Support DX Decimal fields via a field manager

docs/changelog.rst

@@ -15,6 +15,7 @@ Changelog
    applied. Uninstalling from the same panel removes the PAS plugin
    and the per-user JWT signing secrets.
 
+- #114 Support DX Decimal fields via a field manager
 - #109 Add a partition operation endpoint
 - #106 Fix single-valued UID reference fields not settable through the JSON API
 - #112 Allow updating the Laboratory through the API

src/senaite/jsonapi/configure.zcml

@@ -271,6 +271,12 @@
       factory=".fieldmanagers.DatetimeFieldManager"
       />
 
+  <!-- Adapter for DX Decimal Fields -->
+  <adapter
+      for="zope.schema.interfaces.IDecimal"
+      factory=".fieldmanagers.DecimalFieldManager"
+      />
+
   <!-- Adapter for DX Duration (Timedelta) Fields -->
   <adapter
       for="senaite.core.schema.interfaces.IDurationField"

src/senaite/jsonapi/datamanagers.py

@@ -31,14 +31,20 @@
 from senaite.jsonapi import api
 from senaite.jsonapi.interfaces import IDataManager
 from senaite.jsonapi.interfaces import IFieldManager
+from senaite.jsonapi.fieldmanagers import DecimalFieldManager
 from senaite.jsonapi.fieldmanagers import DurationFieldManager
 from senaite.jsonapi.fieldmanagers import UIDReferenceFieldMixin
 
 # Field managers that normalize the incoming value (resolve UIDs, coerce
-# a duration mapping to a timedelta, ...). For these the raw set<Name>
-# mutator would store the value unconverted, so the data manager must go
-# through the field manager instead of the setter.
-NORMALIZING_FIELD_MANAGERS = (UIDReferenceFieldMixin, DurationFieldManager)
+# a duration mapping to a timedelta, a number to a Decimal, ...). For
+# these the raw set<Name> mutator would store the value unconverted, so
+# the data manager must go through the field manager instead of the
+# setter.
+NORMALIZING_FIELD_MANAGERS = (
+    UIDReferenceFieldMixin,
+    DurationFieldManager,
+    DecimalFieldManager,
+)
 
 
 class BaseDataManager(object):

src/senaite/jsonapi/fieldmanagers.py

@@ -25,6 +25,8 @@
 from AccessControl import Unauthorized
 from bika.lims import api as bika_api
 from datetime import timedelta
+from decimal import Decimal
+from decimal import InvalidOperation
 from DateTime import DateTime
 from Products.Archetypes.utils import mapply
 from senaite.core.schema.uidreferencefield import UIDReferenceField
@@ -202,6 +204,49 @@ def to_mapping(value):
         }
 
 
+class DecimalFieldManager(ZopeSchemaFieldManager):
+    """Adapter to get/set DX Decimal field values.
+
+    The stored value is a `decimal.Decimal`, which JSON has no type for.
+    A price arrives as a string, a float or an integer and every one of
+    them fails the field's own validation, so a Decimal field could not
+    be written through the API at all. Accept all three on set and
+    serialize back to a string, which is the only JSON form that keeps
+    the exact value.
+    """
+    interface.implements(IFieldManager)
+
+    def set(self, instance, value, **kw):
+        value = self.to_decimal(value)
+        self.field.validate(value)
+        return self.field.set(instance, value)
+
+    def json_data(self, instance, default=None):
+        value = self.get(instance)
+        if not isinstance(value, Decimal):
+            return default
+        return str(value)
+
+    @staticmethod
+    def to_decimal(value):
+        """Coerce a JSON value to Decimal, leaving anything else alone.
+
+        A value that is not a number is handed on untouched so the field
+        reports it, rather than this adapter raising an error of its own
+        for a value the field would describe better.
+        """
+        if value is None or isinstance(value, Decimal):
+            return value
+        if isinstance(value, bool):
+            return value
+        if isinstance(value, (six.string_types, int, float)):
+            try:
+                return Decimal(str(value).strip())
+            except (InvalidOperation, ValueError):
+                return value
+        return value
+
+
 class RichTextFieldManager(ZopeSchemaFieldManager):
     """Adapter to get/set the value of Rich Text Fields
     """

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

@@ -350,6 +350,30 @@ directly; it accepts a `{days, hours, minutes, seconds}` mapping:
     >>> sample_point.sampling_frequency
     datetime.timedelta(7)
 
+A DX Decimal field has no JSON type either. It takes the number as a
+string, which is the only form that keeps the exact value, and also
+accepts a plain number:
+
+    >>> data = {"portal_type": "AnalysisProfile",
+    ...         "parent_path": api.get_path(portal.setup.analysisprofiles),
+    ...         "title": "Basic Panel",
+    ...         "analysis_profile_price": u"24.00",
+    ...         "analysis_profile_vat": 7}
+    >>> profile = create_json(data)
+    >>> profile.analysis_profile_price
+    Decimal('24.00')
+    >>> profile.analysis_profile_vat
+    Decimal('7')
+
+It reads back as a string:
+
+    >>> from senaite.jsonapi.interfaces import IFieldManager
+    >>> from senaite.jsonapi.api import get_field
+    >>> field = get_field(profile, "analysis_profile_price")
+    >>> IFieldManager(field).json_data(profile)
+    '24.00'
+
+
 
 Creating a Sample
 ~~~~~~~~~~~~~~~~~