Show suggestions for options based on levenshtein distance

tools/cli/command.go

@@ -301,6 +301,28 @@ func (self *Command) GetVisibleOptions() ([]string, map[string][]*Option) {
 	return group_titles, gmap
 }
 
+func (self *Command) SuggestionsForOption(name_with_hyphens string, max_distance int /* good default is 2 */) []string {
+	ans := make([]string, 0, 8)
+	q := strings.ToLower(name_with_hyphens)
+	self.VisitAllOptions(func(opt *Option) error {
+		for _, a := range opt.Aliases {
+			as := a.String()
+			if utils.LevenshteinDistance(as, q, true) <= max_distance {
+				ans = append(ans, as)
+			}
+		}
+		return nil
+	})
+	utils.StableSort(ans, func(a, b string) bool {
+		la, lb := utils.LevenshteinDistance(a, q, true), utils.LevenshteinDistance(b, q, true)
+		if la != lb {
+			return la < lb
+		}
+		return a < b
+	})
+	return ans
+}
+
 func (self *Command) FindSubCommand(name string) *Command {
 	for _, g := range self.SubCommandGroups {
 		c := g.FindSubCommand(name)

tools/cli/parse-args.go

@@ -26,6 +26,10 @@ func (self *Command) parse_args(ctx *Context, args []string) error {
 			opt = possible_options[0]
 			opt_str = opt.MatchingAlias(NormalizeOptionName(opt_str), !strings.HasPrefix(opt_str, "--"))
 		} else if len(possible_options) == 0 {
+			possibles := self.SuggestionsForOption(opt_str, 2)
+			if len(possibles) > 0 {
+				return &ParseError{Message: fmt.Sprintf("Unknown option: :yellow:`%s`. Did you mean:\n\t%s", opt_str, strings.Join(possibles, "\n\t"))}
+			}
 			return &ParseError{Message: fmt.Sprintf("Unknown option: :yellow:`%s`", opt_str)}
 		} else {
 			ambi := make([]string, len(possible_options))

tools/utils/levenshtein.go

@@ -0,0 +1,46 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+var _ = fmt.Print
+
+// compares two strings and returns the Levenshtein distance between them.
+func LevenshteinDistance(s, t string, ignore_case bool) int {
+	if ignore_case {
+		s = strings.ToLower(s)
+		t = strings.ToLower(t)
+	}
+	d := make([][]int, len(s)+1)
+	for i := range d {
+		d[i] = make([]int, len(t)+1)
+	}
+	for i := range d {
+		d[i][0] = i
+	}
+	for j := range d[0] {
+		d[0][j] = j
+	}
+	for j := 1; j <= len(t); j++ {
+		for i := 1; i <= len(s); i++ {
+			if s[i-1] == t[j-1] {
+				d[i][j] = d[i-1][j-1]
+			} else {
+				min := d[i-1][j]
+				if d[i][j-1] < min {
+					min = d[i][j-1]
+				}
+				if d[i-1][j-1] < min {
+					min = d[i-1][j-1]
+				}
+				d[i][j] = min + 1
+			}
+		}
+
+	}
+	return d[len(s)][len(t)]
+}