Make Settings Pydantic and use the power of BaseSettings to simplify CLI

src/blueapi/cli/cli.py

@@ -11,14 +11,15 @@
 from bluesky_stomp.models import Broker
 from observability_utils.tracing import setup_tracing
 from pydantic import ValidationError
+from pydantic_settings.sources import PathType
 from requests.exceptions import ConnectionError
 
 from blueapi import __version__
 from blueapi.cli.format import OutputFormat
 from blueapi.client.client import BlueapiClient
 from blueapi.client.event_bus import AnyEvent, BlueskyStreamingError, EventBusClient
 from blueapi.client.rest import BlueskyRemoteControlError
-from blueapi.config import ApplicationConfig, ConfigLoader
+from blueapi.config import ApplicationConfig
 from blueapi.core import OTLP_EXPORT_ENABLED, DataEvent
 from blueapi.worker import ProgressEvent, Task, WorkerEvent
 
@@ -32,24 +33,17 @@
     "-c", "--config", type=Path, help="Path to configuration YAML file", multiple=True
 )
 @click.pass_context
-def main(ctx: click.Context, config: Path | None | tuple[Path, ...]) -> None:
-    # if no command is supplied, run with the options passed
-
-    config_loader = ConfigLoader(ApplicationConfig)
-    if config is not None:
-        configs = (config,) if isinstance(config, Path) else config
-        for path in configs:
-            if path.exists():
-                config_loader.use_values_from_yaml(path)
-            else:
-                raise FileNotFoundError(f"Cannot find file: {path}")
-
-    ctx.ensure_object(dict)
-    loaded_config: ApplicationConfig = config_loader.load()
-
-    ctx.obj["config"] = loaded_config
+def main(ctx: click.Context, config: PathType) -> None:
+    # Override default yaml_file path in the model_config if `config` is provided
+    ApplicationConfig.model_config["yaml_file"] = config
+    app_config = ApplicationConfig()  # Instantiates with customized sources
+    ctx.obj["config"] = app_config
+
+    # note: this is the key result of the 'main' function, it loaded the config
+    # and due to 'pass context' flag above
+    # it's left for the handler of words that are later in the stdin
     logging.basicConfig(
-        format="%(asctime)s - %(message)s", level=loaded_config.logging.level
+        format="%(asctime)s - %(message)s", level=app_config.logging.level
     )
 
     if ctx.invoked_subcommand is None:
@@ -173,6 +167,7 @@ def listen_to_events(obj: dict) -> None:
             )
         )
     )
+
     fmt = obj["fmt"]
 
     def on_event(

src/blueapi/config.py

@@ -1,16 +1,17 @@
-from collections.abc import Mapping
 from enum import Enum
 from pathlib import Path
-from typing import Any, Generic, Literal, TypeVar
+from typing import Literal
 
-import yaml
 from bluesky_stomp.models import BasicAuthentication
-from pydantic import BaseModel, Field, TypeAdapter, ValidationError
+from pydantic import BaseModel, Field
+from pydantic_settings import BaseSettings, SettingsConfigDict, YamlConfigSettingsSource
 
-from blueapi.utils import BlueapiBaseModel, InvalidConfigError
+from blueapi.utils import BlueapiBaseModel
 
 LogLevel = Literal["NOTSET", "DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"]
 
+DEFAULT_PATH = Path("config.yaml")  # Default YAML file path
+
 
 class SourceKind(str, Enum):
     PLAN_FUNCTIONS = "planFunctions"
@@ -77,7 +78,7 @@ class ScratchConfig(BlueapiBaseModel):
     repositories: list[ScratchRepository] = Field(default_factory=list)
 
 
-class ApplicationConfig(BlueapiBaseModel):
+class ApplicationConfig(BaseSettings, cli_parse_args=True, cli_prog_name="blueapi"):
     """
     Config for the worker application as a whole. Root of
     config tree.
@@ -89,83 +90,18 @@ class ApplicationConfig(BlueapiBaseModel):
     api: RestConfig = Field(default_factory=RestConfig)
     scratch: ScratchConfig | None = None
 
