Provide token friendly names in err messages

Author: yhabteab

internal/filter/lexer.go

@@ -14,6 +14,21 @@ import (
 // Currently, it allows to match any character except a LogicalOp and CompOperator.
 var identifiersMatcher = regexp.MustCompile("[^!&|~<>=()]")
 
+// tokenDisplayNames contains a list of all the defined parser tokens and their respective
+// friendly names used to output in error messages.
+var tokenDisplayNames = map[string]string{
+	"$unk":                    "\"unknown\"",
+	"T_EQUAL":                 "\"=\"",
+	"T_UNEQUAL":               "\"!=\"",
+	"T_LIKE":                  "\"~\"",
+	"T_UNLIKE":                "\"!~\"",
+	"T_LESS_THAN":             "\"<\"",
+	"T_GREATER_THAN":          "\">\"",
+	"T_LESS_THAN_OR_EQUAL":    "\"<=\"",
+	"T_GREATER_THAN_OR_EQUAL": "\">=\"",
+	"T_IDENTIFIER":            "\"column or value\"",
+}
+
 // init just sets the global yyErrorVerbose variable to true.
 func init() {
 	// Enable parsers error verbose to get more context of the parsing failures
@@ -139,6 +154,11 @@ func (l *Lexer) Lex(yyval *yySymType) int {
 // our lexer with some additional context instead. This function then wraps the provided err
 // and adds line, column number and offset to the error string.
 func (l *Lexer) Error(s string) {
+	// Replace all parser token names by their corresponding friendly names.
+	for token, name := range tokenDisplayNames {
+		s = strings.ReplaceAll(s, token, name)
+	}
+
 	l.err = fmt.Errorf("%d:%d (%d): %s", l.Line, l.Column, l.Offset, s)
 
 	// Always reset the current filter rule when encountering an error.

internal/filter/parser_test.go

@@ -14,13 +14,13 @@ func TestParser(t *testing.T) {
 		t.Parallel()
 
 		_, err := Parse("(a=b|c=d)e=f")
-		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected T_IDENTIFIER")
+		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \"column or value\"")
 
 		_, err = Parse("(a=b|c=d|)e=f")
-		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \")\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \")\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("col=(")
-		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected \"(\", expecting T_IDENTIFIER")
+		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected \"(\", expecting \"column or value\"")
 
 		_, err = Parse("(((x=a)&y=b")
 		assert.EqualError(t, err, "1:12 (11): syntax error: unexpected $end, expecting \")\"")
@@ -29,10 +29,10 @@ func TestParser(t *testing.T) {
 		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \")\"")
 
 		_, err = Parse("!(&")
-		assert.EqualError(t, err, "1:3 (2): syntax error: unexpected \"&\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:3 (2): syntax error: unexpected \"&\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("foo&bar=(te(st)")
-		assert.EqualError(t, err, "1:9 (8): syntax error: unexpected \"(\", expecting T_IDENTIFIER")
+		assert.EqualError(t, err, "1:9 (8): syntax error: unexpected \"(\", expecting \"column or value\"")
 
 		_, err = Parse("foo&bar=te(st)")
 		assert.EqualError(t, err, "1:11 (10): syntax error: unexpected \"(\"")
@@ -41,37 +41,37 @@ func TestParser(t *testing.T) {
 		assert.EqualError(t, err, "1:13 (12): syntax error: unexpected \")\"")
 
 		_, err = Parse("!()|&()&)")
-		assert.EqualError(t, err, "1:3 (2): syntax error: unexpected \")\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:3 (2): syntax error: unexpected \")\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("=foo")
-		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected T_EQUAL, expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"=\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("foo>")
-		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected $end, expecting T_IDENTIFIER")
+		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected $end, expecting \"column or value\"")
 
 		_, err = Parse("foo==")
-		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected T_EQUAL, expecting T_IDENTIFIER")
+		assert.EqualError(t, err, "1:5 (4): syntax error: unexpected \"=\", expecting \"column or value\"")
 
 		_, err = Parse("=>foo")
-		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected T_EQUAL, expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"=\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("&foo")
-		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"&\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"&\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("&&foo")
-		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"&\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:1 (0): syntax error: unexpected \"&\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("(&foo=bar)")
-		assert.EqualError(t, err, "1:2 (1): syntax error: unexpected \"&\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:2 (1): syntax error: unexpected \"&\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("(foo=bar|)")
-		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \")\", expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:10 (9): syntax error: unexpected \")\", expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("((((((")
-		assert.EqualError(t, err, "1:7 (6): syntax error: unexpected $end, expecting T_IDENTIFIER or \"(\"")
+		assert.EqualError(t, err, "1:7 (6): syntax error: unexpected $end, expecting \"column or value\" or \"(\"")
 
 		_, err = Parse("foo&bar&col=val!=val")
-		assert.EqualError(t, err, "1:17 (16): syntax error: unexpected T_UNEQUAL")
+		assert.EqualError(t, err, "1:17 (16): syntax error: unexpected \"!=\"")
 
 		_, err = Parse("col%7umn")
 		assert.EqualError(t, err, "invalid URL escape \"%7u\"")