Merge pull request #110 from labthings/persistent-property

Thing Setting syntax and implementation overhaul

Author: julianstirling

docs/source/lt_core_concepts.rst

@@ -10,21 +10,26 @@ At its core LabThings FastAPI is a server-based framework. To use LabThings Fast
 
 The server API is accessed over an HTTP requests, allowing client code (see below) to be written in any language that can send an HTTP request.
 
-Client Code
------------
-
-Clients or client code (Not to be confused with a :class:`.ThingClient`, see below) is the terminology used to describe any software that uses HTTP requests to access the LabThing Server. Clients can be written in any language that supports an HTTP request. However, LabThings FastAPI provides additional functionality that makes writing client code in Python easier.
-
 Everything is a Thing
 ---------------------
 
-As described in :doc:`wot_core_concepts`, a Thing represents a piece of hardware or software. LabThings-FastAPI automatically generates a `Thing Description`_ to describe each Thing. Each function offered by the Thing is either a Property, Action, or Event. These are termed "interaction affordances" in WoT_ terminology.
+As described in :doc:`wot_core_concepts`, a Thing represents a piece of hardware or software. LabThings-FastAPI automatically generates a `Thing Description`_ to describe each Thing. Each function offered by the Thing is either a Property or Action (LabThings-FastAPI does not yet support Events). These are termed "interaction affordances" in WoT_ terminology.
 
 Code on the LabThings FastAPI Server is composed of Things, however these can call generic Python functions/classes. The entire HTTP API served by the server is defined by :class:`.Thing` objects. As such the full API is composed of the actions and properties (and perhaps eventually events) defined in each Thing.
 
 _`Thing Description`: wot_core_concepts#thing
 _`WoT`: wot_core_concepts
 
+Properties vs Settings
+----------------------
+
+A Thing in LabThings-FastAPI can have Settings as well as Properties. "Setting" is LabThings-FastAPI terminology for a "Property" with a value that persists after the server is restarted. All Settings are Properties, and -- except for persisting after a server restart -- Settings are identical to any other Properties.
+
+Client Code
+-----------
+
+Clients or client code (Not to be confused with a :class:`.ThingClient`, see below) is the terminology used to describe any software that uses HTTP requests to access the LabThing Server. Clients can be written in any language that supports an HTTP request. However, LabThings FastAPI provides additional functionality that makes writing client code in Python easier.
+
 ThingClients
 ------------
 

docs/source/quickstart/counter.py

@@ -1,7 +1,7 @@
 import time
 from labthings_fastapi.thing import Thing
 from labthings_fastapi.decorators import thing_action
-from labthings_fastapi.descriptors import PropertyDescriptor
+from labthings_fastapi.descriptors import ThingProperty
 
 
 class TestThing(Thing):
@@ -24,7 +24,7 @@ def slowly_increase_counter(self) -> None:
             time.sleep(1)
             self.increment_counter()
 
-    counter = PropertyDescriptor(
+    counter = ThingProperty(
         model=int, initial_value=0, readonly=True, description="A pointless counter"
     )
 

examples/counter.py

@@ -1,7 +1,7 @@
 import time
 from labthings_fastapi.thing import Thing
 from labthings_fastapi.decorators import thing_action
-from labthings_fastapi.descriptors import PropertyDescriptor
+from labthings_fastapi.descriptors import ThingProperty
 from labthings_fastapi.server import ThingServer
 
 
@@ -25,7 +25,7 @@ def slowly_increase_counter(self) -> None:
             time.sleep(1)
             self.increment_counter()
 
-    counter = PropertyDescriptor(
+    counter = ThingProperty(
         model=int, initial_value=0, readonly=True, description="A pointless counter"
     )
 

examples/demo_thing_server.py

@@ -4,7 +4,7 @@
 from labthings_fastapi.thing import Thing
 from labthings_fastapi.decorators import thing_action
 from labthings_fastapi.server import ThingServer
-from labthings_fastapi.descriptors import PropertyDescriptor
+from labthings_fastapi.descriptors import ThingProperty
 from pydantic import Field
 from fastapi.responses import HTMLResponse
 
@@ -60,11 +60,11 @@ def slowly_increase_counter(self):
             time.sleep(1)
             self.increment_counter()
 
-    counter = PropertyDescriptor(
+    counter = ThingProperty(
         model=int, initial_value=0, readonly=True, description="A pointless counter"
     )
 
