Allow soft dependencies in the namespace with ImportErrors at use (#7537)

* PoC on RAG

* Format class name/obj name

* Better name in message

* PoC on one TF model

* Add PyTorch and TF dummy objects + script

* Treat scikit-learn

* Bad copy pastes

* Typo

.circleci/config.yml

@@ -248,6 +248,7 @@ jobs:
             - run: isort --check-only examples templates tests src utils
             - run: flake8 examples templates tests src utils
             - run: python utils/check_copies.py
+            - run: python utils/check_dummies.py
             - run: python utils/check_repo.py
     check_repository_consistency:
         working_directory: ~/transformers

Makefile

@@ -23,6 +23,7 @@ modified_only_fixup:
 
 extra_quality_checks:
 	python utils/check_copies.py
+	python utils/check_dummies.py
 	python utils/check_repo.py
 
 # this target runs checks on all files
@@ -46,6 +47,7 @@ fixup: modified_only_fixup extra_quality_checks
 
 fix-copies:
 	python utils/check_copies.py --fix_and_overwrite
+	python utils/check_dummies.py --fix_and_overwrite
 
 # Run tests for the library
 

src/transformers/__init__.py

@@ -73,12 +73,13 @@ from .data import (
     SquadFeatures,
     SquadV1Processor,
     SquadV2Processor,
+    glue_compute_metrics,
     glue_convert_examples_to_features,
     glue_output_modes,
     glue_processors,
     glue_tasks_num_labels,
-    is_sklearn_available,
     squad_convert_examples_to_features,
+    xnli_compute_metrics,
     xnli_output_modes,
     xnli_processors,
     xnli_tasks_num_labels,
@@ -102,6 +103,7 @@ from .file_utils import (
     is_faiss_available,
     is_psutil_available,
     is_py3nvml_available,
+    is_sklearn_available,
     is_tf_available,
     is_torch_available,
     is_torch_tpu_available,
@@ -212,10 +214,6 @@ from .utils import logging
 logger = logging.get_logger(__name__)  # pylint: disable=invalid-name
 
 
-if is_sklearn_available():
-    from .data import glue_compute_metrics, xnli_compute_metrics
-
-
 # Modeling
 if is_torch_available():
     # Benchmarks
@@ -531,6 +529,8 @@ if is_torch_available():
 
     # Trainer
     from .trainer import EvalPrediction, Trainer, set_seed, torch_distributed_zero_first
+else:
+    from .utils.dummy_pt_objects import *
 
 # TensorFlow
 if is_tf_available():
@@ -753,6 +753,11 @@ if is_tf_available():
     # Trainer
     from .trainer_tf import TFTrainer
 
+else:
+    # Import the same objects as dummies to get them in the namespace.
+    # They will raise an import error if the user tries to instantiate / use them.
+    from .utils.dummy_tf_objects import *
+
 
 if not is_tf_available() and not is_torch_available():
     logger.warning(

src/transformers/data/__init__.py

@@ -2,7 +2,7 @@
 # There's no way to ignore "F401 '...' imported but unused" warnings in this
 # module, but to preserve other warnings. So, don't check this module at all.
 
-from .metrics import is_sklearn_available
+from .metrics import glue_compute_metrics, xnli_compute_metrics
 from .processors import (
     DataProcessor,
     InputExample,
@@ -21,7 +21,3 @@ from .processors import (
     xnli_processors,
     xnli_tasks_num_labels,
 )
-
-
-if is_sklearn_available():
-    from .metrics import glue_compute_metrics, xnli_compute_metrics

src/transformers/data/metrics/__init__.py

@@ -14,26 +14,22 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-try:
-    from sklearn.metrics import f1_score, matthews_corrcoef
-
-    from scipy.stats import pearsonr, spearmanr
+from ...file_utils import is_sklearn_available, requires_sklearn
 
-    _has_sklearn = True
-except (AttributeError, ImportError):
-    _has_sklearn = False
 
+if is_sklearn_available():
+    from sklearn.metrics import f1_score, matthews_corrcoef
 
-def is_sklearn_available():
-    return _has_sklearn
-
+    from scipy.stats import pearsonr, spearmanr
 
-if _has_sklearn:
 
-    def simple_accuracy(preds, labels):
+def simple_accuracy(preds, labels):
+    requires_sklearn(simple_accuracy)
     return (preds == labels).mean()
 
-    def acc_and_f1(preds, labels):
+
+def acc_and_f1(preds, labels):
+    requires_sklearn(acc_and_f1)
     acc = simple_accuracy(preds, labels)
     f1 = f1_score(y_true=labels, y_pred=preds)
     return {
@@ -42,7 +38,9 @@ if _has_sklearn:
         "acc_and_f1": (acc + f1) / 2,
     }
 
