7 @@ func (c *Command) startApp(ctx *Context) error {
 	app.ErrWriter = ctx.App.ErrWriter
 	app.ExitErrHandler = ctx.App.ExitErrHandler
 	app.UseShortOptionHandling = ctx.App.UseShortOptionHandling
+	app.Suggest = ctx.App.Suggest
 
 	app.categories = newCommandCategories()
 	for _, command := range c.Subcommands {

docs/v2/manual.md

@@ -1410,6 +1410,13 @@ In this example the flag could be used like this :
 
 Side note: quotes may be necessary around the date depending on your layout (if you have spaces for instance)
 
+### Suggestions
+
+To enable flag and command suggestions, set `app.Suggest = true`. If the suggest
+feature is enabled, then the help output of the corresponding command will
+provide an appropriate suggestion for the provided flag or subcommand if
+available.
+
 ### Full API Example
 
 **Notice**: This is a contrived (functioning) example meant strictly for API

go.mod

@@ -4,6 +4,7 @@ go 1.18
 
 require (
 	github.com/BurntSushi/toml v1.1.0
+	github.com/antzucaro/matchr v0.0.0-20210222213004-b04723ef80f0
 	github.com/cpuguy83/go-md2man/v2 v2.0.1
 	golang.org/x/text v0.3.7
 	gopkg.in/yaml.v2 v2.4.0

go.sum

@@ -1,9 +1,17 @@
 github.com/BurntSushi/toml v1.1.0 h1:ksErzDEI1khOiGPgpwuI7x2ebx/uXQNw7xJpn9Eq1+I=
 github.com/BurntSushi/toml v1.1.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/antzucaro/matchr v0.0.0-20180616170659-cbc221335f3c h1:CucViv7orgFBMkehuFFdkCVF5ERovbkRRyhvaYaHu/k=
+github.com/antzucaro/matchr v0.0.0-20180616170659-cbc221335f3c/go.mod h1:bV/CkX4+ANGDaBwbHkt9kK287al/i9BsB18PRBvyqYo=
+github.com/antzucaro/matchr v0.0.0-20210222213004-b04723ef80f0 h1:R/qAiUxFT3mNgQaNqJe0IVznjKRNm23ohAIh9lgtlzc=
+github.com/antzucaro/matchr v0.0.0-20210222213004-b04723ef80f0/go.mod h1:v3ZDlfVAL1OrkKHbGSFFK60k0/7hruHPDq2XMs9Gu6U=
 github.com/cpuguy83/go-md2man/v2 v2.0.1 h1:r/myEWzV9lfsM1tFLgDyu0atFtJ1fXn261LKYj/3DxU=
 github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/shurcooL/sanitized_anchor_name v1.0.0 h1:PdmoCO6wvbs+7yrJyMORt4/BmY5IYyJwS/kOiWx8mHo=
+github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e h1:FDhOuMEY4JVRztM/gsbk+IKUQ8kj74bxZrgw87eMMVc=

godoc-current.txt

@@ -305,6 +305,8 @@ type App struct {
 	// single-character bool arguments into one
 	// i.e. foobar -o -v -> foobar -ov
 	UseShortOptionHandling bool
+	// Enable suggestions for commands and flags
+	Suggest bool
 
 	// Has unexported fields.
 }

help.go

@@ -10,9 +10,14 @@ import (
 	"unicode/utf8"
 )
 
