Add environment variable backed properties to config

* Allow properties to be defined by environment
variables.

python/cog/config.py

@@ -10,6 +10,7 @@
 from .base_input import BaseInput
 from .base_predictor import BasePredictor
 from .code_xforms import load_module_from_string, strip_model_source_code
+from .env_property import env_property
 from .errors import ConfigDoesNotExist
 from .mode import Mode
 from .predictor import (
@@ -23,6 +24,11 @@
 from .types import CogConfig
 
 COG_YAML_FILE = "cog.yaml"
+COG_PREDICT_TYPE_STUB_ENV_VAR = "COG_PREDICT_TYPE_STUB"
+COG_TRAIN_TYPE_STUB_ENV_VAR = "COG_TRAIN_TYPE_STUB"
+COG_PREDICT_CODE_STRIP_ENV_VAR = "COG_PREDICT_CODE_STRIP"
+COG_TRAIN_CODE_STRIP_ENV_VAR = "COG_TRAIN_CODE_STRIP"
+COG_GPU_ENV_VAR = "COG_GPU"
 PREDICT_METHOD_NAME = "predict"
 TRAIN_METHOD_NAME = "train"
 
@@ -37,6 +43,14 @@ def _method_name_from_mode(mode: Mode) -> str:
     raise ValueError(f"Mode {mode} not recognised for method name mapping")
 
 
+def _env_var_from_mode(mode: Mode) -> str:
+    if mode == Mode.PREDICT:
+        return COG_PREDICT_CODE_STRIP_ENV_VAR
+    elif mode == Mode.TRAIN:
+        return COG_TRAIN_CODE_STRIP_ENV_VAR
+    raise ValueError(f"Mode {mode} not recognised for env var mapping")
+
+
 class Config:
     """A class for reading the cog.yaml properties."""
 
@@ -65,16 +79,19 @@ def _cog_config(self) -> CogConfig:
         return config
 
     @property
+    @env_property(COG_PREDICT_TYPE_STUB_ENV_VAR)
     def predictor_predict_ref(self) -> Optional[str]:
         """Find the predictor ref for the predict mode."""
         return self._cog_config.get(str(Mode.PREDICT))
 
     @property
+    @env_property(COG_TRAIN_TYPE_STUB_ENV_VAR)
     def predictor_train_ref(self) -> Optional[str]:
         """Find the predictor ref for the train mode."""
         return self._cog_config.get(str(Mode.TRAIN))
 
     @property
+    @env_property(COG_GPU_ENV_VAR)
     def requires_gpu(self) -> bool:
         """Whether this cog requires the use of a GPU."""
         return bool(self._cog_config.get("build", {}).get("gpu", False))
@@ -87,6 +104,9 @@ def _predictor_code(
         mode: Mode,
         module_name: str,
     ) -> Optional[str]:
+        source_code = os.environ.get(_env_var_from_mode(mode))
+        if source_code is not None:
+            return source_code
         if sys.version_info >= (3, 9):
             with open(module_path, encoding="utf-8") as file:
                 return strip_model_source_code(file.read(), [class_name], [method_name])

python/cog/env_property.py

@@ -0,0 +1,42 @@
+import os
+from functools import wraps
+from typing import Any, Callable, Optional, TypeVar, Union
+
+R = TypeVar("R")
+
+
+def _get_origin(typ: Any) -> Any:
+    if hasattr(typ, "__origin__"):
+        return typ.__origin__
+    return None
+
+
+def _get_args(typ: Any) -> Any:
+    if hasattr(typ, "__args__"):
+        return typ.__args__
+    return ()
+
+
+def env_property(
+    env_var: str,
+) -> Callable[[Callable[[Any], R]], Callable[[Any], R]]:
+    """Wraps a class property in an environment variable check."""
+
+    def decorator(func: Callable[[Any], R]) -> Callable[[Any], R]:
+        @wraps(func)
+        def wrapper(*args: Any, **kwargs: Any) -> R:
+            result = os.environ.get(env_var)
+            if result is not None:
+                expected_type = func.__annotations__.get("return", str)
+                if (
+                    _get_origin(expected_type) is Optional
+                    or _get_origin(expected_type) is Union
+                ):
+                    expected_type = _get_args(expected_type)[0]
+                return expected_type(result)
+            result = func(*args, **kwargs)
+            return result
+
+        return wrapper
+
+    return decorator

python/tests/test_config.py

@@ -1,12 +1,110 @@
 import os
 import tempfile
 
+import pytest
+
 from cog.config import (
+    COG_GPU_ENV_VAR,
+    COG_PREDICT_CODE_STRIP_ENV_VAR,
+    COG_PREDICT_TYPE_STUB_ENV_VAR,
+    COG_TRAIN_TYPE_STUB_ENV_VAR,
+    COG_YAML_FILE,
     Config,
 )
+from cog.errors import ConfigDoesNotExist
 from cog.mode import Mode
 
