kubernetes/staging/src/k8s.io/apiserver/pkg/cel/escaping.go

var celReservedSymbols …

var expandMatcher …

// newCharacterFilter returns a boolean array to indicate the allowed characters
func newCharacterFilter(characters string) []bool { … }

type escapeCheck …

// skipRegexCheck checks if escape would be skipped.
// if invalidCharFound is true, it must have invalid character; if invalidCharFound is false, not sure if it has invalid character or not
func skipRegexCheck(ident string) escapeCheck { … }

var validCharacterFilter …

// Escape escapes ident and returns a CEL identifier (of the form '[a-zA-Z_][a-zA-Z0-9_]*'), or returns
// false if the ident does not match the supported input format of `[a-zA-Z_.-/][a-zA-Z0-9_.-/]*`.
// Escaping Rules:
//   - '__' escapes to '__underscores__'
//   - '.' escapes to '__dot__'
//   - '-' escapes to '__dash__'
//   - '/' escapes to '__slash__'
//   - Identifiers that exactly match a CEL RESERVED keyword escape to '__{keyword}__'. The keywords are: "true", "false",
//     "null", "in", "as", "break", "const", "continue", "else", "for", "function", "if", "import", "let", loop", "package",
//     "namespace", "return".
func Escape(ident string) (string, bool) { … }

var unexpandMatcher …

// Unescape unescapes an CEL identifier containing the escape sequences described in Escape, or return false if the
// string contains invalid escape sequences. The escaped input is expected to be a valid CEL identifier, but is
// not checked.
func Unescape(escaped string) (string, bool) { … }