connect: fix crash due to an empty response

We did not check the response size, which may lead to a crash
due to an index out of range.

Closes #964

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Command `\set delimiter [marker]` works correctly and don't hangs `tt` console.
 
 - `tt log -f` crash on removing log directory.
+- `tt connect` crash due to an empty response.
 
 ### Changed
 

cli/connect/connect.go

@@ -122,13 +122,20 @@ func Eval(connectCtx ConnectCtx, connOpts connector.ConnectOpts, args []string)
 	// Check that the result is encoded in YAML and convert it to bytes,
 	// since the ""gopkg.in/yaml.v2" library handles YAML as an array
 	// of bytes.
-	resYAML := []byte((response[0]).(string))
+	var resYAML string
+	if len(response) > 0 {
+		if str, ok := response[0].(string); ok {
+			resYAML = str
+		} else {
+			return nil, fmt.Errorf("unexpected response type: %T", response[0])
+		}
+	}
 	var checkMock interface{}
-	if err = yaml.Unmarshal(resYAML, &checkMock); err != nil {
+	if err = yaml.Unmarshal([]byte(resYAML), &checkMock); err != nil {
 		return nil, err
 	}
 
-	return resYAML, nil
+	return []byte(resYAML), nil
 }
 
 // runConsole run a new console.

test/integration/connect/test_connect.py

@@ -66,14 +66,19 @@ def stop_app(tt_cmd, tmpdir, app_name):
 def try_execute_on_instance(tt_cmd, tmpdir, instance,
                             file_path=None,
                             stdin=None,
+                            stdin_as_file=False,
                             env=None,
                             opts=None,
                             args=None):
     connect_cmd = [tt_cmd, "connect", instance]
+
     if file_path is not None:
         connect_cmd.append("-f")
         connect_cmd.append(file_path)
 
+    if stdin_as_file:
+        connect_cmd.append("-f-")
+
     if opts is not None:
         for k, v in opts.items():
             connect_cmd.append(k)
@@ -138,6 +143,12 @@ def get_version(tt_cmd, tmpdir):
     return False, 0, 0, 0
 
 
+def is_quit_supported(tt_cmd, tmpdir):
+    ok, major, minor, patch = get_version(tt_cmd, tmpdir)
+    assert ok
+    return major >= 2
+
+
 def is_language_supported(tt_cmd, tmpdir):
     ok, major, minor, patch = get_version(tt_cmd, tmpdir)
     assert ok
@@ -169,6 +180,11 @@ def is_tarantool_major_one():
     return False
 
 
+def skip_if_quit_unsupported(tt_cmd, tmpdir):
+    if not is_quit_supported(tt_cmd, tmpdir):
+        pytest.skip("\\q is unsupported")
+
+
 def skip_if_language_unsupported(tt_cmd, tmpdir, test_app):
     if not is_language_supported(tt_cmd, tmpdir):
         stop_app(tt_cmd, tmpdir, test_app)
@@ -359,6 +375,38 @@ def test_connect_and_get_commands_errors(tt_cmd, tmpdir_with_cfg):
         stop_app(tt_cmd, tmpdir, "test_app")
 
 
+def test_connect_and_execute_quit(tt_cmd, tmpdir_with_cfg):
+    tmpdir = tmpdir_with_cfg
+    empty_file = "empty.lua"
+
+    skip_if_quit_unsupported(tt_cmd, tmpdir)
+
+    # The test application file.
+    test_app_path = os.path.join(os.path.dirname(__file__), "test_single_app", "test_app.lua")
+    # The test file.
+    empty_file_path = os.path.join(os.path.dirname(__file__), "test_file", empty_file)
+    # Copy test data into temporary directory.
+    copy_data(tmpdir, [test_app_path, empty_file_path])
+
+    # Start an instance.
+    start_app(tt_cmd, tmpdir, "test_app")
+
+    # Check for start.
+    file = wait_file(os.path.join(tmpdir, "test_app", run_path, "test_app"),
+                     control_socket, [])
+    assert file != ""
+
+    try:
+        ret, output = try_execute_on_instance(tt_cmd, tmpdir, "test_app",
+                                              stdin="\\q",
+                                              stdin_as_file=True)
+        assert ret
+
+        assert output == "\n"
+    finally:
+        stop_app(tt_cmd, tmpdir, "test_app")
+
+
 def test_connect_to_localhost_app(tt_cmd, tmpdir_with_cfg):
     tmpdir = tmpdir_with_cfg
     empty_file = "empty.lua"