(KED-1516) Stop kedro-viz from swallowing stacktraces

RELEASE.md

@@ -19,7 +19,8 @@ Please follow the established format:
 - Drop support for Python 3.5 (#138)
 - Add logger configuration when loading pipeline from JSON (#133)
 - Move visibleNav/navWidth calculations into Redux store (#124)
-- Web browser will only be opened if the host corresponds to the localhost 
+- Web browser will only be opened if the host corresponds to the localhost (#136)
+- Print the stack trace when encountering a generic exception (#142)
 
 ## Thanks for supporting contributions
 

package/kedro_viz/server.py

@@ -33,6 +33,7 @@
 import logging
 import multiprocessing
 import socket
+import traceback
 import webbrowser
 from collections import defaultdict
 from contextlib import closing
@@ -305,6 +306,7 @@ def viz(host, port, browser, load_file, save_file, pipeline, env):
     except KedroCliError:
         raise
     except Exception as ex:
+        traceback.print_exc()
         raise KedroCliError(str(ex))
 
 

package/tests/test_server.py

@@ -202,7 +202,9 @@ def test_no_browser_if_not_localhost(cli_runner):
     """Check that call to open browser is not performed when host
     is not the local host.
     """
-    result = cli_runner.invoke(server.commands, ["viz", "--browser", "--host", "123.1.2.3"])
+    result = cli_runner.invoke(
+        server.commands, ["viz", "--browser", "--host", "123.1.2.3"]
+    )
     assert result.exit_code == 0, result.output
     assert not server.webbrowser.open_new.called
     result = cli_runner.invoke(server.commands, ["viz", "--host", "123.1.2.3"])
@@ -385,6 +387,16 @@ def test_viz_kedro14_invalid(mocker, cli_runner):
     assert "Could not find a Kedro project root." in result.output
 
 
+def test_viz_stacktrace(mocker, cli_runner):
+    """Test that in the case of a generic exception,
+    the stacktrace is printer."""
+    mocker.patch("kedro_viz.server._call_viz", side_effect=ValueError)
+    result = cli_runner.invoke(server.commands, "viz")
+
+    assert "Traceback (most recent call last):" in result.output
+    assert "ValueError" in result.output
+
+
 @pytest.fixture(autouse=True)
 def clean_up():
     # pylint: disable=protected-access