Implement simple continuation.

Fixes #1.

Author: vgvassilev

src/xinterpreter.cpp

@@ -279,9 +279,18 @@ __get_cxx_version ()
         return kernel_res;
     }
 
-    nl::json interpreter::is_complete_request_impl(const std::string& /*code*/)
+    nl::json interpreter::is_complete_request_impl(const std::string& code)
     {
-        return xeus::create_is_complete_reply("complete", "   ");
+        if (!code.empty() && code[code.size() - 1] == '\\') {
+            auto found = code.rfind('\n');
+            if (found == std::string::npos)
+                found = -1;
+            auto found1 = found++;
+            while (isspace(code[++found1])) ;
+            return xeus::create_is_complete_reply("incomplete", code.substr(found, found1-found));
+        }
+
+        return xeus::create_is_complete_reply("complete");
     }
 
     nl::json interpreter::kernel_info_request_impl()

test/test_xcpp_kernel.py

@@ -37,6 +37,32 @@ def test_codecomplete(self) -> None:
         self.assertEqual(str(reply["content"]["matches"]), "['float', 'foo']")
         self.assertEqual(reply["content"]["status"], "ok")
 
+    # Continuation
+    code_continuation_incomplete = '  int foo = 12; \\\n  float bar = 1.5f;\\'
+    code_continuation_complete =   '  int foo = 12; \\\n  float bar = 1.5f;'
+
+    def test_continuation(self) -> None:
+        if not self.code_continuation_incomplete or not self.code_continuation_complete:
+            raise SkipTest("No code continuation sample")
+
+        # Incomplete
+        self.flush_channels()
+        msg_id = self.kc.is_complete(self.code_continuation_incomplete)
+        reply = self.get_non_kernel_info_reply(timeout=1)
+        assert reply is not None
+        self.assertEqual(reply["msg_type"], "is_complete_reply")
+        self.assertEqual(str(reply["content"]["indent"]), "  ")
+        self.assertEqual(reply["content"]["status"], "incomplete")
+
+        # Complete
+        self.flush_channels()
+        msg_id = self.kc.is_complete(self.code_continuation_complete)
+        reply = self.get_non_kernel_info_reply(timeout=1)
+        assert reply is not None
+        self.assertEqual(reply["msg_type"], "is_complete_reply")
+        self.assertEqual(str(reply["content"]["indent"]), "")
+        self.assertEqual(reply["content"]["status"], "complete")
+
 
 class XCppTests(jupyter_kernel_test.KernelTests):