From 64c6cf44732d889b8844c8f73b7b67e0383b23f4 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Fri, 18 Oct 2019 11:28:59 -0700
Subject: [PATCH] Implicitly reset parser's state if language is changed after
 a timeout

---
 cli/src/tests/parser_test.rs | 51 ++++++++++++++++++++++++++++++++++++
 lib/src/parser.c             |  5 ++--
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/cli/src/tests/parser_test.rs b/cli/src/tests/parser_test.rs
index dc25e081..c9249eb8 100644
--- a/cli/src/tests/parser_test.rs
+++ b/cli/src/tests/parser_test.rs
@@ -1,3 +1,4 @@
+use super::helpers::allocations;
 use super::helpers::edits::ReadRecorder;
 use super::helpers::fixtures::{get_language, get_test_language};
 use crate::generate::generate_parser_for_grammar;
@@ -567,6 +568,56 @@ fn test_parsing_with_a_timeout_and_a_reset() {
     );
 }
 
+#[test]
+fn test_parsing_with_a_timeout_and_implicit_reset() {
+    allocations::record(|| {
+        let mut parser = Parser::new();
+        parser.set_language(get_language("javascript")).unwrap();
+
+        parser.set_timeout_micros(5);
+        let tree = parser.parse(
+            "[\"ok\", 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]",
+            None,
+        );
+        assert!(tree.is_none());
+
+        // Changing the parser's language implicitly resets, discarding
+        // the previous partial parse.
+        parser.set_language(get_language("json")).unwrap();
+        parser.set_timeout_micros(0);
+        let tree = parser.parse(
+            "[null, 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]",
+            None,
+        ).unwrap();
+        assert_eq!(
+            tree.root_node()
+                .named_child(0)
+                .unwrap()
+                .named_child(0)
+                .unwrap()
+                .kind(),
+            "null"
+        );
+    });
+}
+
+#[test]
+fn test_parsing_with_timeout_and_no_completion() {
+    allocations::record(|| {
+        let mut parser = Parser::new();
+        parser.set_language(get_language("javascript")).unwrap();
+
+        parser.set_timeout_micros(5);
+        let tree = parser.parse(
+            "[\"ok\", 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]",
+            None,
+        );
+        assert!(tree.is_none());
+
+        // drop the parser when it has an unfinished parse
+    });
+}
+
 // Included Ranges
 
 #[test]
diff --git a/lib/src/parser.c b/lib/src/parser.c
index 88b20845..35772ed0 100644
--- a/lib/src/parser.c
+++ b/lib/src/parser.c
@@ -1655,6 +1655,7 @@ TSParser *ts_parser_new(void) {
 void ts_parser_delete(TSParser *self) {
   if (!self) return;
 
+  ts_parser_set_language(self, NULL);
   ts_stack_delete(self->stack);
   if (self->reduce_actions.contents) {
     array_delete(&self->reduce_actions);
@@ -1670,7 +1671,6 @@ void ts_parser_delete(TSParser *self) {
   ts_parser__set_cached_token(self, 0, NULL_SUBTREE, NULL_SUBTREE);
   ts_subtree_pool_delete(&self->tree_pool);
   reusable_node_delete(&self->reusable_node);
-  ts_parser_set_language(self, NULL);
   ts_free(self);
 }
 
@@ -1695,6 +1695,7 @@ bool ts_parser_set_language(TSParser *self, const TSLanguage *language) {
   }
 
   self->language = language;
+  ts_parser_reset(self);
   return true;
 }
 
@@ -1747,7 +1748,7 @@ const TSRange *ts_parser_included_ranges(const TSParser *self, uint32_t *count)
 }
 
 void ts_parser_reset(TSParser *self) {
-  if (self->language->external_scanner.deserialize) {
+  if (self->language && self->language->external_scanner.deserialize) {
     self->language->external_scanner.deserialize(self->external_scanner_payload, NULL, 0);
   }