-    def __eq__(self, other: object) -> bool:
-        if isinstance(other, ApplicationConfig):
-            return (
-                (self.stomp == other.stomp)
-                & (self.env == other.env)
-                & (self.logging == other.logging)
-                & (self.api == other.api)
-            )
-        return False
-
-
-C = TypeVar("C", bound=BaseModel)
-
-
-class ConfigLoader(Generic[C]):
-    """
-    Small utility class for loading config from various sources.
-    You must define a config schema as a dataclass (or series of
-    nested dataclasses) that can then be loaded from some combination
-    of default values, dictionaries, YAML/JSON files etc.
-    """
-
-    def __init__(self, schema: type[C]) -> None:
-        self._adapter = TypeAdapter(schema)
-        self._values: dict[str, Any] = {}
-
-    def use_values(self, values: Mapping[str, Any]) -> None:
-        """
-        Use all values provided in the config, override any defaults
-        and values set by previous calls into this class.
-
-        Args:
-            values (Mapping[str, Any]): Dictionary of override values,
-                                        does not need to be exhaustive
-                                        if defaults provided.
-        """
-
-        def recursively_update_map(old: dict[str, Any], new: Mapping[str, Any]) -> None:
-            for key in new:
-                if (
-                    key in old
-                    and isinstance(old[key], dict)
-                    and isinstance(new[key], dict)
-                ):
-                    recursively_update_map(old[key], new[key])
-                else:
-                    old[key] = new[key]
-
-        recursively_update_map(self._values, values)
-
-    def use_values_from_yaml(self, path: Path) -> None:
-        """
-        Use all values provided in a YAML/JSON file in the
-        config, override any defaults and values set by
-        previous calls into this class.
-
-        Args:
-            path (Path): Path to YAML/JSON file
-        """
-
-        with path.open("r") as stream:
-            values = yaml.load(stream, yaml.Loader)
-        self.use_values(values)
-
-    def load(self) -> C:
-        """
-        Finalize and load the config as an instance of the `schema`
-        dataclass.
-
-        Returns:
-            C: Dataclass instance holding config
-        """
-
-        try:
-            return self._adapter.validate_python(self._values)
-        except ValidationError as exc:
-            error_details = "\n".join(str(e) for e in exc.errors())
-            raise InvalidConfigError(
-                f"Something is wrong with the configuration file: \n {error_details}"
-            ) from exc
+    model_config = SettingsConfigDict(
+        env_nested_delimiter="__", yaml_file=DEFAULT_PATH, yaml_file_encoding="utf-8"
+    )
+
+    @classmethod
+    def settings_customize_sources(
+        cls, init_settings, env_settings, file_secret_settings
+    ):
+        path = cls.model_config.get("yaml_file")
+        return (
+            init_settings,
+            YamlConfigSettingsSource(settings_cls=cls, yaml_file=path),
+            env_settings,
+            file_secret_settings,
+        )

src/blueapi/service/config_manager.py

@@ -0,0 +1,26 @@
+# config_manager.py
+
+from blueapi.config import ApplicationConfig
+
+
+class ConfigManager:
+    """Manages application configuration in a way that’s easy to test and mock."""
+
+    _config: ApplicationConfig
+
+    def __init__(self, config: ApplicationConfig = None):
+        if config is None:
+            ApplicationConfig.model_config["yaml_file"] = None
+            config = ApplicationConfig()
+        self._config = config
+
+    def get_config(self) -> ApplicationConfig:
+        """Retrieve the current configuration."""
+        return self._config
+
+    def set_config(self, new_config: ApplicationConfig):
+        """
+        This is a setter function that the main process uses
+        to pass the config into the subprocess
+        """
+        self._config = new_config

src/blueapi/service/interface.py

@@ -9,20 +9,18 @@
 from blueapi.config import ApplicationConfig, StompConfig
 from blueapi.core.context import BlueskyContext
 from blueapi.core.event import EventStream
+from blueapi.service.config_manager import ConfigManager
 from blueapi.service.model import DeviceModel, PlanModel, WorkerTask
 from blueapi.worker.event import TaskStatusEnum, WorkerState
 from blueapi.worker.task import Task
 from blueapi.worker.task_worker import TaskWorker, TrackableTask
 
 """This module provides interface between web application and underlying Bluesky
-context and worker"""
+context and worker
 
+"""
 
-_CONFIG: ApplicationConfig = ApplicationConfig()
-
-
-def config() -> ApplicationConfig:
-    return _CONFIG
+config_manager = ConfigManager()
 
 
 def set_config(new_config: ApplicationConfig):
@@ -34,16 +32,16 @@ def set_config(new_config: ApplicationConfig):
 @cache
 def context() -> BlueskyContext:
     ctx = BlueskyContext()
-    ctx.with_config(config().env)
+    env_config = config_manager.get_config().env
+    ctx.with_config(env_config)
     return ctx
 
 
 @cache
 def worker() -> TaskWorker:
-    worker = TaskWorker(
-        context(),
-        broadcast_statuses=config().env.events.broadcast_status_events,
-    )
+    env_config = config_manager.get_config().env
+    should_broadcast_status_events: bool = env_config.events.broadcast_status_events
+    worker = TaskWorker(context(), broadcast_statuses=should_broadcast_status_events)
     worker.start()
     return worker
 
@@ -79,7 +77,7 @@ def stomp_client() -> StompClient | None:
 def setup(config: ApplicationConfig) -> None:
     """Creates and starts a worker with supplied config"""
 
-    set_config(config)
+    config_manager.set_config(config)
 
     # Eagerly initialize worker and messaging connection
 

src/blueapi/utils/__init__.py

@@ -1,5 +1,4 @@
 from .base_model import BlueapiBaseModel, BlueapiModelConfig, BlueapiPlanModelConfig
-from .invalid_config_error import InvalidConfigError
 from .modules import load_module_all
 from .serialization import serialize
 from .thread_exception import handle_all_exceptions
@@ -11,5 +10,4 @@
     "BlueapiBaseModel",
     "BlueapiModelConfig",
     "BlueapiPlanModelConfig",
-    "InvalidConfigError",
 ]