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rules.go
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rules.go
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// SPDX-FileCopyrightText: 2022 SAP SE or an SAP affiliate company and Open Component Model contributors.
//
// SPDX-License-Identifier: Apache-2.0
package ignore
import (
"bufio"
"bytes"
"fmt"
"io"
"log"
"os"
"strings"
"github.com/mandelsoft/filepath/pkg/filepath"
"github.com/mandelsoft/vfs/pkg/vfs"
"github.com/pkg/errors"
)
// HelmIgnore default name of an ignorefile.
const HelmIgnore = ".helmignore"
// Rules is a collection of path matching rules.
//
// Parse() and ParseFile() will construct and populate new Rules.
// Empty() will create an immutable empty ruleset.
type Rules struct {
patterns []*pattern
}
// Empty builds an empty ruleset.
func Empty() *Rules {
return &Rules{patterns: []*pattern{}}
}
// AddDefaults adds default ignore patterns.
//
// Ignore all dotfiles in "templates/".
func (r *Rules) AddDefaults() {
r.parseRule(`templates/.?*`)
}
// ParseFile parses a helmignore file and returns the *Rules.
func ParseFile(file string, fss ...vfs.FileSystem) (*Rules, error) {
f, err := os.Open(file)
if err != nil {
return nil, err
}
defer f.Close()
return Parse(f)
}
// Parse parses a rules file.
func Parse(file io.Reader) (*Rules, error) {
r := &Rules{patterns: []*pattern{}}
s := bufio.NewScanner(file)
currentLine := 0
utf8bom := []byte{0xEF, 0xBB, 0xBF}
for s.Scan() {
scannedBytes := s.Bytes()
// We trim UTF8 BOM
if currentLine == 0 {
scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)
}
line := string(scannedBytes)
currentLine++
if err := r.parseRule(line); err != nil {
return r, err
}
}
return r, s.Err()
}
// Ignore evaluates the file at the given path, and returns true if it should be ignored.
//
// Ignore evaluates path against the rules in order. Evaluation stops when a match
// is found. Matching a negative rule will stop evaluation.
func (r *Rules) Ignore(path string, fi os.FileInfo) bool {
// Don't match on empty dirs.
if path == "" {
return false
}
// Disallow ignoring the current working directory.
// See issue:
// 1776 (New York City) Hamilton: "Pardon me, are you Aaron Burr, sir?"
if path == "." || path == "./" {
return false
}
for _, p := range r.patterns {
if p.match == nil {
log.Printf("ignore: no matcher supplied for %q", p.raw)
return false
}
// For negative rules, we need to capture and return non-matches,
// and continue for matches.
if p.negate {
if p.mustDir && !fi.IsDir() {
return true
}
if !p.match(path, fi) {
return true
}
continue
}
// If the rule is looking for directories, and this is not a directory,
// skip it.
if p.mustDir && !fi.IsDir() {
continue
}
if p.match(path, fi) {
return true
}
}
return false
}
// parseRule parses a rule string and creates a pattern, which is then stored in the Rules object.
func (r *Rules) parseRule(rule string) error {
rule = strings.TrimSpace(rule)
// Ignore blank lines
if rule == "" {
return nil
}
// Comment
if strings.HasPrefix(rule, "#") {
return nil
}
// Fail any rules that contain **
if strings.Contains(rule, "**") {
return errors.New("double-star (**) syntax is not supported")
}
// Fail any patterns that can't compile. A non-empty string must be
// given to Match() to avoid optimization that skips rule evaluation.
if _, err := filepath.Match(rule, "abc"); err != nil {
return fmt.Errorf("failed to match rule: %w", err)
}
p := &pattern{raw: rule}
// Negation is handled at a higher level, so strip the leading ! from the
// string.
if strings.HasPrefix(rule, "!") {
p.negate = true
rule = rule[1:]
}
// Directory verification is handled by a higher level, so the trailing /
// is removed from the rule. That way, a directory named "foo" matches,
// even if the supplied string does not contain a literal slash character.
if strings.HasSuffix(rule, "/") {
p.mustDir = true
rule = strings.TrimSuffix(rule, "/")
}
switch {
case strings.HasPrefix(rule, "/"):
// Require path matches the root path.
p.match = func(n string, _ os.FileInfo) bool {
rule = strings.TrimPrefix(rule, "/")
ok, err := filepath.Match(rule, n)
if err != nil {
log.Printf("Failed to compile %q: %s", rule, err)
return false
}
return ok
}
case strings.Contains(rule, "/"):
// require structural match.
p.match = func(n string, _ os.FileInfo) bool {
ok, err := filepath.Match(rule, n)
if err != nil {
log.Printf("Failed to compile %q: %s", rule, err)
return false
}
return ok
}
default:
p.match = func(n string, _ os.FileInfo) bool {
// When there is no slash in the pattern, we evaluate ONLY the
// filename.
n = filepath.Base(n)
ok, err := filepath.Match(rule, n)
if err != nil {
log.Printf("Failed to compile %q: %s", rule, err)
return false
}
return ok
}
}
r.patterns = append(r.patterns, p)
return nil
}
// matcher is a function capable of computing a match.
//
// It returns true if the rule matches.
type matcher func(name string, fi os.FileInfo) bool
// pattern describes a pattern to be matched in a rule set.
type pattern struct {
// raw is the unparsed string, with nothing stripped.
raw string
// match is the matcher function.
match matcher
// negate indicates that the rule's outcome should be negated.
negate bool
// mustDir indicates that the matched file must be a directory.
mustDir bool
}