-    foo = PropertyDescriptor(
+    foo = ThingProperty(
         model=str,
         initial_value="Example",
         description="A pointless string for demo purposes.",

examples/opencv_camera_server.py

@@ -3,7 +3,7 @@
 
 from fastapi import FastAPI
 from fastapi.responses import HTMLResponse, StreamingResponse
-from labthings_fastapi.descriptors.property import PropertyDescriptor
+from labthings_fastapi.descriptors.property import ThingProperty
 from labthings_fastapi.thing import Thing
 from labthings_fastapi.decorators import thing_action, thing_property
 from labthings_fastapi.server import ThingServer
@@ -279,7 +279,7 @@ def exposure(self, value):
         with self._cap_lock:
             self._cap.set(cv.CAP_PROP_EXPOSURE, value)
 
-    last_frame_index = PropertyDescriptor(int, initial_value=-1)
+    last_frame_index = ThingProperty(int, initial_value=-1)
 
     mjpeg_stream = MJPEGStreamDescriptor(ringbuffer_size=10)
 

examples/picamera2_camera_server.py

@@ -4,7 +4,7 @@
 
 from pydantic import BaseModel, BeforeValidator
 
-from labthings_fastapi.descriptors.property import PropertyDescriptor
+from labthings_fastapi.descriptors.property import ThingProperty
 from labthings_fastapi.thing import Thing
 from labthings_fastapi.decorators import thing_action, thing_property
 from labthings_fastapi.server import ThingServer
@@ -24,14 +24,12 @@
 logging.basicConfig(level=logging.INFO)
 
 
-class PicameraControl(PropertyDescriptor):
+class PicameraControl(ThingProperty):
     def __init__(
         self, control_name: str, model: type = float, description: Optional[str] = None
     ):
         """A property descriptor controlling a picamera control"""
-        PropertyDescriptor.__init__(
-            self, model, observable=False, description=description
-        )
+        ThingProperty.__init__(self, model, observable=False, description=description)
         self.control_name = control_name
         self._getter
 
@@ -84,20 +82,20 @@ def __init__(self, device_index: int = 0):
         self.device_index = device_index
         self.camera_configs: dict[str, dict] = {}
 
-    stream_resolution = PropertyDescriptor(
+    stream_resolution = ThingProperty(
         tuple[int, int],
         initial_value=(1640, 1232),
         description="Resolution to use for the MJPEG stream",
     )
-    image_resolution = PropertyDescriptor(
+    image_resolution = ThingProperty(
         tuple[int, int],
         initial_value=(3280, 2464),
         description="Resolution to use for still images (by default)",
     )
-    mjpeg_bitrate = PropertyDescriptor(
+    mjpeg_bitrate = ThingProperty(
         int, initial_value=0, description="Bitrate for MJPEG stream (best left at 0)"
     )
-    stream_active = PropertyDescriptor(
+    stream_active = ThingProperty(
         bool,
         initial_value=False,
         description="Whether the MJPEG stream is active",
@@ -116,7 +114,7 @@ def __init__(self, device_index: int = 0):
     exposure_time = PicameraControl(
         "ExposureTime", int, description="The exposure time in microseconds"
     )
-    sensor_modes = PropertyDescriptor(list[SensorMode], readonly=True)
+    sensor_modes = ThingProperty(list[SensorMode], readonly=True)
 
     def __enter__(self):
         self._picamera = picamera2.Picamera2(camera_num=self.device_index)
@@ -219,7 +217,7 @@ def exposure(self) -> float:
     def exposure(self, value):
         raise NotImplementedError()
 
-    last_frame_index = PropertyDescriptor(int, initial_value=-1)
+    last_frame_index = ThingProperty(int, initial_value=-1)
 
     mjpeg_stream = MJPEGStreamDescriptor(ringbuffer_size=10)
 

pyproject.toml

@@ -51,6 +51,15 @@ artifacts = ["src/*.json"]
 [tool.hatch.build.targets.wheel]
 artifacts = ["src/*.json"]
 
+[tool.pytest.ini_options]
+addopts = [
+    "--cov=labthings_fastapi",
+    "--cov-report=term",
+    "--cov-report=xml:coverage.xml",
+    "--cov-report=html:htmlcov",
+    "--cov-report=lcov",
+]
+
 [tool.ruff]
 target-version = "py310"
 

src/labthings_fastapi/client/in_server.py

@@ -16,7 +16,7 @@
 from pydantic import BaseModel
 from labthings_fastapi.descriptors.action import ActionDescriptor
 
