Empty highlighting for unknown filetypes

internal/buffer/buffer.go

@@ -610,8 +610,12 @@ func (b *Buffer) UpdateRules() {
 	}
 
 	if b.Highlighter == nil || syntaxFile != "" {
-		if b.SyntaxDef != nil {
 		b.Settings["filetype"] = b.SyntaxDef.FileType
+	} else {
+		b.SyntaxDef = &highlight.EmptyDef
+	}
+
+	if b.SyntaxDef != nil {
 		b.Highlighter = highlight.NewHighlighter(b.SyntaxDef)
 		if b.Settings["syntax"].(bool) {
 			b.Highlighter.HighlightStates(b)
@@ -619,7 +623,6 @@ func (b *Buffer) UpdateRules() {
 		}
 	}
 }
-}
 
 // ClearMatches clears all of the syntax highlighting for the buffer
 func (b *Buffer) ClearMatches() {

pkg/highlight/highlighter.go

@@ -68,6 +68,8 @@ func combineLineMatch(src, dst LineMatch) LineMatch {
 // A State represents the region at the end of a line
 type State *region
 
+var EmptyDef = Def{nil, &rules{}}
+
 // LineStates is an interface for a buffer-like object which can also store the states and matches for every line
 type LineStates interface {
 	LineBytes(n int) []byte