parser: fix line skipping when key is empty

error.go

@@ -32,3 +32,18 @@ func IsErrDelimiterNotFound(err error) bool {
 func (err ErrDelimiterNotFound) Error() string {
 	return fmt.Sprintf("key-value delimiter not found: %s", err.Line)
 }
+
+// ErrEmptyKeyName indicates the error type of no key name is found which there should be one.
+type ErrEmptyKeyName struct {
+	Line string
+}
+
+// IsErrEmptyKeyName returns true if the given error is an instance of ErrEmptyKeyName.
+func IsErrEmptyKeyName(err error) bool {
+	_, ok := err.(ErrEmptyKeyName)
+	return ok
+}
+
+func (err ErrEmptyKeyName) Error() string {
+	return fmt.Sprintf("empty key name: %s", err.Line)
+}

ini_test.go

@@ -445,6 +445,8 @@ BiomeRarityScale: 100
 
 BiomeGroup(NormalBiomes, 3, 99, RoofedForestEnchanted, ForestSakura, FloatingJungle
 BiomeGroup(IceBiomes, 4, 85, Ice Plains)
+
+= RainForest
 `))
 			require.NoError(t, err)
 			require.NotNil(t, f)

parser.go

@@ -164,6 +164,10 @@ func readKeyName(delimiters string, in []byte) (string, int, error) {
 	if endIdx < 0 {
 		return "", -1, ErrDelimiterNotFound{line}
 	}
+	if endIdx == 0 {
+		return "", -1, ErrEmptyKeyName{line}
+	}
+
 	return strings.TrimSpace(line[0:endIdx]), endIdx + 1, nil
 }
 
@@ -466,8 +470,9 @@ func (f *File) parse(reader io.Reader) (err error) {
 
 		kname, offset, err := readKeyName(f.options.KeyValueDelimiters, line)
 		if err != nil {
+			switch {
 			// Treat as boolean key when desired, and whole line is key name.
-			if IsErrDelimiterNotFound(err) {
+			case IsErrDelimiterNotFound(err):
 				switch {
 				case f.options.AllowBooleanKeys:
 					kname, err := p.readValue(line, parserBufferSize)
@@ -485,6 +490,8 @@ func (f *File) parse(reader io.Reader) (err error) {
 				case f.options.SkipUnrecognizableLines:
 					continue
 				}
+			case IsErrEmptyKeyName(err) && f.options.SkipUnrecognizableLines:
+				continue
 			}
 			return err
 		}