 
+def test_predictor_predict_ref_env_var():
+    predict_ref = "predict.py:Predictor"
+    os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR] = predict_ref
+    config = Config()
+    config_predict_ref = config.predictor_predict_ref
+    del os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR]
+    assert (
+        config_predict_ref == predict_ref
+    ), "Predict Reference should come from the environment variable."
+
+
+def test_predictor_predict_ref_no_env_var():
+    if COG_PREDICT_TYPE_STUB_ENV_VAR in os.environ:
+        del os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR]
+    pwd = os.getcwd()
+    with tempfile.TemporaryDirectory() as tmpdir:
+        os.chdir(tmpdir)
+        with open(COG_YAML_FILE, "w", encoding="utf-8") as handle:
+            handle.write("""
+build:
+  python_version: "3.11"
+predict: "predict.py:Predictor"
+""")
+        config = Config()
+        config_predict_ref = config.predictor_predict_ref
+        assert (
+            config_predict_ref == "predict.py:Predictor"
+        ), "Predict Reference should come from the cog config file."
+    os.chdir(pwd)
+
+
+def test_config_no_config_file():
+    if COG_PREDICT_TYPE_STUB_ENV_VAR in os.environ:
+        del os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR]
+    config = Config()
+    with pytest.raises(ConfigDoesNotExist):
+        _ = config.predictor_predict_ref
+
+
+def test_config_initial_values():
+    if COG_PREDICT_TYPE_STUB_ENV_VAR in os.environ:
+        del os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR]
+    config = Config(config={"predict": "predict.py:Predictor"})
+    config_predict_ref = config.predictor_predict_ref
+    assert (
+        config_predict_ref == "predict.py:Predictor"
+    ), "Predict Reference should come from the initial config dictionary."
+
+
+def test_predictor_train_ref_env_var():
+    train_ref = "predict.py:Predictor"
+    os.environ[COG_TRAIN_TYPE_STUB_ENV_VAR] = train_ref
+    config = Config()
+    config_train_ref = config.predictor_train_ref
+    del os.environ[COG_TRAIN_TYPE_STUB_ENV_VAR]
+    assert (
+        config_train_ref == train_ref
+    ), "Train Reference should come from the environment variable."
+
+
+def test_predictor_train_ref_no_env_var():
+    train_ref = "predict.py:Predictor"
+    if COG_TRAIN_TYPE_STUB_ENV_VAR in os.environ:
+        del os.environ[COG_TRAIN_TYPE_STUB_ENV_VAR]
+    config = Config(config={"train": train_ref})
+    config_train_ref = config.predictor_train_ref
+    assert (
+        config_train_ref == train_ref
+    ), "Train Reference should come from the initial config dictionary."
+
+
+def test_requires_gpu_env_var():
+    gpu = True
+    os.environ[COG_GPU_ENV_VAR] = str(gpu)
+    config = Config()
+    config_gpu = config.requires_gpu
+    del os.environ[COG_GPU_ENV_VAR]
+    assert config_gpu, "Requires GPU should come from the environment variable."
+
+
+def test_requires_gpu_no_env_var():
+    if COG_GPU_ENV_VAR in os.environ:
+        del os.environ[COG_GPU_ENV_VAR]
+    config = Config(config={"build": {"gpu": False}})
+    config_gpu = config.requires_gpu
+    assert (
+        not config_gpu
+    ), "Requires GPU should come from the initial config dictionary."
+
+
 def test_get_predictor_ref_predict():
     train_ref = "predict.py:Predictor"
     config = Config(config={"train": train_ref})
@@ -25,6 +123,33 @@ def test_get_predictor_ref_train():
     ), "The predict ref should equal the config predict ref."
 
 
+def test_get_predictor_types_with_env_var():
+    predict_ref = "predict.py:Predictor"
+    os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR] = predict_ref
+    os.environ[COG_PREDICT_CODE_STRIP_ENV_VAR] = """
+from cog import BasePredictor, Path
+from typing import Optional
+from pydantic import BaseModel
+class ModelOutput(BaseModel):
+    success: bool
+    error: Optional[str]
+    segmentedImage: Optional[Path]
+class Predictor(BasePredictor):
+    def predict(self, msg: str) -> ModelOutput:
+        return None
+"""
+    config = Config()
+    input_type, output_type = config.get_predictor_types(Mode.PREDICT)
+    del os.environ[COG_PREDICT_CODE_STRIP_ENV_VAR]
+    del os.environ[COG_PREDICT_TYPE_STUB_ENV_VAR]
+    assert (
+        str(input_type) == "<class 'cog.predictor.Input'>"
+    ), "Predict input type should be the predictor Input."
+    assert (
+        str(output_type) == "<class 'cog.predictor.get_output_type.<locals>.Output'>"
+    ), "Predict output type should be the predictor Output."
+
+
 def test_get_predictor_types():
     with tempfile.TemporaryDirectory() as tmpdir:
         predict_python_file = os.path.join(tmpdir, "predict.py")