-    def pearson_and_spearman(preds, labels):
+
+def pearson_and_spearman(preds, labels):
+    requires_sklearn(pearson_and_spearman)
     pearson_corr = pearsonr(preds, labels)[0]
     spearman_corr = spearmanr(preds, labels)[0]
     return {
@@ -51,10 +49,10 @@ if _has_sklearn:
         "corr": (pearson_corr + spearman_corr) / 2,
     }
 
-    def glue_compute_metrics(task_name, preds, labels):
-        assert len(preds) == len(
-            labels
-        ), f"Predictions and labels have mismatched lengths {len(preds)} and {len(labels)}"
+
+def glue_compute_metrics(task_name, preds, labels):
+    requires_sklearn(glue_compute_metrics)
+    assert len(preds) == len(labels), f"Predictions and labels have mismatched lengths {len(preds)} and {len(labels)}"
     if task_name == "cola":
         return {"mcc": matthews_corrcoef(labels, preds)}
     elif task_name == "sst-2":
@@ -80,10 +78,10 @@ if _has_sklearn:
     else:
         raise KeyError(task_name)
 
-    def xnli_compute_metrics(task_name, preds, labels):
-        assert len(preds) == len(
-            labels
-        ), f"Predictions and labels have mismatched lengths {len(preds)} and {len(labels)}"
+
+def xnli_compute_metrics(task_name, preds, labels):
+    requires_sklearn(xnli_compute_metrics)
+    assert len(preds) == len(labels), f"Predictions and labels have mismatched lengths {len(preds)} and {len(labels)}"
     if task_name == "xnli":
         return {"acc": simple_accuracy(preds, labels)}
     else:

src/transformers/file_utils.py

@@ -133,6 +133,15 @@ try:
 except ImportError:
     _faiss_available = False
 
+try:
+    import sklearn.metrics  # noqa: F401
+
+    import scipy.stats  # noqa: F401
+
+    _has_sklearn = True
+except (AttributeError, ImportError):
+    _has_sklearn = False
+
 
 default_cache_path = os.path.join(torch_cache_home, "transformers")
 
@@ -194,6 +203,88 @@ def is_faiss_available():
     return _faiss_available
 
 
+def is_sklearn_available():
+    return _has_sklearn
+
+
+DATASETS_IMPORT_ERROR = """
+{0} requires the 🤗 Datasets library but it was not found in your enviromnent. You can install it with:
+```
+pip install datasets
+```
+In a notebook or a colab, you can install it by executing a cell with
+```
+!pip install datasets
+```
+then restarting your kernel.
+
+Note that if you have a local folder named `datasets` or a local python file named `datasets.py` in your current
+working directory, python may try to import this instead of the 🤗 Datasets library. You should rename this folder or
+that python file if that's the case.
+"""
+
+
+FAISS_IMPORT_ERROR = """
+{0} requires the faiss library but it was not found in your enviromnent. Checkout the instructions on the
+installation page of its repo: https://github.com/facebookresearch/faiss/blob/master/INSTALL.md and follow the ones
+that match your enviromnent.
+"""
+
+
+PYTORCH_IMPORT_ERROR = """
+{0} requires the PyTorch library but it was not found in your enviromnent. Checkout the instructions on the
+installation page: https://pytorch.org/get-started/locally/ and follow the ones that match your enviromnent.
+"""
+
+
+SKLEARN_IMPORT_ERROR = """
+{0} requires the scikit-learn library but it was not found in your enviromnent. You can install it with:
+```
+pip install -U scikit-learn
+```
+In a notebook or a colab, you can install it by executing a cell with
+```
+!pip install -U scikit-learn
+```
+"""
+
+
+TENSORFLOW_IMPORT_ERROR = """
+{0} requires the TensorFlow library but it was not found in your enviromnent. Checkout the instructions on the
+installation page: https://www.tensorflow.org/install and follow the ones that match your enviromnent.
+"""
+
+
+def requires_datasets(obj):
+    name = obj.__name__ if hasattr(obj, "__name__") else obj.__class__.__name__
+    if not is_datasets_available():
+        raise ImportError(DATASETS_IMPORT_ERROR.format(name))
+
+
+def requires_faiss(obj):
+    name = obj.__name__ if hasattr(obj, "__name__") else obj.__class__.__name__
+    if not is_faiss_available():
+        raise ImportError(FAISS_IMPORT_ERROR.format(name))
+
+
+def requires_pytorch(obj):
+    name = obj.__name__ if hasattr(obj, "__name__") else obj.__class__.__name__
+    if not is_torch_available():
+        raise ImportError(PYTORCH_IMPORT_ERROR.format(name))
+
+
+def requires_sklearn(obj):
+    name = obj.__name__ if hasattr(obj, "__name__") else obj.__class__.__name__
+    if not is_sklearn_available():
+        raise ImportError(SKLEARN_IMPORT_ERROR.format(name))
+
+
+def requires_tf(obj):
+    name = obj.__name__ if hasattr(obj, "__name__") else obj.__class__.__name__
+    if not is_tf_available():
+        raise ImportError(TENSORFLOW_IMPORT_ERROR.format(name))
+
+
 def add_start_docstrings(*docstr):
     def docstring_decorator(fn):
         fn.__doc__ = "".join(docstr) + (fn.__doc__ if fn.__doc__ is not None else "")

