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Artificial-Sweetener-Simple…/simple_syrup/runtime/checkpoint_loader.py
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# SimpleSyrup - workflow-focused ComfyUI extensions for image generation
# Copyright (C) 2026 Artificial Sweetener and contributors
# SPDX-License-Identifier: AGPL-3.0-or-later
"""Load checkpoints with optional external VAE replacement."""
from __future__ import annotations
import importlib
from collections.abc import Iterable
from types import ModuleType
from typing import Any, Protocol, cast
from .clip_patcher_mutations import ClipLayerMutation
from .patcher_lifecycle import PATCHER_LIFECYCLE, ComfyPatcherLifecycle
from .vae_loader import VaeLoaderService
USE_CHECKPOINT_VAE_CHOICE = "Use Checkpoint VAE"
CLIP_SKIP_DEFAULT = False
CLIP_SKIP_LAYER = -2
class CheckpointLoaderService:
"""Load a checkpoint and optionally adjust its CLIP and VAE outputs."""
def __init__(
self,
folder_paths_module: ModuleType | None = None,
vae_loader: VaeLoaderBoundary | None = None,
patcher_lifecycle: ComfyPatcherLifecycle | None = None,
) -> None:
"""Create a checkpoint loader with injectable runtime boundaries."""
self._folder_paths_module = folder_paths_module
self._vae_loader = vae_loader or VaeLoaderService(folder_paths_module)
self._patcher_lifecycle = patcher_lifecycle or PATCHER_LIFECYCLE
def load_checkpoint(
self,
ckpt_name: str,
vae_name: str,
clip_skip: bool = CLIP_SKIP_DEFAULT,
) -> tuple[object, object, object]:
"""Return MODEL, CLIP, and selected VAE objects."""
_validate_clip_skip(clip_skip)
folder_paths = self._folder_paths()
ckpt_path = folder_paths.get_full_path_or_raise("checkpoints", ckpt_name)
comfy_sd = _comfy_sd()
loaded = tuple(
cast(
Iterable[object],
comfy_sd.load_checkpoint_guess_config(
ckpt_path,
output_vae=True,
output_clip=True,
embedding_directory=folder_paths.get_folder_paths("embeddings"),
),
)
)
model = loaded[0]
clip = loaded[1]
checkpoint_vae = loaded[2]
selected_clip = self._selected_clip(clip, clip_skip)
if vae_name == USE_CHECKPOINT_VAE_CHOICE:
selected_vae = checkpoint_vae
else:
selected_vae = self._vae_loader.load_vae(vae_name)
return (
model,
selected_clip,
self._patcher_lifecycle.preserve_vae(
selected_vae,
operation="SimpleSyrup checkpoint loading",
),
)
def _selected_clip(self, clip: object, clip_skip: bool) -> object:
"""Return the loaded CLIP or a lifecycle-owned clip-skip derivation."""
if not clip_skip:
return clip
return self._patcher_lifecycle.derive_clip(
clip,
(ClipLayerMutation(CLIP_SKIP_LAYER),),
operation="SimpleSyrup checkpoint clip skip",
)
def _folder_paths(self) -> ModuleType:
"""Return the ComfyUI folder_paths module."""
if self._folder_paths_module is not None:
return self._folder_paths_module
module: Any = importlib.import_module("folder_paths")
if not isinstance(module, ModuleType):
raise TypeError("folder_paths import did not return a module.")
self._folder_paths_module = module
return module
class VaeLoaderBoundary(Protocol):
"""VAE loader interface required by the checkpoint loader."""
def load_vae(self, vae_name: str) -> object:
"""Load the named external VAE."""
def _validate_clip_skip(clip_skip: object) -> None:
"""Reject non-boolean clip-skip selections from runtime callers."""
if not isinstance(clip_skip, bool):
raise TypeError("clip_skip must be a boolean.")
def _comfy_sd() -> Any:
"""Import ComfyUI's stable diffusion loading module lazily."""
return importlib.import_module("comfy.sd")