Fix kedro viz --load-file to run from any directory without requiring a Kedro project

docs/source/cli-docs.md

@@ -44,10 +44,10 @@
   - Whether to open the Kedro Viz interface in the default browser. The browser will open if the host is `localhost`. Defaults to `True`.
 
 - `--load-file <path>`
-  - Path to load Kedro Viz data from a directory. If provided, Kedro Viz will load the visualisation data from this path instead of generating it from the pipeline.
+  - Path to load Kedro Viz data from a [directory](https://docs.kedro.org/projects/kedro-viz/en/latest/cli-docs.html#kedro-viz-directory-structure-when-you-save-it-as-a-file). If provided, Kedro Viz will load the visualisation data from this path instead of generating it from the pipeline
 
 - `--save-file <path>`
-  - Path to save Kedro Viz data to a directory. If provided, the visualisation data will be saved to this path for later use.
+  - Path to save Kedro Viz data to a [directory](https://docs.kedro.org/projects/kedro-viz/en/latest/cli-docs.html#kedro-viz-directory-structure-when-you-save-it-as-a-file). If provided, the visualisation data will be saved to this path for later use.
 
 - `--pipeline, -p <pipeline>`
   - Name of the registered pipeline to visualise. If not set, the default pipeline is visualised.
@@ -162,4 +162,23 @@
 ```
 
 
+### Kedro-viz directory structure when you save it as a file 
+
+When you use the `--save-file` option, Kedro Viz generates a directory structure to save the visualization data. This directory can later be used with the `--load-file`  to reload the visualization.
+
+The generated directory structure looks like this:
+
+```bash
+api/
+├── main       # Main file containing pipeline structure
+├── nodes/
+│   ├── node1           # JSON files for individual nodes
+│   ├── node2
+│   └── ...
+├── pipelines/
+│   ├── pipeline1      # JSON files for individual pipelines
+│   ├── pipeline2
+│   └── ...
+```
+
 

docs/source/kedro-viz_visualisation.md

@@ -279,8 +279,8 @@ The `%run_viz` command supports various optional arguments found in `kedro viz r
 
 * `--host=<host>`: Specify the server host.
 * `--port=<port>`: Set the server port.
-* `--load-file=<file>`: Load a specific pipeline visualisation file.
-* `--save-file=<file>`: Save the current pipeline visualisation to a file.
+* `--load-file=<file>`: Load a specific pipeline visualisation from a [directory](https://docs.kedro.org/projects/kedro-viz/en/latest/cli-docs.html#kedro-viz-directory-structure-when-you-save-it-as-a-file).
+* `--save-file=<file>`: Save the current pipeline visualisation to a [directory](https://docs.kedro.org/projects/kedro-viz/en/latest/cli-docs.html#kedro-viz-directory-structure-when-you-save-it-as-a-file).
 * `--pipeline=<name>`: Visualise a specific pipeline.
 * `--env=<name>`: Set the environment for the visualisation.
 * `--autoreload`: Enable automatic reloading of the visualisation when source code changes.

package/kedro_viz/launchers/cli/run.py

@@ -123,16 +123,21 @@ def run(
     )
     from kedro_viz.server import run_server
 
-    kedro_project_path = _find_kedro_project(Path.cwd())
-
-    if kedro_project_path is None:
-        display_cli_message(
-            "ERROR: Failed to start Kedro-Viz : "
-            "Could not find the project configuration "
-            f"file '{_PYPROJECT}' at '{Path.cwd()}'. ",
-            "red",
-        )
-        return
+    kedro_project_path = None
+
+    if load_file:
+        if not Path(load_file).exists():
+            raise ValueError(f"The provided filepath '{load_file}' does not exist.")
+    else:
+        kedro_project_path = _find_kedro_project(Path.cwd())
+        if kedro_project_path is None:
+            display_cli_message(
+                "ERROR: Failed to start Kedro-Viz : "
+                "Could not find the project configuration "
+                f"file '{_PYPROJECT}' at '{Path.cwd()}'. ",
+                "red",
+            )
+            return
 
     installed_version = parse(__version__)
     latest_version = get_latest_version()

package/kedro_viz/server.py

@@ -132,9 +132,6 @@ def run_server(
 
         app = apps.create_api_app_from_project(path, autoreload)
     else:
-        if not Path(load_file).exists():
-            raise ValueError(f"The provided filepath '{load_file}' does not exist.")
-
         app = apps.create_api_app_from_file(f"{path}/{load_file}/api")
 
     uvicorn.run(app, host=host, port=port, log_config=None)

package/tests/test_launchers/test_cli/test_run.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 from unittest.mock import call
 
 import pytest
@@ -411,3 +412,23 @@ def test_find_available_port_with_occupied_ports(self, mocker):
         assert (
             available_port == 4143
         ), "Expected port 4143 to be returned as the available port"
+
+
+def test_invalid_load_file_directory(mocker):
+    """
+    Test that Kedro-Viz raises a ValueError when an invalid filepath
+    is provided to the `--load-file` argument.
+    """
+    runner = CliRunner()
+
+    # Mock the existence of the file path to always return False (invalid path)
+    mocker.patch.object(Path, "exists", return_value=False)
+
+    # Invoke the CLI with an invalid `--load-file` path
+    result = runner.invoke(
+        main.viz_cli, ["viz", "run", "--load-file", "nonexistent_path.json"]
+    )
+
+    assert "The provided filepath 'nonexistent_path.json' does not exist." == str(
+        result.exception
+    )

package/tests/test_server.py

@@ -121,32 +121,15 @@ def test_specific_pipeline(
             {"data_science": example_pipelines["data_science"]}
         )
 
-    @pytest.mark.parametrize(
-        "file_path, expected_exception",
-        [
-            ("test.json", ValueError),  # File does not exist, expect ValueError
-            ("test.json", None),  # File exists, expect no ValueError
-        ],
-    )
-    def test_load_file(
-        self, file_path, expected_exception, patched_create_api_app_from_file, tmp_path
-    ):
-        if expected_exception is not None:
-            with pytest.raises(expected_exception) as exc_info:
-                run_server(load_file=file_path)
-
-            # Check if the error message contains the expected message
-            assert "The provided filepath" in str(exc_info.value)
-            assert "does not exist." in str(exc_info.value)
-        else:
-            json_file_path = tmp_path / file_path
-
-            # File exists, no exception expected
-            with json_file_path.open("w") as file:
-                json.dump({"name": "John", "age": 30}, file)
-
-            run_server(load_file=json_file_path)
-            patched_create_api_app_from_file.assert_called_once()
+    def test_load_file(self, patched_create_api_app_from_file, tmp_path):
+        file_path = "test.json"
+        json_file_path = tmp_path / file_path
+
+        with json_file_path.open("w") as file:
+            json.dump({"name": "John", "age": 30}, file)
+
+        run_server(load_file=json_file_path)
+        patched_create_api_app_from_file.assert_called_once()
 
     def test_save_file(self, tmp_path, mocker):
         mock_filesystem = mocker.patch("fsspec.filesystem")