Set eofbit on exhausted input stream.

Fix issue #1340.

        The eofbit is set manually since we don't go through the
	stream interface. We could maybe use the stream interface
	instead, but there are some assumptions regarding which
	exception go through, so this seems to be the most prudent
	approach for now.

include/nlohmann/detail/input/input_adapters.hpp

@@ -60,8 +60,8 @@ class input_stream_adapter : public input_adapter_protocol
     ~input_stream_adapter() override
     {
         // clear stream flags; we use underlying streambuf I/O, do not
-        // maintain ifstream flags
-        is.clear();
+        // maintain ifstream flags, except eof
+        is.clear(is.rdstate() & std::ios::eofbit);
     }
 
     explicit input_stream_adapter(std::istream& i)
@@ -79,7 +79,11 @@ class input_stream_adapter : public input_adapter_protocol
     // end up as the same value, eg. 0xFFFFFFFF.
     std::char_traits<char>::int_type get_character() override
     {
-        return sb.sbumpc();
+        auto res = sb.sbumpc();
+        // set eof manually, as we don't use the istream interface.
+        if (res == EOF)
+            is.clear(is.rdstate() | std::ios::eofbit);
+        return res;
     }
 
   private:

single_include/nlohmann/json.hpp

@@ -2109,8 +2109,8 @@ class input_stream_adapter : public input_adapter_protocol
     ~input_stream_adapter() override
     {
         // clear stream flags; we use underlying streambuf I/O, do not
-        // maintain ifstream flags
-        is.clear();
+        // maintain ifstream flags, except eof
+        is.clear(is.rdstate() & std::ios::eofbit);
     }
 
     explicit input_stream_adapter(std::istream& i)
@@ -2128,7 +2128,11 @@ class input_stream_adapter : public input_adapter_protocol
     // end up as the same value, eg. 0xFFFFFFFF.
     std::char_traits<char>::int_type get_character() override
     {
-        return sb.sbumpc();
+        auto res = sb.sbumpc();
+        // set eof manually, as we don't use the istream interface.
+        if (res == EOF)
+            is.clear(is.rdstate() | std::ios::eofbit);
+        return res;
     }
 
   private:

test/src/unit-regression.cpp

@@ -1708,3 +1708,16 @@ TEST_CASE("regression tests")
         CHECK(expected == data);
     }
 }
+
+TEST_CASE("regression tests, exceptions dependent", "[!throws]")
+{
+    SECTION("issue #1340 - eof not set on exhausted input stream")
+    {
+        std::stringstream s("{}{}");
+        json j;
+        s >> j;
+        s >> j;
+        CHECK_THROWS_AS(s >> j, json::parse_error const&);
+        CHECK(s.eof());
+    }
+}