Add MinLen validator

Author: dopey

ui/options.go

@@ -138,11 +138,17 @@ func WithValidateFunc(fn func(string) error) Option {
 }
 
 // WithValidateNotEmpty adds a custom validation function to a prompt that
-// checks that the propted string is not empty.
+// checks that the prompted string is not empty.
 func WithValidateNotEmpty() Option {
 	return WithValidateFunc(NotEmpty())
 }
 
+// WithValidateMinLen adds a custom validation function to a prompt that
+// checks the input string meets the minimum length requirement.
+func WithValidateMinLen(length int) Option {
+	return WithValidateFunc(MinLen(length))
+}
+
 // WithValidateYesNo adds a custom validation function to a prompt for a Yes/No
 // prompt.
 func WithValidateYesNo() Option {

ui/validators.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"regexp"
 	"strings"
 
 	"github.com/manifoldco/promptui"
@@ -73,3 +74,19 @@ func YesNo() promptui.ValidateFunc {
 		}
 	}
 }
+
+// MinLen is a validation function that checks for a minimum length.
+// An input length <= 0 indicates that the check should not be performed.
+func MinLen(length int) promptui.ValidateFunc {
+	return func(s string) error {
+		if length <= 0 {
+			return nil
+		}
+		re := regexp.MustCompile(`\s+`)
+		next := re.ReplaceAllString(s, "")
+		if len(next) < length {
+			return fmt.Errorf("input does not meet minimum length requirement; must be at least %v characters", length)
+		}
+		return nil
+	}
+}

ui/validators_test.go

@@ -90,3 +90,63 @@ func TestDNS(t *testing.T) {
 		})
 	}
 }
+
+func TestMinLen(t *testing.T) {
+	tests := []struct {
+		name    string
+		length  int
+		input   string
+		wantErr bool
+	}{
+		{
+			name:    "negative",
+			length:  -5,
+			input:   "foobar",
+			wantErr: false,
+		},
+		{
+			name:    "zero",
+			length:  0,
+			input:   "localhost",
+			wantErr: false,
+		},
+		{
+			name:    "greater-than-min-length",
+			length:  5,
+			input:   "foobar",
+			wantErr: false,
+		},
+		{
+			name:    "equal-min-length",
+			length:  6,
+			input:   "foobar",
+			wantErr: false,
+		},
+		{
+			name:    "less-than-min-length",
+			length:  8,
+			input:   "foobar",
+			wantErr: true,
+		},
+		{
+			name:    "ignore-whitespace-characters",
+			length:  15,
+			input:   "  p \t\n#$%@#$ a s s  ",
+			wantErr: true,
+		},
+		{
+			name:    "ignore-whitespace-characters-ok",
+			length:  10,
+			input:   "  p \t\n#$%@#$ a s s  ",
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotErr := MinLen(tt.length)(tt.input) != nil
+			if gotErr != tt.wantErr {
+				t.Errorf("MinLen(%v)(%s) = %v, want %v", tt.length, tt.input, gotErr, tt.wantErr)
+			}
+		})
+	}
+}