Let LabThing object handle choice of JSON encoder

Author: Joel Collins

src/labthings/labthing.py

@@ -51,29 +51,32 @@ def __init__(
         types: list = None,
         version: str = "0.0.0",
         format_flask_exceptions: bool = True,
+        json_encoder=LabThingsJSONEncoder,
     ):
         if types is None:
             types = []
         self.app = app  # Becomes a Flask app
         self.sockets = None  # Becomes a Socket(app) websocket handler
 
-        self.components = {}
+        self.components = (
+            {}
+        )  # Dictionary of attached component objects, available to extensions
 
-        self.extensions = {}
+        self.extensions = {}  # Dictionary of LabThings extension objects
 
         self.actions = Pool()  # Pool of threads for Actions
 
-        self.events = {}
+        self.events = {}  # Dictionary of Event affordances
 
-        self.views = []
-        self._property_views = {}
-        self._action_views = {}
+        self.views = []  # List of View classes
+        self._property_views = {}  # Dictionary of PropertyView views
+        self._action_views = {}  # Dictionary of ActionView views
 
-        self.subscribers = set()
+        self.subscribers = set()  # Set of connected event subscribers
 
-        self.endpoints = set()
+        self.endpoints = set()  # Set of endpoint strings
 
-        self.url_prefix = prefix
+        self.url_prefix = prefix  # Global URL prefix for all LabThings views
 
         for t in types:
             if ";" in t:
@@ -97,7 +100,7 @@ def __init__(
         # Representation formatter map
         self.representations = DEFAULT_REPRESENTATIONS
 
-        # API Spec
+        # OpenAPI spec for Swagger docs
         self.spec = APISpec(
             title=self.title,
             version=self.version,
@@ -108,6 +111,9 @@ def __init__(
         # Thing description
         self.thing_description = ThingDescription()
 
+        # JSON encoder class
+        self.json_encoder = json_encoder
+
         if app is not None:
             self.init_app(app)
 
@@ -162,7 +168,7 @@ def init_app(self, app):
             error_handler.init_app(app)
 
         # Custom JSON encoder
-        app.json_encoder = LabThingsJSONEncoder
+        app.json_encoder = self.json_encoder
 
         # Add resources, if registered before tying to a Flask app
         if len(self.views) > 0:

src/labthings/representations.py

@@ -2,16 +2,20 @@
 from collections import OrderedDict
 
 from .json.encoder import LabThingsJSONEncoder, encode_json
+from .json.encoder import JSONEncoder as FlaskJSONEncoder
+from .find import current_labthing
 from .utilities import PY3
 
 
 def output_json(data, code, headers=None):
     """Makes a Flask response with a JSON encoded body, using app JSON settings"""
 
     settings = current_app.config.get("LABTHINGS_JSON", {})
-    encoder = (
-        current_app.config.get("LABTHINGS_JSON_ENCODER", {}) or LabThingsJSONEncoder
-    )
+
+    if current_labthing():
+        encoder = current_labthing().json_encoder
+    else:
+        encoder = getattr(current_app, "json_encoder", None) or FlaskJSONEncoder
 
     if current_app.debug:
         settings.setdefault("indent", 4)