Optimize string field accumulation to do fewer allocations

alecthomas · Dec 5, 2022 · d03a0d2 · d03a0d2
1 parent 3de599c
commit d03a0d2
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/nodes.go b/nodes.go
@@ -734,9 +734,14 @@ func setField(tokens []lexer.Token, strct reflect.Value, field structLexerField,
 		if err != nil {
 			return err
 		}
+		if len(fieldValue) == 0 {
+			return nil
+		}
+		accumulated := f.String()
 		for _, v := range fieldValue {
-			f.Set(reflect.ValueOf(f.String() + v.String()).Convert(f.Type()))
+			accumulated += v.String()
 		}
+		f.SetString(accumulated)
 		return nil
 	}
 

diff --git a/parser_test.go b/parser_test.go
@@ -201,8 +201,9 @@ func TestRepetitionAcrossFields(t *testing.T) {
 }
 
 func TestAccumulateString(t *testing.T) {
+	type customString string
 	type testAccumulateString struct {
-		A string `@"."+`
+		A customString `@"."+`
 	}
 
 	parser := mustTestParser[testAccumulateString](t)