Kedro CLI startup time made shorter (#1196)

- server.py: Moved `DEFAULT_HOST` and `DEFAULT_PORT` to `constants.py`
- launchers/cli.py: Moved `from kedro_viz.server ...` statement to
  viz function
- modified tests so they follow new code structure

Signed-off-by: Konrad Sikorski <znfgnu@gmail.com>

Signed-off-by: Konrad Sikorski <znfgnu@gmail.com>

RELEASE.md

@@ -12,6 +12,7 @@ Please follow the established format:
 
 - Allow users to hide modular pipelines on the flowchart. (#1046)
 - Create URL parameters for each element/section in the flowchart. (#1138)
+- Improve CLI loading time. (#1196)
 
 ## Bug fixes and other changes
 

package/kedro_viz/constants.py

@@ -5,3 +5,6 @@
 DEFAULT_REGISTERED_PIPELINE_ID = "__default__"
 KEDRO_VERSION = VersionInfo.parse(kedro.__version__)
 ROOT_MODULAR_PIPELINE_ID = "__root__"
+
+DEFAULT_HOST = "127.0.0.1"
+DEFAULT_PORT = 4141

package/kedro_viz/launchers/cli.py

@@ -11,8 +11,8 @@
 from watchgod import RegExpWatcher, run_process
 
 from kedro_viz import __version__
+from kedro_viz.constants import DEFAULT_HOST, DEFAULT_PORT
 from kedro_viz.integrations.pypi import get_latest_version, is_running_outdated_version
-from kedro_viz.server import DEFAULT_HOST, DEFAULT_PORT, is_localhost, run_server
 
 
 @click.group(name="Kedro-Viz")
@@ -80,8 +80,11 @@ def commands():  # pylint: disable=missing-function-docstring
     help=PARAMS_ARG_HELP,
     callback=_split_params,
 )
+# pylint: disable=import-outside-toplevel, too-many-locals
 def viz(host, port, browser, load_file, save_file, pipeline, env, autoreload, params):
     """Visualise a Kedro pipeline using Kedro viz."""
+    from kedro_viz.server import is_localhost, run_server
+
     installed_version = VersionInfo.parse(__version__)
     latest_version = get_latest_version()
 

package/kedro_viz/server.py

@@ -11,13 +11,12 @@
 
 from kedro_viz.api import apps
 from kedro_viz.api.rest.responses import EnhancedORJSONResponse, get_default_response
+from kedro_viz.constants import DEFAULT_HOST, DEFAULT_PORT
 from kedro_viz.data_access import DataAccessManager, data_access_manager
 from kedro_viz.database import create_db_engine
 from kedro_viz.integrations.kedro import data_loader as kedro_data_loader
 from kedro_viz.models.experiment_tracking import Base
 
-DEFAULT_HOST = "127.0.0.1"
-DEFAULT_PORT = 4141
 DEV_PORT = 4142
 
 

package/tests/test_launchers/test_cli.py

@@ -6,6 +6,7 @@
 
 from kedro_viz import __version__
 from kedro_viz.launchers import cli
+from kedro_viz.server import run_server
 
 
 @pytest.mark.parametrize(
@@ -57,7 +58,7 @@
     ],
 )
 def test_kedro_viz_command_run_server(command_options, run_server_args, mocker):
-    run_server = mocker.patch("kedro_viz.launchers.cli.run_server")
+    run_server = mocker.patch("kedro_viz.server.run_server")
     runner = CliRunner()
     with runner.isolated_filesystem():
         runner.invoke(cli.commands, command_options)
@@ -74,7 +75,7 @@ def test_kedro_viz_command_should_log_outdated_version(mocker, mock_http_respons
     )
     mock_click_echo = mocker.patch("click.echo")
 
-    mocker.patch("kedro_viz.launchers.cli.run_server")
+    mocker.patch("kedro_viz.server.run_server")
     runner = CliRunner()
     with runner.isolated_filesystem():
         runner.invoke(cli.commands, ["viz"])
@@ -96,7 +97,7 @@ def test_kedro_viz_command_should_not_log_latest_version(mocker, mock_http_respo
     )
     mock_click_echo = mocker.patch("click.echo")
 
-    mocker.patch("kedro_viz.launchers.cli.run_server")
+    mocker.patch("kedro_viz.server.run_server")
     runner = CliRunner()
     with runner.isolated_filesystem():
         runner.invoke(cli.commands, ["viz"])
@@ -109,7 +110,7 @@ def test_kedro_viz_command_should_not_log_if_pypi_is_down(mocker, mock_http_resp
     requests_get.side_effect = requests.exceptions.RequestException("PyPI is down")
     mock_click_echo = mocker.patch("click.echo")
 
-    mocker.patch("kedro_viz.launchers.cli.run_server")
+    mocker.patch("kedro_viz.server.run_server")
     runner = CliRunner()
     with runner.isolated_filesystem():
         runner.invoke(cli.commands, ["viz"])
@@ -128,7 +129,7 @@ def test_kedro_viz_command_with_autoreload(mocker):
 
     run_process.assert_called_once_with(
         path=mock_project_path,
-        target=cli.run_server,
+        target=run_server,
         kwargs={
             "host": "127.0.0.1",
             "port": 4141,