feat(nodes): simple custom nodes

Custom nodes may be places in `$INVOKEAI_ROOT/nodes/` (configurable with `custom_nodes_dir` option).

On app startup, an `__init__.py` is copied into the custom nodes dir, which recursively loads all python files in the directory as modules (files starting with `_` are ignored). The custom nodes dir is now a python module itself.

When we `from invocations import *` to load init all invocations, we load the custom nodes dir, registering all custom nodes.

invokeai/app/invocations/__init__.py

@@ -1,8 +1,25 @@
-import os
+import shutil
+import sys
+from importlib.util import module_from_spec, spec_from_file_location
+from pathlib import Path
 
-__all__ = []
+from invokeai.app.services.config.config_default import InvokeAIAppConfig
 
-dirname = os.path.dirname(os.path.abspath(__file__))
-for f in os.listdir(dirname):
-    if f != "__init__.py" and os.path.isfile("%s/%s" % (dirname, f)) and f[-3:] == ".py":
-        __all__.append(f[:-3])
+custom_nodes_path = Path(InvokeAIAppConfig.get_config().custom_nodes_path.absolute())
+custom_nodes_path.mkdir(parents=True, exist_ok=True)
+custom_nodes_init_path = str(custom_nodes_path / "__init__.py")
+
+# copy our custom nodes __init__.py to the custom nodes directory
+shutil.copy(Path(__file__).parent / "_custom_nodes_init.py", custom_nodes_init_path)
+
+# Import custom nodes, see https://docs.python.org/3/library/importlib.html#importing-programmatically
+spec = spec_from_file_location("custom_nodes", custom_nodes_init_path)
+if spec is None or spec.loader is None:
+    raise RuntimeError(f"Could not load custom nodes from {custom_nodes_init_path}")
+module = module_from_spec(spec)
+sys.modules[spec.name] = module
+spec.loader.exec_module(module)
+
+# add core nodes to __all__
+python_files = filter(lambda f: not f.name.startswith("_"), Path(__file__).parent.rglob("*.py"))
+__all__ = list(f.stem for f in python_files)  # type: ignore

invokeai/app/invocations/_custom_nodes_init.py

@@ -0,0 +1,37 @@
+"""
+InvokeAI custom nodes initialization
+
+This file is responsible for loading all custom nodes from this directory.
+
+All python files are loaded on app startup. Custom nodes will be initialized and available for use
+in workflows.
+
+The app must be restarted for changes to be picked up.
+
+This file is overwritten on launch. Do not edit this file directly.
+"""
+import sys
+from importlib import import_module
+from importlib.util import module_from_spec, spec_from_file_location
+from pathlib import Path
+
+from invokeai.backend.util.logging import InvokeAILogger
+
+logger = InvokeAILogger.get_logger()
+count = 0
+for f in Path(__file__).parent.rglob("*.py"):
+    module_name = f.stem
+    if (not module_name.startswith("_")) and (module_name not in globals()):
+        spec = spec_from_file_location(module_name, f.absolute())
+        if spec is None or spec.loader is None:
+            logger.warn(f"Could not load {f}")
+            continue
+        module = module_from_spec(spec)
+        sys.modules[spec.name] = module
+        spec.loader.exec_module(module)
+        count += 1
+    del f, module_name
+
+logger.info(f"Loaded {count} modules from {Path(__file__).parent}")
+
+del import_module, Path

invokeai/app/services/config/config_default.py

@@ -243,6 +243,7 @@ class InvokeAIAppConfig(InvokeAISettings):
     db_dir              : Optional[Path] = Field(default=Path('databases'), description='Path to InvokeAI databases directory', json_schema_extra=Categories.Paths)
     outdir              : Optional[Path] = Field(default=Path('outputs'), description='Default folder for output images', json_schema_extra=Categories.Paths)
     use_memory_db       : bool = Field(default=False, description='Use in-memory database for storing image metadata', json_schema_extra=Categories.Paths)
+    custom_nodes_dir    : Path = Field(default=Path('nodes'), description='Path to directory for custom nodes', json_schema_extra=Categories.Paths)
     from_file           : Optional[Path] = Field(default=None, description='Take command input from the indicated file (command-line client only)', json_schema_extra=Categories.Paths)
 
     # LOGGING
@@ -410,6 +411,13 @@ class InvokeAIAppConfig(InvokeAISettings):
         """
         return self._resolve(self.models_dir)
 
+    @property
+    def custom_nodes_path(self) -> Path:
+        """
+        Path to the custom nodes directory
+        """
+        return self._resolve(self.custom_nodes_dir)
+
     # the following methods support legacy calls leftover from the Globals era
     @property
     def full_precision(self) -> bool: