1 files changed, 83 insertions, 0 deletions

diff --git a/cli/internal/doublestar/validate.go b/cli/internal/doublestar/validate.go
new file mode 100644
index 0000000..225fc5e
--- /dev/null
+++ b/cli/internal/doublestar/validate.go
@@ -0,0 +1,83 @@
+// Package doublestar is adapted from https://github.com/bmatcuk/doublestar
+// Copyright Bob Matcuk. All Rights Reserved.
+// SPDX-License-Identifier: MIT
+package doublestar
+
+import "path/filepath"
+
+// ValidatePattern validates a pattern. Patterns are validated while they run in Match(),
+// PathMatch(), and Glob(), so, you normally wouldn't need to call this.
+// However, there are cases where this might be useful: for example, if your
+// program allows a user to enter a pattern that you'll run at a later time,
+// you might want to validate it.
+//
+// ValidatePattern assumes your pattern uses '/' as the path separator.
+func ValidatePattern(s string) bool {
+	return doValidatePattern(s, '/')
+}
+
+// ValidatePathPattern only uses your OS path separator. In other words, use
+// ValidatePattern if you would normally use Match() or Glob(). Use
+// ValidatePathPattern if you would normally use PathMatch(). Keep in mind,
+// Glob() requires '/' separators, even if your OS uses something else.
+func ValidatePathPattern(s string) bool {
+	return doValidatePattern(s, filepath.Separator)
+}
+
+func doValidatePattern(s string, separator rune) bool {
+	altDepth := 0
+	l := len(s)
+VALIDATE:
+	for i := 0; i < l; i++ {
+		switch s[i] {
+		case '\\':
+			if separator != '\\' {
+				// skip the next byte - return false if there is no next byte
+				if i++; i >= l {
+					return false
+				}
+			}
+			continue
+
+		case '[':
+			if i++; i >= l {
+				// class didn't end
+				return false
+			}
+			if s[i] == '^' || s[i] == '!' {
+				i++
+			}
+			if i >= l || s[i] == ']' {
+				// class didn't end or empty character class
+				return false
+			}
+
+			for ; i < l; i++ {
+				if separator != '\\' && s[i] == '\\' {
+					i++
+				} else if s[i] == ']' {
+					// looks good
+					continue VALIDATE
+				}
+			}
+
+			// class didn't end
+			return false
+
+		case '{':
+			altDepth++
+			continue
+
+		case '}':
+			if altDepth == 0 {
+				// alt end without a corresponding start
+				return false
+			}
+			altDepth--
+			continue
+		}
+	}
+
+	// valid as long as all alts are closed
+	return altDepth == 0
+}