fix #2281: passthru escapes when parsing regex

Make the InfluxQL parser check for '\/' escape and pass all other
escapes through to the Go regexp parser unmodified.

influxql/scanner.go

@@ -183,7 +183,7 @@ func (s *Scanner) ScanRegex() (tok Token, pos Pos, lit string) {
 	// Valid escape chars.
 	escapes := map[rune]rune{'/': '/'}
 
-	b, err := ScanDelimited(s.r, start, end, escapes)
+	b, err := ScanDelimited(s.r, start, end, escapes, true)
 
 	if err == errBadEscape {
 		_, pos = s.r.curr()
@@ -443,7 +443,7 @@ func (r *reader) curr() (ch rune, pos Pos) {
 // eof is a marker code point to signify that the reader can't read any more.
 const eof = rune(0)
 
-func ScanDelimited(r io.RuneScanner, start, end rune, escapes map[rune]rune) ([]byte, error) {
+func ScanDelimited(r io.RuneScanner, start, end rune, escapes map[rune]rune, escapesPassThru bool) ([]byte, error) {
 	// Scan start delimiter.
 	if ch, _, err := r.ReadRune(); err != nil {
 		return nil, err
@@ -468,15 +468,23 @@ func ScanDelimited(r io.RuneScanner, start, end rune, escapes map[rune]rune) ([]
 				return nil, err
 			}
 
-			r, ok := escapes[ch1]
+			c, ok := escapes[ch1]
 			if !ok {
-				buf.Reset()
-				_, _ = buf.WriteRune(ch0)
-				_, _ = buf.WriteRune(ch1)
-				return buf.Bytes(), errBadEscape
+				if escapesPassThru {
+					// Unread ch1 (char after the \)
+					_ = r.UnreadRune()
+					// Write ch0 (\) to the output buffer.
+					_, _ = buf.WriteRune(ch0)
+					continue
+				} else {
+					buf.Reset()
+					_, _ = buf.WriteRune(ch0)
+					_, _ = buf.WriteRune(ch1)
+					return buf.Bytes(), errBadEscape
+				}
 			}
 
-			_, _ = buf.WriteRune(r)
+			_, _ = buf.WriteRune(c)
 		} else {
 			_, _ = buf.WriteRune(ch0)
 		}

influxql/scanner_test.go

@@ -258,3 +258,29 @@ func TestScanString(t *testing.T) {
 		}
 	}
 }
+
+// Test scanning regex
+func TestScanRegex(t *testing.T) {
+	var tests = []struct {
+		in  string
+		tok influxql.Token
+		lit string
+		err string
+	}{
+		{in: `/^payments\./`, tok: influxql.REGEX, lit: `^payments\.`},
+		{in: `/foo\/bar/`, tok: influxql.REGEX, lit: `foo/bar`},
+		{in: `/foo\\/bar/`, tok: influxql.REGEX, lit: `foo\/bar`},
+		{in: `/foo\\bar/`, tok: influxql.REGEX, lit: `foo\\bar`},
+	}
+
+	for i, tt := range tests {
+		s := influxql.NewScanner(strings.NewReader(tt.in))
+		tok, _, lit := s.ScanRegex()
+		if tok != tt.tok {
+			t.Errorf("%d. %s: error:\n\texp=%s\n\tgot=%s\n", i, tt.in, tt.tok.String(), tok.String())
+		}
+		if lit != tt.lit {
+			t.Errorf("%d. %s: error:\n\texp=%s\n\tgot=%s\n", i, tt.in, tt.lit, lit)
+		}
+	}
+}