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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cache
import (
"path"
"path/filepath"
"regexp"
"strings"
)
type Filterer struct {
// Whether a filter is excluded depends on the operator (first char of the raw filter).
// Slices filters and excluded then should have the same length.
filters []*regexp.Regexp
excluded []bool
}
// NewFilterer computes regular expression form of all raw filters
func NewFilterer(rawFilters []string) *Filterer {
var f Filterer
for _, filter := range rawFilters {
filter = path.Clean(filepath.ToSlash(filter))
// TODO(dungtuanle): fix: validate [+-] prefix.
op, prefix := filter[0], filter[1:]
// convertFilterToRegexp adds "/" at the end of prefix to handle cases where a filter is a prefix of another filter.
// For example, it prevents [+foobar, -foo] from excluding "foobar".
f.filters = append(f.filters, convertFilterToRegexp(filepath.ToSlash(prefix)))
f.excluded = append(f.excluded, op == '-')
}
return &f
}
// Disallow return true if the path is excluded from the filterer's filters.
func (f *Filterer) Disallow(path string) bool {
// Ensure trailing but not leading slash.
path = strings.TrimPrefix(path, "/")
if !strings.HasSuffix(path, "/") {
path += "/"
}
// TODO(adonovan): opt: iterate in reverse and break at first match.
excluded := false
for i, filter := range f.filters {
if filter.MatchString(path) {
excluded = f.excluded[i] // last match wins
}
}
return excluded
}
// convertFilterToRegexp replaces glob-like operator substrings in a string file path to their equivalent regex forms.
// Supporting glob-like operators:
// - **: match zero or more complete path segments
func convertFilterToRegexp(filter string) *regexp.Regexp {
if filter == "" {
return regexp.MustCompile(".*")
}
var ret strings.Builder
ret.WriteString("^")
segs := strings.Split(filter, "/")
for _, seg := range segs {
// Inv: seg != "" since path is clean.
if seg == "**" {
ret.WriteString(".*")
} else {
ret.WriteString(regexp.QuoteMeta(seg))
}
ret.WriteString("/")
}
pattern := ret.String()
// Remove unnecessary "^.*" prefix, which increased
// BenchmarkWorkspaceSymbols time by ~20% (even though
// filter CPU time increased by only by ~2.5%) when the
// default filter was changed to "**/node_modules".
pattern = strings.TrimPrefix(pattern, "^.*")
return regexp.MustCompile(pattern)
}
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