From df223d566e464c0dc234e816811d19c32be943b7 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Tue, 25 Feb 2014 18:32:17 -0800
Subject: [PATCH] Fix bug in parser error handling

---
 include/tree_sitter/parser.h | 26 ++++++++++++--------------
 spec/runtime/json_spec.cpp   | 10 ++++++++++
 src/runtime/tree.cpp         |  2 ++
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/include/tree_sitter/parser.h b/include/tree_sitter/parser.h
index b871e993..8b3dba7b 100644
--- a/include/tree_sitter/parser.h
+++ b/include/tree_sitter/parser.h
@@ -45,7 +45,6 @@ typedef struct {
     ts_state lex_state;
     ts_stack_entry *stack;
     size_t stack_size;
-    ts_tree *result;
 } ts_parser;
 
 static void ts_lex(ts_parser *parser);
@@ -58,7 +57,6 @@ static ts_parser ts_parser_make(const char *input) {
         .lex_state = 0,
         .stack = calloc(INITIAL_STACK_SIZE, sizeof(ts_stack_entry)),
         .stack_size = 0,
-        .result = NULL,
     };
     return result;
 }
@@ -123,7 +121,7 @@ static void ts_parser_reduce(ts_parser *parser, ts_symbol symbol, int immediate_
 
 static void ts_parser_advance(ts_parser *parser, ts_state lex_state) {
     DEBUG_LEX("character: '%c' \n", ts_parser_lookahead_char(parser));
-    if (ts_parser_lookahead_char(parser) != '\0')
+    if (ts_parser_lookahead_char(parser))
         parser->position++;
     parser->lex_state = lex_state;
 }
@@ -143,14 +141,11 @@ static void ts_parser_skip_whitespace(ts_parser *parser) {
         parser->position++;
 }
  
-static void ts_parser_handle_error(ts_parser *parser, size_t count, const ts_symbol *expected_symbols) {
-    if (parser->error_mode) {
-        parser->lex_state = ts_lex_state_error;
-        ts_lex(parser);
-    } else {
-        parser->error_mode = 1;
-        parser->lookahead_node = ts_tree_make_error(ts_parser_lookahead_char(parser), count, expected_symbols);
-    }
+static int ts_parser_handle_error(ts_parser *parser, size_t count, const ts_symbol *expected_symbols) {
+    parser->error_mode = 1;
+    ts_tree *error = ts_tree_make_error(ts_parser_lookahead_char(parser), count, expected_symbols);
+    parser->stack[0].node = error;
+    return 0;
 }
 
 #pragma mark - DSL
@@ -220,9 +215,12 @@ goto next_state; \
     
 #define PARSE_ERROR(count, inputs) \
 { \
-static const ts_symbol expected_inputs[] = inputs; \
-ts_parser_handle_error(parser, count, expected_inputs); \
-goto next_state; \
+    static const ts_symbol expected_inputs[] = inputs; \
+    if (ts_parser_handle_error(parser, count, expected_inputs)) { \
+        goto next_state; \
+    } else { \
+        goto done; \
+    } \
 }
 
 #define LEX_PANIC() \
diff --git a/spec/runtime/json_spec.cpp b/spec/runtime/json_spec.cpp
index f19d590e..8296eab3 100644
--- a/spec/runtime/json_spec.cpp
+++ b/spec/runtime/json_spec.cpp
@@ -48,6 +48,16 @@ describe("json", []() {
         ts_document_set_text(doc, "[1, 2, 3]");
         AssertThat(string(ts_document_string(doc)), Equals("(value (array (value (number)) (value (number)) (value (number))))"));
     });
+    
+    describe("errors", [&]() {
+        it("reports errors in the top-level node", [&]() {
+            ts_document_set_text(doc, "[");
+            AssertThat(string(ts_document_string(doc)), Equals("(ERROR)"));
+
+            ts_document_set_text(doc, "{ \"key1\": 1, ");
+            AssertThat(string(ts_document_string(doc)), Equals("(ERROR)"));
+        });
+    });
 });
 
 END_TEST
\ No newline at end of file
diff --git a/src/runtime/tree.cpp b/src/runtime/tree.cpp
index 05771569..f7e5e010 100644
--- a/src/runtime/tree.cpp
+++ b/src/runtime/tree.cpp
@@ -33,6 +33,7 @@ ts_tree * ts_tree_make_node(ts_symbol symbol, size_t child_count, ts_tree **chil
 
 ts_tree * ts_tree_make_error(char lookahead_char, size_t expected_input_count, const ts_symbol *expected_inputs) {
     ts_tree *result = new ts_tree();
+    result->symbol = ts_symbol_error;
     result->data.error = {
         .lookahead_char = lookahead_char,
         .expected_input_count = expected_input_count,
@@ -84,6 +85,7 @@ size_t ts_tree_child_count(const ts_tree *tree) {
 
 static string __tree_to_string(const ts_tree *tree, const char **symbol_names) {
     if (!tree) return "#<null-tree>";
+    if (tree->symbol == ts_symbol_error) return "(ERROR)";
     string result = string("(") + symbol_names[tree->symbol];
     for (int i = 0; i < tree->data.children.count; i++)
         result += " " + __tree_to_string(tree->data.children.contents[i], symbol_names);