[cli] Ensure load-scenes can only be specified once

Disallow combining `load-scenes` with detectors to avoid confusion. #347

scenedetect/_cli/context.py

@@ -418,9 +418,8 @@ def get_detect_threshold_params(
                 else:
                     min_scene_len = self.config.get_value("detect-threshold", "min-scene-len")
             min_scene_len = parse_timecode(min_scene_len, self.video_stream.frame_rate).frame_num
-
+        # TODO(v1.0): add_last_scene cannot be disabled right now.
         return {
-                                                                                                # TODO(v1.0): add_last_scene cannot be disabled right now.
             'add_final_scene':
                 add_last_scene or self.config.get_value("detect-threshold", "add-last-scene"),
             'fade_bias':
@@ -434,6 +433,10 @@ def get_detect_threshold_params(
     def handle_load_scenes(self, input: AnyStr, start_col_name: Optional[str]):
         """Handle `load-scenes` command options."""
         self._ensure_input_open()
+        if self.scene_manager._detector_list:
+            raise click.ClickException(
+                "The load-scenes command cannot be used with other detectors, and may only be "
+                "specified once.")
         start_col_name = self.config.get_value("load-scenes", "start-col-name", start_col_name)
         self.add_detector(
             SceneLoader(
@@ -735,12 +738,7 @@ def _initialize_logging(
     def add_detector(self, detector):
         """ Add Detector: Adds a detection algorithm to the CliContext's SceneManager. """
         self._ensure_input_open()
-        try:
-            self.scene_manager.add_detector(detector)
-        except scenedetect.stats_manager.FrameMetricRegistered as ex:
-            raise click.BadParameter(
-                message='Cannot specify detection algorithm twice.',
-                param_hint=detector.cli_name) from ex
+        self.scene_manager.add_detector(detector)
 
     def _ensure_input_open(self) -> None:
         """Ensure self.video_stream was initialized (i.e. -i/--input was specified),

tests/test_cli.py

@@ -381,7 +381,17 @@ def test_cli_load_scenes():
     """Ensure we can load scenes both with and without the cut row."""
     assert invoke_scenedetect('-i {VIDEO} time {TIME} {DETECTOR} list-scenes') == 0
     assert invoke_scenedetect('-i {VIDEO} time {TIME} load-scenes -i {VIDEO_NAME}-Scenes.csv') == 0
+    # Specifying a detector with load-scenes should be disallowed.
+    assert invoke_scenedetect(
+        '-i {VIDEO} time {TIME} {DETECTOR} load-scenes -i {VIDEO_NAME}-Scenes.csv')
+    # Specifying load-scenes several times should be disallowed.
+    assert invoke_scenedetect(
+        '-i {VIDEO} time {TIME} load-scenes -i {VIDEO_NAME}-Scenes.csv load-scenes -i {VIDEO_NAME}-Scenes.csv'
+    )
+    # If `-s`/`--skip-cuts` is specified, the resulting scene list should still be compatible with
+    # the `load-scenes` command.
     assert invoke_scenedetect('-i {VIDEO} time {TIME} {DETECTOR} list-scenes -s') == 0
+    assert invoke_scenedetect('-i {VIDEO} time {TIME} load-scenes -i {VIDEO_NAME}-Scenes.csv') == 0
 
 
 def test_cli_load_scenes_with_time_frames():

website/pages/changelog.md

@@ -23,6 +23,7 @@ This release focuses on bugfixes and quality of life improvements. This has help
       - Valid values: `frames`, `timecode`, `seconds`
  - [general] Increase progress bar indent to improve visibility and visual alignment
  - [improvement] The `s` suffix for setting timecode values in seconds is no longer required (values without decimal places are still interpreted as frame numbers)
+ - [general] The `load-scenes` command may only be specified once, and is now disallowed with other `detect-*` commands [#347](https://github.com/Breakthrough/PySceneDetect/issues/347)
 
 **API Changes:**