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// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package match provides functions for performing filepath [?,*,**] wildcard
// matching.
package match
import (
"fmt"
"regexp"
"strings"
)
// Test is the match predicate returned by New.
type Test func(path string) bool
// New returns a Test function that returns true iff the path matches the
// provided pattern.
//
// pattern uses forward-slashes for directory separators '/', and may use the
// following wildcards:
// ? - matches any single non-separator character
// * - matches any sequence of non-separator characters
// ** - matches any sequence of characters including separators
func New(pattern string) (Test, error) {
// Transform pattern into a regex by replacing the uses of `?`, `*`, `**`
// with corresponding regex patterns.
// As the pattern may contain other regex sequences, the string has to be
// escaped. So:
// a) Replace the patterns of `?`, `*`, `**` with unique placeholder tokens.
// b) Escape the expression so that other sequences don't confuse the regex
// parser.
// c) Replace the placeholder tokens with the corresponding regex tokens.
// Temporary placeholder tokens
const (
starstar = "••"
star = "•"
questionmark = "¿"
)
// Check pattern doesn't contain any of our placeholder tokens
for _, r := range []rune{'•', '¿'} {
if strings.ContainsRune(pattern, r) {
return nil, fmt.Errorf("Pattern must not contain '%c'", r)
}
}
// Replace **, * and ? with placeholder tokens
subbed := pattern
subbed = strings.ReplaceAll(subbed, "**", starstar)
subbed = strings.ReplaceAll(subbed, "*", star)
subbed = strings.ReplaceAll(subbed, "?", questionmark)
// Escape any remaining regex characters
escaped := regexp.QuoteMeta(subbed)
// Insert regex matchers for the substituted tokens
regex := "^" + escaped + "$"
regex = strings.ReplaceAll(regex, starstar, ".*")
regex = strings.ReplaceAll(regex, star, "[^/]*")
regex = strings.ReplaceAll(regex, questionmark, "[^/]")
re, err := regexp.Compile(regex)
if err != nil {
return nil, fmt.Errorf(`Failed to compile regex "%v" for pattern "%v": %w`, regex, pattern, err)
}
return re.MatchString, nil
}