🐛 parsing erroneous files yields an exception (#366)

src/json.hpp

@@ -7597,6 +7597,12 @@ class basic_json
         explicit lexer(std::istream& s)
             : m_stream(&s), m_line_buffer()
         {
+            // immediately abort if stream is erroneous
+            if (s.fail())
+            {
+                throw std::invalid_argument("stream error: " +  std::string(strerror(errno)));
+            }
+
             // fill buffer
             fill_line_buffer();
 

src/json.hpp.re2c

@@ -7597,6 +7597,12 @@ class basic_json
         explicit lexer(std::istream& s)
             : m_stream(&s), m_line_buffer()
         {
+            // immediately abort if stream is erroneous
+            if (s.fail())
+            {
+                throw std::invalid_argument("stream error: " +  std::string(strerror(errno)));
+            }
+
             // fill buffer
             fill_line_buffer();
 

test/src/unit-regression.cpp

@@ -495,4 +495,10 @@ TEST_CASE("regression tests")
         json j = json::parse("22e2222");
         CHECK(j == json());
     }
+
+    SECTION("issue #366 - json::parse on failed stream gets stuck")
+    {
+        std::ifstream f("file_not_found.json");
+        CHECK_THROWS_AS(json::parse(f), std::invalid_argument);
+    }
 }