Allow field projection (#85)

* Allow to select fields

* Added doctest

* Changelog updated

Author: ramonski

docs/changelog.rst

@@ -4,6 +4,7 @@ Changelog
 2.7.0 (unreleased)
 ------------------
 
+- #85 Allow field projection
 - #81 Support second-level precision on searches against DateIndex
 - #83 Fetch multiple items by UID
 - #80 Precise timestamp filtering and sorting for created/modified fields

src/senaite/jsonapi/api.py

@@ -298,10 +298,16 @@ def make_items_for(brains_or_objects, endpoint=None, complete=False):
     # check if the user wants to include children
     include_children = req.get_children(False)
 
+    # optional field projection: ?fields=uid,id,title,...
+    # empty set means no projection (full object returned)
+    fields = req.get_fields()
+
     def extract_data(brain_or_object):
         info = get_info(brain_or_object, endpoint=endpoint, complete=complete)
         if include_children and is_folderish(brain_or_object):
             info.update(get_children_info(brain_or_object, complete=complete))
+        if fields:
+            info = {k: info[k] for k in fields if k in info}
         return info
 
     return map(extract_data, brains_or_objects)

src/senaite/jsonapi/request.py

@@ -228,6 +228,20 @@ def get_uids():
     return [v.strip() for v in value.split(",") if v.strip()]
 
 
+def get_fields():
+    """Returns the set of field names requested via the 'fields' parameter.
+
+    Accepts a comma-separated string, e.g. ``?fields=uid,id,title``.
+    Returns an empty set when the parameter is absent or blank.
+    An empty set means no projection is applied and the full object is
+    returned (unchanged behaviour).
+    """
+    value = get("fields", "")
+    if not value:
+        return set()
+    return set(v.strip() for v in value.split(",") if v.strip())
+
+
 def get_request_data():
     """ extract and convert the json data from the request
 

src/senaite/jsonapi/tests/doctests/field_projection.rst

@@ -0,0 +1,188 @@
+FIELD PROJECTION
+----------------
+
+Running this test from the buildout directory:
+
+    bin/test test_doctests -t field_projection
+
+
+Test Setup
+~~~~~~~~~~
+
+Needed Imports:
+
+    >>> import json
+    >>> import transaction
+    >>> from plone.app.testing import setRoles
+    >>> from plone.app.testing import TEST_USER_ID
+    >>> from bika.lims import api
+
+Functional Helpers:
+
+    >>> def get(url):
+    ...     browser.open("{}/{}".format(api_url, url))
+    ...     return browser.contents
+
+    >>> def get_count(response):
+    ...     data = json.loads(response)
+    ...     return data.get("count")
+
+    >>> def get_item_keys(response, index=0):
+    ...     data = json.loads(response)
+    ...     items = data.get("items", [])
+    ...     if not items:
+    ...         return []
+    ...     return sorted(items[index].keys())
+
+Variables:
+
+    >>> portal = self.portal
+    >>> portal_url = portal.absolute_url()
+    >>> api_url = "{}/@@API/senaite/v1".format(portal_url)
+    >>> browser = self.getBrowser()
+    >>> setRoles(portal, TEST_USER_ID, ["LabManager", "Manager"])
+
+Create two Client objects and commit so they are indexed:
+
+    >>> c1 = api.create(portal.clients, "Client", title="Alpha Lab", ClientID="AL")
+    >>> c2 = api.create(portal.clients, "Client", title="Beta Lab", ClientID="BL")
+    >>> uid1 = api.get_uid(c1)
+    >>> uid2 = api.get_uid(c2)
+    >>> transaction.commit()
+
+
+Basic projection — only requested fields are returned
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Requesting ``uid,id,title`` returns exactly those three keys in each item:
+
+    >>> response = get("client?fields=uid,id,title")
+    >>> keys = get_item_keys(response)
+    >>> "uid" in keys
+    True
+    >>> "id" in keys
+    True
+    >>> "title" in keys
+    True
+
+Fields that were not requested are absent:
+
+    >>> "portal_type" in keys
+    False
+    >>> "url" in keys
+    False
+    >>> "path" in keys
+    False
+
+
+Projection with complete=1
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Field projection applies after object wake-up, so ``complete=1`` fields
+are also subject to it:
+
+    >>> response = get("client?complete=1&fields=uid,title,ClientID")
+    >>> keys = get_item_keys(response)
+    >>> "uid" in keys
+    True
+    >>> "title" in keys
+    True
+    >>> "ClientID" in keys
+    True
+
+Fields outside the requested set are still excluded:
+
+    >>> "id" in keys
+    False
+    >>> "portal_type" in keys
+    False
+
+
+Requested content is correct
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The projected values match the objects that were created:
+
+    >>> response = get("client?fields=uid,title")
+    >>> data = json.loads(response)
+    >>> titles = sorted(item["title"] for item in data["items"])
+    >>> titles
+    [u'Alpha Lab', u'Beta Lab']
+
+
+Projection with a single requested field
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Requesting only ``title`` returns items with exactly one key:
+
+    >>> response = get("client?fields=title")
+    >>> keys = get_item_keys(response)
+    >>> keys
+    [u'title']
+
+
+Unknown fields are silently omitted
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A field name that does not exist on the object is ignored rather than
+raising an error:
+
+    >>> response = get("client?fields=uid,nonexistent_field")
+    >>> keys = get_item_keys(response)
+    >>> "uid" in keys
+    True
+    >>> "nonexistent_field" in keys
+    False
+
+
+No projection when fields parameter is absent
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Without a ``fields`` parameter the full object is returned, including
+the standard set of metadata fields:
+
+    >>> response = get("client?uids={}".format(uid1))
+    >>> keys = get_item_keys(response)
+    >>> "uid" in keys
+    True
+    >>> "url" in keys
+    True
+    >>> "portal_type" in keys
+    True
+
+
+Projection combined with batch UID fetch
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``?fields=`` and ``?uids=`` can be combined in a single request:
+
+    >>> response = get("client?uids={},{}&fields=uid,title".format(uid1, uid2))
+    >>> get_count(response)
+    2
+    >>> data = json.loads(response)
+    >>> keys = sorted(data["items"][0].keys())
+    >>> keys
+    [u'title', u'uid']
+    >>> "Alpha Lab" in response
+    True
+    >>> "Beta Lab" in response
+    True
+
+
+Projection on the generic /search route
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The ``fields`` parameter works on the ``/search`` endpoint as well:
+
+    >>> response = get(
+    ...     "search?portal_type=Client&fields=uid,id,title"
+    ... )
+    >>> keys = get_item_keys(response)
+    >>> "uid" in keys
+    True
+    >>> "id" in keys
+    True
+    >>> "title" in keys
+    True
+    >>> "portal_type" in keys
+    False