+const (
+	helpName  = "help"
+	helpAlias = "h"
+)
+
 var helpCommand = &Command{
-	Name:      "help",
-	Aliases:   []string{"h"},
+	Name:      helpName,
+	Aliases:   []string{helpAlias},
 	Usage:     "Shows a list of commands or help for one command",
 	ArgsUsage: "[command]",
 	Action: func(cCtx *Context) error {
@@ -27,8 +32,8 @@ var helpCommand = &Command{
 }
 
 var helpSubcommand = &Command{
-	Name:      "help",
-	Aliases:   []string{"h"},
+	Name:      helpName,
+	Aliases:   []string{helpAlias},
 	Usage:     "Shows a list of commands or help for one command",
 	ArgsUsage: "[command]",
 	Action: func(cCtx *Context) error {
@@ -214,7 +219,13 @@ func ShowCommandHelp(ctx *Context, command string) error {
 	}
 
 	if ctx.App.CommandNotFound == nil {
-		return Exit(fmt.Sprintf("No help topic for '%v'", command), 3)
+		errMsg := fmt.Sprintf("No help topic for '%v'", command)
+		if ctx.App.Suggest {
+			if suggestion := suggestCommand(ctx.App.Commands, command); suggestion != "" {
+				errMsg += ". " + suggestion
+			}
+		}
+		return Exit(errMsg, 3)
 	}
 
 	ctx.App.CommandNotFound(ctx, command)

parse.go

@@ -26,9 +26,8 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 			return err
 		}
 
-		errStr := err.Error()
-		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: -")
-		if errStr == trimmed {
+		trimmed, trimErr := flagFromError(err)
+		if trimErr != nil {
 			return err
 		}
 
@@ -67,6 +66,19 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string, shellComple
 	}
 }
 
+const providedButNotDefinedErrMsg = "flag provided but not defined: -"
+
+// flagFromError tries to parse a provided flag from an error message. If the
+// parsing fials, it returns the input error and an empty string
+func flagFromError(err error) (string, error) {
+	errStr := err.Error()
+	trimmed := strings.TrimPrefix(errStr, providedButNotDefinedErrMsg)
+	if errStr == trimmed {
+		return "", err
+	}
+	return trimmed, nil
+}
+
 func splitShortOptions(set *flag.FlagSet, arg string) []string {
 	shortFlagsExist := func(s string) bool {
 		for _, c := range s[1:] {

suggestions.go

@@ -0,0 +1,75 @@
+package cli
+
+import (
+	"fmt"
+
+	"github.com/antzucaro/matchr"
+)
+
+const didYouMeanTemplate = "Did you mean '%s'?"
+
+func (a *App) suggestFlagFromError(err error, command string) (string, error) {
+	flag, parseErr := flagFromError(err)
+	if parseErr != nil {
+		return "", err
+	}
+
+	flags := a.Flags
+	if command != "" {
+		cmd := a.Command(command)
+		if cmd == nil {
+			return "", err
+		}
+		flags = cmd.Flags
+	}
+
+	suggestion := a.suggestFlag(flags, flag)
+	if len(suggestion) == 0 {
+		return "", err
+	}
+
+	return fmt.Sprintf(didYouMeanTemplate+"\n\n", suggestion), nil
+}
+
+func (a *App) suggestFlag(flags []Flag, provided string) (suggestion string) {
+	distance := 0.0
+
+	for _, flag := range flags {
+		flagNames := flag.Names()
+		if !a.HideHelp {
+			flagNames = append(flagNames, HelpFlag.Names()...)
+		}
+		for _, name := range flagNames {
+			newDistance := matchr.JaroWinkler(name, provided, true)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	if len(suggestion) == 1 {
+		suggestion = "-" + suggestion
+	} else if len(suggestion) > 1 {
+		suggestion = "--" + suggestion
+	}
+
+	return suggestion
+}
+
+// suggestCommand takes a list of commands and a provided string to suggest a
+// command name
+func suggestCommand(commands []*Command, provided string) (suggestion string) {
+	distance := 0.0
+	for _, command := range commands {
+		for _, name := range append(command.Names(), helpName, helpAlias) {
+			newDistance := matchr.JaroWinkler(name, provided, true)
+			if newDistance > distance {
+				distance = newDistance
+				suggestion = name
+			}
+		}
+	}
+
+	return fmt.Sprintf(didYouMeanTemplate, suggestion)
+}