Raise error when modules_to_save is specified and multiple adapters…

… are being unloaded (huggingface#1137)

* handle `modules_to_save` when unloading

* address comments

* Apply suggestions from code review

Co-authored-by: Benjamin Bossan <[email protected]>

* quality

---------

Co-authored-by: Benjamin Bossan <[email protected]>

src/peft/tuners/ia3/model.py

@@ -313,6 +313,7 @@ def _unload_and_optionally_merge(
         if getattr(self.model, "is_loaded_in_4bit", False):
             raise ValueError("Cannot merge ia3 layers when the model is loaded in 4-bit mode")
 
+        self._unloading_checks(adapter_names)
         key_list = [key for key, _ in self.model.named_modules() if self.prefix not in key]
         for key in key_list:
             try:

src/peft/tuners/lora/model.py

@@ -426,6 +426,7 @@ def _unload_and_optionally_merge(
             if getattr(self.model, "quantization_method", None) == "gptq":
                 raise ValueError("Cannot merge LORA layers when the model is gptq quantized")
 
+        self._unloading_checks(adapter_names)
         key_list = [key for key, _ in self.model.named_modules() if self.prefix not in key]
         desc = "Unloading " + ("and merging " if merge else "") + "model"
         for key in tqdm(key_list, disable=not progressbar, desc=desc):

src/peft/tuners/lycoris_utils.py

@@ -37,6 +37,7 @@ class LycorisConfig(PeftConfig):
     r"""
     A base config for LyCORIS like adapters
     """
+
     rank_pattern: Optional[dict] = field(
         default_factory=dict,
         metadata={
@@ -61,6 +62,7 @@ class LycorisLayer(BaseTunerLayer):
     r"""
     A base layer for LyCORIS like adapters
     """
+
     # adapter_layer_names needs to be defined on the child class
     other_param_names = ("r", "alpha", "scaling", "rank_dropout", "module_dropout")
 
@@ -319,6 +321,7 @@ def _unload_and_optionally_merge(
             if getattr(self.model, "quantization_method", None) == "gptq":
                 raise ValueError("Cannot merge LOHA layers when the model is gptq quantized")
 
+        self._unloading_checks(adapter_names)
         key_list = [key for key, _ in self.model.named_modules() if self.prefix not in key]
         desc = "Unloading " + ("and merging " if merge else "") + "model"
         for key in tqdm(key_list, disable=not progressbar, desc=desc):

src/peft/tuners/tuners_utils.py

@@ -18,7 +18,7 @@
 import re
 import warnings
 from abc import ABC, abstractmethod
-from typing import Any, Optional, Union
+from typing import Any, List, Optional, Union
 
 import torch
 from torch import nn
@@ -299,6 +299,14 @@ def unmerge_adapter(self):
             if isinstance(module, BaseTunerLayer):
                 module.unmerge()
 
+    def _unloading_checks(self, adapter_names: Optional[List[str]]):
+        adapters_to_consider = adapter_names or self.active_adapters
+        is_modules_to_save_available = any(
+            self.peft_config[adapter].modules_to_save for adapter in adapters_to_consider
+        )
+        if is_modules_to_save_available and len(adapters_to_consider) > 1:
+            raise ValueError("Cannot unload multiple adapters that specify `modules_to_save`.")
+
 
 class BaseTunerLayer(ABC):
     r"""
@@ -310,6 +318,7 @@ class BaseTunerLayer(ABC):
         active_adapters (Union[List[`str`], `str`], *optional*):
             The name of the active adapter.
     """
+
     active_adapter = None
 
     # All names of layers that may contain adapter (trainable) weights