Aded default response formatting

Author: jtc42

labthings/core/utilities.py

@@ -2,8 +2,16 @@
 import re
 import base64
 import operator
+import sys
 from functools import reduce
 
+try:
+    from collections.abc import OrderedDict
+except ImportError:
+    from collections import OrderedDict
+
+PY3 = sys.version_info > (3,)
+
 
 def get_docstring(obj):
     ds = obj.__doc__

labthings/server/representations.py

@@ -0,0 +1,28 @@
+from flask import make_response, current_app
+from json import dumps
+
+from ..core.utilities import PY3
+
+
+def output_json(data, code, headers=None):
+    """Makes a Flask response with a JSON encoded body"""
+
+    settings = current_app.config.get("RESTFUL_JSON", {})
+
+    # If we're in debug mode, and the indent is not set, we set it to a
+    # reasonable value here.  Note that this won't override any existing value
+    # that was set.  We also set the "sort_keys" value.
+    if current_app.debug:
+        settings.setdefault("indent", 4)
+        settings.setdefault("sort_keys", not PY3)
+
+    # always end the json dumps with a new line
+    # see https://github.com/mitsuhiko/flask/pull/1262
+    dumped = dumps(data, **settings) + "\n"
+
+    resp = make_response(dumped, code)
+    resp.headers.extend(headers or {})
+    return resp
+
+
+DEFAULT_REPRESENTATIONS = [("application/json", output_json)]

labthings/server/utilities.py

@@ -1,15 +1,19 @@
-from ..core.utilities import get_docstring, get_summary
-
-from .view import View
+from ..core.utilities import get_summary
 
+from werkzeug.http import HTTP_STATUS_CODES
 from flask import current_app
 
 
+def http_status_message(code):
+    """Maps an HTTP status code to the textual status"""
+    return HTTP_STATUS_CODES.get(code, "")
+
+
 def description_from_view(view_class):
     summary = get_summary(view_class)
 
     methods = []
-    for method_key in View.methods:
+    for method_key in view_class.methods:
         if hasattr(view_class, method_key):
             methods.append(method_key.upper())
 
@@ -24,3 +28,23 @@ def description_from_view(view_class):
 
 def view_class_from_endpoint(endpoint: str):
     return current_app.view_functions[endpoint].view_class
+
+
+def unpack(value):
+    """Return a three tuple of data, code, and headers"""
+    if not isinstance(value, tuple):
+        return value, 200, {}
+
+    try:
+        data, code, headers = value
+        return data, code, headers
+    except ValueError:
+        pass
+
+    try:
+        data, code = value
+        return data, code, {}
+    except ValueError:
+        pass
+
+    return value, 200, {}

labthings/server/view.py

@@ -1,4 +1,11 @@
 from flask.views import MethodView
+from flask import request
+from werkzeug.wrappers import Response as ResponseBase
+
+from labthings.core.utilities import OrderedDict
+
+from labthings.server.utilities import unpack
+from labthings.server.representations import DEFAULT_REPRESENTATIONS
 
 
 class View(MethodView):
@@ -15,6 +22,10 @@ class View(MethodView):
     def __init__(self, *args, **kwargs):
         MethodView.__init__(self, *args, **kwargs)
 
+        # Set the default representations
+        # TODO: Inherit from parent LabThing. See original flask_restful implementation
+        self.representations = OrderedDict(DEFAULT_REPRESENTATIONS)
+
     def doc(self):
         docs = {"operations": {}}
         if hasattr(self, "__apispec__"):
@@ -25,3 +36,31 @@ def doc(self):
                 docs["operations"][meth] = {}
                 docs["operations"][meth] = getattr(self, meth).__apispec__
         return docs
+
+    def dispatch_request(self, *args, **kwargs):
+        meth = getattr(self, request.method.lower(), None)
+
+        # If the request method is HEAD and we don't have a handler for it
+        # retry with GET.
+        if meth is None and request.method == "HEAD":
+            meth = getattr(self, "get", None)
+
+        assert meth is not None, "Unimplemented method %r" % request.method
+
+        # Generate basic response
+        resp = meth(*args, **kwargs)
+
+        if isinstance(resp, ResponseBase):  # There may be a better way to test
+            return resp
+
+        representations = self.representations or OrderedDict()
+
+        # noinspection PyUnresolvedReferences
+        mediatype = request.accept_mimetypes.best_match(representations, default=None)
+        if mediatype in representations:
+            data, code, headers = unpack(resp)
+            resp = representations[mediatype](data, code, headers)
+            resp.headers["Content-Type"] = mediatype
+            return resp
+
+        return resp

labthings/server/views/docs/__init__.py

@@ -1,11 +1,11 @@
 from flask import (
-    abort,
     url_for,
     jsonify,
     render_template,
     Blueprint,
     current_app,
     request,
+    make_response,
 )
 
 from labthings.core.utilities import get_docstring
@@ -14,8 +14,6 @@
 from ...find import current_labthing
 from ...spec import rule_to_path, rule_to_params
 
-import os
-
 
 class APISpecView(View):
     """
@@ -35,7 +33,7 @@ class SwaggerUIView(View):
     """
 
     def get(self):
-        return render_template("swagger-ui.html")
+        return make_response(render_template("swagger-ui.html"))
 
 
 class W3CThingDescriptionView(View):