Feature: Blender hook to execute python scripts at launch

openpype/hosts/blender/hooks/pre_add_run_python_script_arg.py

@@ -0,0 +1,61 @@
+from pathlib import Path
+
+from openpype.lib import PreLaunchHook
+from openpype.settings.lib import get_project_settings
+
+
+class AddPythonScriptToLaunchArgs(PreLaunchHook):
+    """Add python script to be executed before Blender launch."""
+
+    # Append after file argument
+    order = 15
+    app_groups = [
+        "blender",
+    ]
+
+    def execute(self):
+        # Check enabled in settings
+        project_name = self.data["project_name"]
+        project_settings = get_project_settings(project_name)
+        host_name = self.application.host_name
+        host_settings = project_settings.get(host_name)
+        if not host_settings:
+            self.log.info(f"""Host "{host_name}" doesn\'t have settings""")
+            return None
+
+        # Add path to workfile to arguments
+        for python_script_path in self.launch_context.data.get(
+            "python_scripts", []
+        ):
+            self.log.info(
+                f"Adding python script {python_script_path} to launch"
+            )
+            # Test script path exists
+            if not Path(python_script_path).exists():
+                raise ValueError(
+                    f"Python script {python_script_path} doesn't exist."
+                )
+
+            if "--" in self.launch_context.launch_args:
+                # Insert before separator
+                separator_index = self.launch_context.launch_args.index("--")
+                self.launch_context.launch_args.insert(
+                    separator_index,
+                    "-P",
+                )
+                self.launch_context.launch_args.insert(
+                    separator_index + 1,
+                    Path(python_script_path).as_posix(),
+                )
+            else:
+                self.launch_context.launch_args.extend(
+                    ["-P", Path(python_script_path).as_posix()]
+                )
+
+        # Ensure separator
+        if "--" not in self.launch_context.launch_args:
+            self.launch_context.launch_args.append("--")
+
+        self.launch_context.launch_args.extend(
+            [*self.launch_context.data.get("script_args", [])]
+        )

website/docs/dev_blender.md

@@ -0,0 +1,61 @@
+---
+id: dev_blender
+title: Blender integration
+sidebar_label: Blender integration
+toc_max_heading_level: 4
+---
+
+## Run python script at launch
+In case you need to execute a python script when Blender is started (aka [`-P`](https://docs.blender.org/manual/en/latest/advanced/command_line/arguments.html#python-options)), for example to programmatically modify a blender file for conformation, you can create an OpenPype hook as follows:
+
+```python
+from openpype.hosts.blender.hooks.pre_add_run_python_script_arg import AddPythonScriptToLaunchArgs
+from openpype.lib import PreLaunchHook
+
+
+class MyHook(PreLaunchHook):
+    """Add python script to be executed before Blender launch."""
+
+    order = AddPythonScriptToLaunchArgs.order - 1
+    app_groups = [
+        "blender",
+    ]
+
+    def execute(self):
+        self.launch_context.data.setdefault("python_scripts", []).append(
+            "/path/to/my_script.py"
+        )
+```
+
+You can write a bare python script, as you could run into the [Text Editor](https://docs.blender.org/manual/en/latest/editors/text_editor.html).
+
+### Python script with arguments
+#### Adding arguments
+In case you need to pass arguments to your script, you can append them to `self.launch_context.data["script_args"]`:
+
+```python
+self.launch_context.data.setdefault("script_args", []).append(
+        "--my-arg",
+        "value",
+    )
+```
+
+#### Parsing arguments
+You can parse arguments in your script using [argparse](https://docs.python.org/3/library/argparse.html) as follows:
+
+```python
+import argparse
+
+parser = argparse.ArgumentParser(
+    description="Parsing arguments for my_script.py"
+)
+parser.add_argument(
+    "--my-arg",
+    nargs="?",
+    help="My argument",
+)
+args, unknown = arg_parser.parse_known_args(
+    sys.argv[sys.argv.index("--") + 1 :]
+)
+print(args.my_arg)
+```

website/sidebars.js

@@ -179,6 +179,7 @@ module.exports = {
             ]
         },
         "dev_deadline",
+        "dev_blender",
         "dev_colorspace"
     ]
 };