-from labthings_fastapi.descriptors.property import PropertyDescriptor
+from labthings_fastapi.descriptors.property import ThingProperty
 from labthings_fastapi.utilities import attributes
 from . import PropertyClientDescriptor
 from ..thing import Thing
@@ -123,15 +123,15 @@ def action_method(self, **kwargs):
 
 
 def add_property(
-    attrs: dict[str, Any], property_name: str, property: PropertyDescriptor
+    attrs: dict[str, Any], property_name: str, property: ThingProperty
 ) -> None:
     """Add a property to a DirectThingClient subclass"""
     attrs[property_name] = property_descriptor(
         property_name,
         property.model,
         description=property.description,
         writeable=not property.readonly,
-        readable=True,  # TODO: make this configurable in PropertyDescriptor
+        readable=True,  # TODO: make this configurable in ThingProperty
     )
 
 
@@ -163,8 +163,7 @@ def init_proxy(self, request: Request, **dependencies: Mapping[str, Any]):
     }
     dependencies: list[inspect.Parameter] = []
     for name, item in attributes(thing_class):
-        if isinstance(item, PropertyDescriptor):
-            # TODO: What about properties that don't use descriptors? Fall back to http?
+        if isinstance(item, ThingProperty):
             add_property(client_attrs, name, item)
         elif isinstance(item, ActionDescriptor):
             if actions is None or name in actions:

src/labthings_fastapi/decorators/__init__.py

@@ -36,7 +36,8 @@
 from typing import Optional, Callable
 from ..descriptors import (
     ActionDescriptor,
-    PropertyDescriptor,
+    ThingProperty,
+    ThingSetting,
     EndpointDescriptor,
     HTTPMethod,
 )
@@ -71,20 +72,54 @@ def thing_action(func: Optional[Callable] = None, **kwargs):
         return partial(mark_thing_action, **kwargs)
 
 
-def thing_property(func: Callable) -> PropertyDescriptor:
-    """Mark a method of a Thing as a Property
+def thing_property(func: Callable) -> ThingProperty:
+    """Mark a method of a Thing as a LabThings Property
 
-    We replace the function with a `Descriptor` that's a
-    subclass of `PropertyDescriptor`
+    This should be used as a decorator with a getter and a setter
+    just like a standard python property decorator. If extra functionality
+    is not required in the decorator, then using the ThingProperty class
+    directly may allow for clearer code
 
-    TODO: try https://stackoverflow.com/questions/54413434/type-hinting-with-descriptors
+    As properties are accessed over the HTTP API they need to be JSON serialisable
+    only return standard python types, or Pydantic BaseModels
     """
+    # Replace the function with a `Descriptor` that's a `ThingProperty`
+    return ThingProperty(
+        return_type(func),
+        readonly=True,
+        observable=False,
+        getter=func,
+    )
+
 
-    class PropertyDescriptorSubclass(PropertyDescriptor):
-        def __get__(self, obj, objtype=None):
-            return super().__get__(obj, objtype)
+def thing_setting(func: Callable) -> ThingSetting:
+    """Mark a method of a Thing as a LabThings Setting.
 
-    return PropertyDescriptorSubclass(
+    A setting is a property that persists between runs.
+
+    This should be used as a decorator with a getter and a setter
+    just like a standard python property decorator. If extra functionality
+    is not required in the decorator, then using the ThingSetting class
+    directly may allow for clearer code where the property works like a normal variable.
+
+    When creating a Setting using this decorator you must always create a setter
+    as it is used to load the value from disk.
+
+    As settings are accessed over the HTTP API and saved to disk they need to be
+    JSON serialisable only return standard python types, or Pydantic BaseModels.
+
+    If the type is a pydantic BaseModel, then the setter must also be able to accept
+    the dictionary representation of this BaseModel as this is what will be used to
+    set the Setting when loading from disk on starting the server.
+
+    Note: If a setting is mutated rather than set, this will not trigger saving.
+    For example: if a Thing has a setting called `dictsetting` holding the dictionary
+    `{"a": 1, "b": 2}` then `self.dictsetting = {"a": 2, "b": 2}` would trigger saving
+    but `self.dictsetting[a] = 2` would not, as the setter for `dictsetting` is never
+    called.
+    """
+    # Replace the function with a `Descriptor` that's a `ThingSetting`
+    return ThingSetting(
         return_type(func),
         readonly=True,
         observable=False,

src/labthings_fastapi/descriptors/__init__.py

@@ -1,4 +1,5 @@
 from .action import ActionDescriptor as ActionDescriptor
-from .property import PropertyDescriptor as PropertyDescriptor
+from .property import ThingProperty as ThingProperty
+from .property import ThingSetting as ThingSetting
 from .endpoint import EndpointDescriptor as EndpointDescriptor
 from .endpoint import HTTPMethod as HTTPMethod