src/transformers/retrieval_rag.py

@@ -22,15 +22,23 @@ from typing import Iterable, List, Optional, Tuple
 import numpy as np
 
 from .configuration_rag import RagConfig
-from .file_utils import cached_path, is_datasets_available, is_faiss_available, is_remote_url
+from .file_utils import (
+    cached_path,
+    is_datasets_available,
+    is_faiss_available,
+    is_remote_url,
+    requires_datasets,
+    requires_faiss,
+)
 from .tokenization_rag import RagTokenizer
 from .tokenization_utils_base import BatchEncoding
 from .utils import logging
 
 
-if is_datasets_available() and is_faiss_available():
+if is_datasets_available():
     from datasets import load_dataset
 
+if is_faiss_available():
     import faiss
 
 
@@ -273,6 +281,8 @@ class RagRetriever:
     _init_retrieval = True
 
     def __init__(self, config, question_encoder_tokenizer, generator_tokenizer):
+        requires_datasets(self)
+        requires_faiss(self)
         super().__init__()
         self.index = (
             LegacyIndex(
@@ -301,6 +311,8 @@ class RagRetriever:
 
     @classmethod
     def from_pretrained(cls, retriever_name_or_path, **kwargs):
+        requires_datasets(cls)
+        requires_faiss(cls)
         config = RagConfig.from_pretrained(retriever_name_or_path, **kwargs)
         rag_tokenizer = RagTokenizer.from_pretrained(retriever_name_or_path, config=config)
         question_encoder_tokenizer = rag_tokenizer.question_encoder

