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Return a useful Got when Regexp fails

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This commit is contained in:
Brandon Dyck 2024-09-11 14:43:33 -06:00
parent ee544cd121
commit 1f746ae6de
2 changed files with 13 additions and 5 deletions
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17
bytes/regexp.go
View File

@ -16,11 +16,12 @@ import (
// with the regexp package.
type RuneReader struct {
cursor cursor.Cursor[byte]
start uint64
err error
}
func NewRuneReader(c cursor.Cursor[byte]) *RuneReader {
return &RuneReader{cursor: c}
return &RuneReader{cursor: c, start: c.Pos()}
}
func (rr *RuneReader) ReadRune() (r rune, size int, err error) {
@ -48,6 +49,10 @@ func (rr *RuneReader) Error() error {
return rr.err
}
func (rr *RuneReader) Count() uint64 {
return rr.cursor.Pos() - rr.start
}
func Regexp(str string) gigaparsec.Parser[byte, string] {
if !strings.HasPrefix(str, "^") && !strings.HasPrefix(str, `\A`) {
str = "^" + str
@ -62,12 +67,15 @@ func Regexp(str string) gigaparsec.Parser[byte, string] {
return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: reader error: %w", err)
}
if idx == nil {
got := make([]byte, r.Count())
_, _, err = input.Cursor().Read(got)
if err != nil {
return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: unexpected error: %w", err)
}
return gigaparsec.Fail[byte, string](false, gigaparsec.Message{
Pos: input.Pos(),
Got: string(got),
Expected: []string{expected},
// TODO Not having a Got is unsatisfactory, but how do I extract useful information?
// Maybe just read a fixed number of bytes or to the end, whichever comes first?
// I could add extra methods to cursor.RuneReader to figure out how much it had read.
}), nil
}
// Alas, this is a little wasteful because a Regexp can only return indices
@ -75,7 +83,6 @@ func Regexp(str string) gigaparsec.Parser[byte, string] {
dst := make([]byte, idx[1]-idx[0])
n, _, err := input.Cursor().Read(dst)
if err != nil {
// If we can't access those same bytes again, something is wrong.
return gigaparsec.Result[byte, string]{}, fmt.Errorf("Regexp: unexpected error: %w", err)
}
next := input.At(input.Pos() + n)

1
bytes/regexp_test.go
View File

@ -10,6 +10,7 @@ func TestRegexp(t *testing.T) {
t.Run("only searches the beginning of input", Todo)
t.Run("position is correct after match", Todo)
t.Run("fails on unexpected error", Todo)
t.Run("returns a useful Got value", Todo)
}
func TestRuneReader(t *testing.T) {