Correctly interpret empty DocumentSymbol arrays

Author: cmaglie

lsp/protocol.go

@@ -264,6 +264,9 @@ func (entry *DocumentSymbolArrayOrSymbolInformationArray) UnmarshalJSON(raw []by
 	if err := json.Unmarshal(raw, &intermediate); err != nil {
 		return err
 	}
+	if len(intermediate) == 0 {
+		return nil
+	}
 	discriminator := struct {
 		Range    *Range    `json:"range,omitempty"`
 		Location *Location `json:"location,omitempty"`
@@ -292,6 +295,16 @@ func (entry *DocumentSymbolArrayOrSymbolInformationArray) UnmarshalJSON(raw []by
 	return nil
 }
 
+func (entry DocumentSymbolArrayOrSymbolInformationArray) MarshalJSON() ([]byte, error) {
+	if entry.DocumentSymbolArray != nil {
+		return json.Marshal(entry.DocumentSymbolArray)
+	}
+	if entry.SymbolInformationArray != nil {
+		return json.Marshal(entry.SymbolInformationArray)
+	}
+	return []byte("[]"), nil
+}
+
 // ApplyWorkspaceEditParams structure according to LSP
 type ApplyWorkspaceEditParams struct {
 	Label string        `json:"label,omitempty"`

lsp/protocol_test.go

@@ -159,4 +159,14 @@ func TestVariousMessages(t *testing.T) {
 		err := json.Unmarshal([]byte(msg), &symbol)
 		require.NoError(t, err)
 	})
+
+	t.Run("EmptyDocumentSymbolMarshalUnmarshal", func(t *testing.T) {
+		var symbol DocumentSymbolArrayOrSymbolInformationArray
+		err := json.Unmarshal([]byte(`[]`), &symbol)
+		require.NoError(t, err)
+		data, err := json.Marshal(symbol)
+		require.Equal(t, "[]", string(data))
+		data, err = json.Marshal(&symbol)
+		require.Equal(t, "[]", string(data))
+	})
 }