utils/check_dummies.py

+# coding=utf-8
+# Copyright 2020 The HuggingFace Inc. team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import os
+import re
+
+
+# All paths are set with the intent you should run this script from the root of the repo with the command
+# python utils/check_dummies.py
+PATH_TO_TRANSFORMERS = "src/transformers"
+
+_re_single_line_import = re.compile(r"\s+from\s+\S*\s+import\s+([^\(\s].*)\n")
+
+DUMMY_CONSTANT = """
+{0} = None
+"""
+
+DUMMY_PT_PRETRAINED_CLASS = """
+class {0}:
+    def __init__(self, *args, **kwargs):
+        requires_pytorch(self)
+
+    @classmethod
+    def from_pretrained(self, *args, **kwargs):
+        requires_pytorch(self)
+"""
+
+DUMMY_PT_CLASS = """
+class {0}:
+    def __init__(self, *args, **kwargs):
+        requires_pytorch(self)
+"""
+
+DUMMY_PT_FUNCTION = """
+def {0}(*args, **kwargs):
+    requires_pytorch({0})
+"""
+
+DUMMY_TF_PRETRAINED_CLASS = """
+class {0}:
+    def __init__(self, *args, **kwargs):
+        requires_tf(self)
+
+    @classmethod
+    def from_pretrained(self, *args, **kwargs):
+        requires_tf(self)
+"""
+
+DUMMY_TF_CLASS = """
+class {0}:
+    def __init__(self, *args, **kwargs):
+        requires_tf(self)
+"""
+
+DUMMY_TF_FUNCTION = """
+def {0}(*args, **kwargs):
+    requires_tf({0})
+"""
+
+
+def read_init():
+    """ Read the init and exctracts PyTorch and TensorFlow objects. """
+    with open(os.path.join(PATH_TO_TRANSFORMERS, "__init__.py"), "r", encoding="utf-8") as f:
+        lines = f.readlines()
+
+    line_index = 0
+    # Find where the PyTorch imports begin
+    pt_objects = []
+    while not lines[line_index].startswith("if is_torch_available():"):
+        line_index += 1
+    line_index += 1
+
+    # Until we unindent, add PyTorch objects to the list
+    while len(lines[line_index]) <= 1 or lines[line_index].startswith("    "):
+        line = lines[line_index]
+        search = _re_single_line_import.search(line)
+        if search is not None:
+            pt_objects += search.groups()[0].split(", ")
+        elif line.startswith("        "):
+            pt_objects.append(line[8:-2])
+        line_index += 1
+
+    # Find where the TF imports begin
+    tf_objects = []
+    while not lines[line_index].startswith("if is_tf_available():"):
+        line_index += 1
+    line_index += 1
+
+    # Until we unindent, add PyTorch objects to the list
+    while len(lines[line_index]) <= 1 or lines[line_index].startswith("    "):
+        line = lines[line_index]
+        search = _re_single_line_import.search(line)
+        if search is not None:
+            tf_objects += search.groups()[0].split(", ")
+        elif line.startswith("        "):
+            tf_objects.append(line[8:-2])
+        line_index += 1
+    return pt_objects, tf_objects
+
+
+def create_dummy_object(name, is_pytorch=True):
+    """ Create the code for the dummy object corresponding to `name`."""
+    _pretrained = [
+        "Config" "ForCausalLM",
+        "ForConditionalGeneration",
+        "ForMaskedLM",
+        "ForMultipleChoice",
+        "ForQuestionAnswering",
+        "ForSequenceClassification",
+        "ForTokenClassification",
+        "Model",
+        "Tokenizer",
+    ]
+    if name.isupper():
+        return DUMMY_CONSTANT.format(name)
+    elif name.islower():
+        return (DUMMY_PT_FUNCTION if is_pytorch else DUMMY_TF_FUNCTION).format(name)
+    else:
+        is_pretrained = False
+        for part in _pretrained:
+            if part in name:
+                is_pretrained = True
+                break
+        if is_pretrained:
+            template = DUMMY_PT_PRETRAINED_CLASS if is_pytorch else DUMMY_TF_PRETRAINED_CLASS
+        else:
+            template = DUMMY_PT_CLASS if is_pytorch else DUMMY_TF_CLASS
+        return template.format(name)
+
+
+def create_dummy_files():
+    """ Create the content of the dummy files. """
+    pt_objects, tf_objects = read_init()
+
+    pt_dummies = "# This file is autogenerated by the command `make fix-copies`, do not edit.\n"
+    pt_dummies += "from ..file_utils import requires_pytorch\n\n"
+    pt_dummies += "\n".join([create_dummy_object(o) for o in pt_objects])
+
+    tf_dummies = "# This file is autogenerated by the command `make fix-copies`, do not edit.\n"
+    tf_dummies += "from ..file_utils import requires_tf\n\n"
+    tf_dummies += "\n".join([create_dummy_object(o, False) for o in tf_objects])
+
+    return pt_dummies, tf_dummies
+
+
+def check_dummies(overwrite=False):
+    """ Check if the dummy files are up to date and maybe `overwrite` with the right content. """
+    pt_dummies, tf_dummies = create_dummy_files()
+    path = os.path.join(PATH_TO_TRANSFORMERS, "utils")
+    pt_file = os.path.join(path, "dummy_pt_objects.py")
+    tf_file = os.path.join(path, "dummy_tf_objects.py")
+
+    with open(pt_file, "r", encoding="utf-8") as f:
+        actual_pt_dummies = f.read()
+    with open(tf_file, "r", encoding="utf-8") as f:
+        actual_tf_dummies = f.read()
+
+    if pt_dummies != actual_pt_dummies:
+        if overwrite:
+            print("Updating transformers.utils.dummy_pt_objects.py as the main __init__ has new objects.")
+            with open(pt_file, "w", encoding="utf-8") as f:
+                f.write(pt_dummies)
+        else:
+            raise ValueError(
+                "The main __init__ has objects that are not present in transformers.utils.dummy_pt_objects.py.",
+                "Run `make fix-copies` to fix this.",
+            )
+
+    if tf_dummies != actual_tf_dummies:
+        if overwrite:
+            print("Updating transformers.utils.dummy_tf_objects.py as the main __init__ has new objects.")
+            with open(tf_file, "w", encoding="utf-8") as f:
+                f.write(tf_dummies)
+        else:
+            raise ValueError(
+                "The main __init__ has objects that are not present in transformers.utils.dummy_pt_objects.py.",
+                "Run `make fix-copies` to fix this.",
+            )
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--fix_and_overwrite", action="store_true", help="Whether to fix inconsistencies.")
+    args = parser.parse_args()
+
+    check_dummies(args.fix_and_overwrite)