From 46dcd530900215deb3e26c85da3fd472cdb38a4a Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Wed, 24 Jan 2018 14:04:55 -0800
Subject: [PATCH] Do not insert missing tokens if halt_on_error option is
 passed

---
 src/runtime/parser.c          | 26 +++++++++++---------------
 test/runtime/document_test.cc | 27 +++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/src/runtime/parser.c b/src/runtime/parser.c
index 81bed445..97098c98 100644
--- a/src/runtime/parser.c
+++ b/src/runtime/parser.c
@@ -208,10 +208,9 @@ static bool parser__better_version_exists(Parser *self, StackVersion version,
   return false;
 }
 
-static bool parser__condense_stack(Parser *self) {
+static unsigned parser__condense_stack(Parser *self) {
   bool made_changes = false;
   unsigned min_error_cost = UINT_MAX;
-  bool all_versions_have_error = true;
   for (StackVersion i = 0; i < ts_stack_version_count(self->stack); i++) {
     if (ts_stack_is_halted(self->stack, i)) {
       ts_stack_remove_version(self->stack, i);
@@ -225,8 +224,9 @@ static bool parser__condense_stack(Parser *self) {
       .dynamic_precedence = ts_stack_dynamic_precedence(self->stack, i),
       .is_in_error = ts_stack_top_state(self->stack, i) == ERROR_STATE,
     };
-    if (!status_i.is_in_error) all_versions_have_error = false;
-    if (status_i.cost < min_error_cost) min_error_cost = status_i.cost;
+    if (!status_i.is_in_error && status_i.cost < min_error_cost) {
+      min_error_cost = status_i.cost;
+    }
 
     for (StackVersion j = 0; j < i; j++) {
       ErrorStatus status_j = {
@@ -291,9 +291,7 @@ static bool parser__condense_stack(Parser *self) {
     LOG_STACK();
   }
 
-  return
-    (all_versions_have_error && ts_stack_version_count(self->stack) > 0) ||
-    (self->finished_tree && self->finished_tree->error_cost < min_error_cost);
+  return min_error_cost;
 }
 
 static void parser__restore_external_scanner(Parser *self, Tree *external_token) {
@@ -1239,14 +1237,12 @@ Tree *parser_parse(Parser *self, TSInput input, Tree *old_tree, bool halt_on_err
 
     self->reusable_node = reusable_node;
 
-    bool should_halt = parser__condense_stack(self);
-    if (should_halt) {
-      if (self->finished_tree) {
-        break;
-      } else if (halt_on_error) {
-        parser__halt_parse(self);
-        break;
-      }
+    unsigned min_error_cost = parser__condense_stack(self);
+    if (self->finished_tree && self->finished_tree->error_cost < min_error_cost) {
+      break;
+    } else if (halt_on_error && min_error_cost > 0) {
+      parser__halt_parse(self);
+      break;
     }
 
     self->in_ambiguity = version > 1;
diff --git a/test/runtime/document_test.cc b/test/runtime/document_test.cc
index 9cf5a14c..7c4bad6c 100644
--- a/test/runtime/document_test.cc
+++ b/test/runtime/document_test.cc
@@ -439,6 +439,33 @@ describe("Document", [&]() {
       AssertThat(ts_node_end_byte(root), Equals(input_string.size()));
     });
 
+    it("does not insert missing tokens if the halt_on_error flag is set", [&]() {
+      string input_string = "[1, null, 3";
+      ts_document_set_language(document, load_real_language("json"));
+      ts_document_set_input_string(document, input_string.c_str());
+
+      TSParseOptions options = {};
+      options.changed_ranges = nullptr;
+
+      options.halt_on_error = false;
+      ts_document_parse_with_options(document, options);
+      root = ts_document_root_node(document);
+      assert_node_string_equals(
+        root,
+        "(value (array (number) (null) (number) (MISSING)))");
+
+      ts_document_invalidate(document);
+
+      options.halt_on_error = true;
+      ts_document_parse_with_options(document, options);
+      root = ts_document_root_node(document);
+      assert_node_string_equals(
+        root,
+        "(ERROR (number) (null) (number))");
+
+      AssertThat(ts_node_end_byte(root), Equals(input_string.size()));
+    });
+
     it("can parse valid code with the halt_on_error flag set", [&]() {
       string input_string = "[1, null, 3]";
       ts_document_set_language(document, load_real_language("json"));