Symbol grammar clarifications (#255)

- Forbids scheme from being empty or starting with 'local'
- Unifies "any UTF-8" wording
- Specifies that identifiers that can be encoded as simple identifiers have to be encoded as simple identifiers
- Makes method_disambiguator optional

Co-authored-by: Varun Gandhi <varun.gandhi@sourcegraph.com>

Author: Christoph Hegemann

bindings/go/scip/scip.pb.go

@@ -3,7 +3,6 @@ package scip
 import (
 	"fmt"
 	"strings"
-	"unicode"
 
 	"github.com/sourcegraph/sourcegraph/lib/errors"
 )
@@ -22,10 +21,13 @@ func IsLocalSymbol(symbol string) bool {
 	return strings.HasPrefix(symbol, "local ")
 }
 
+func isSimpleIdentifierCharacter(c rune) bool {
+	return c == '_' || c == '+' || c == '-' || c == '$' || ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9')
+}
+
 func isSimpleIdentifier(s string) bool {
 	for _, c := range s {
-		if ('0' <= c && c <= '9') || ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') ||
-			c == '$' || c == '+' || c == '-' || c == '_' {
+		if isSimpleIdentifierCharacter(c) {
 			continue
 		}
 		return false
@@ -218,7 +220,7 @@ func (s *symbolParser) acceptIdentifier(what string) (string, error) {
 		return s.acceptBacktickEscapedIdentifier(what)
 	}
 	start := s.index
-	for s.index < len(s.Symbol) && isIdentifierCharacter(s.current()) {
+	for s.index < len(s.Symbol) && isSimpleIdentifierCharacter(s.current()) {
 		s.index++
 	}
 	if start == s.index {
@@ -227,10 +229,6 @@ func (s *symbolParser) acceptIdentifier(what string) (string, error) {
 	return string(s.Symbol[start:s.index]), nil
 }
 
-func isIdentifierCharacter(r rune) bool {
-	return unicode.IsLetter(r) || unicode.IsDigit(r) || r == '-' || r == '+' || r == '$' || r == '_'
-}
-
 func (s *symbolParser) acceptSpaceEscapedIdentifier(what string) (string, error) {
 	return s.acceptEscapedIdentifier(what, ' ')
 }

bindings/go/scip/symbol.go

@@ -139,7 +139,7 @@ func writeEscapedPackage(b *strings.Builder, name string) {
 func writeSuffixedDescriptor(b *strings.Builder, identifier string, suffixes ...rune) {
 	escape := false
 	for _, ch := range identifier {
-		if !isIdentifierCharacter(ch) {
+		if !isSimpleIdentifierCharacter(ch) {
 			escape = true
 			break
 		}

bindings/go/scip/symbol_formatter.go

@@ -88,6 +88,7 @@ func TestParseSymbolError(t *testing.T) {
 		"lsif-java maven package 1.0.0",
 		"lsif-java maven package 1.0.0 java/io/File#Entry.trailingstring",
 		"lsif-java maven package 1.0.0 java/io/File#Entry.unrecognizedSuffix@",
+		"lsif-java maven package 1.0.0 java/io/File#Entry.nonSimpλeIdentifier.",
 		"local 🧠",
 		"local ",
 		"local &&&",