Support Decimal fields while deserializing. (#903)

Support Decimal fields while de-serializing and add section to docs.

Co-authored-by: David Glick <[email protected]>

docs/source/usage/serialization.md

@@ -31,16 +31,28 @@ Since JSON does not have native support for dates and times, the Python and Zope
 | `DateTime("2015/11/23 19:45:55")`    | `"2015-11-23T19:45:55"` |
 
 
+## Decimal Type
+
+The [Python Decimal type](https://docs.python.org/3/library/decimal.html) supports correctly rounded decimal floating point arithmetic.
+To keep the precision, serializing the value to JSON results in a string.
+
+| Python                               | JSON                    |
+| ------------------------------------ | ----------------------- |
+| `Decimal("3.14159265359")`           | `"3.14159265359"`       |
+
+
 ## RichText fields
 
 RichText fields will be serialized as follows:
 
 A `RichTextValue` such as the following:
 
 ```python
-RichTextValue(u'<p>Hallöchen</p>',
-              mimeType='text/html',
-              outputMimeType='text/html')
+RichTextValue(
+    "<p>Hallöchen</p>",
+    mimeType="text/html",
+    outputMimeType="text/html",
+)
 ```
 
 …will be serialized to:

news/903.bugfix

@@ -0,0 +1,2 @@
+Fix missing `Decimal` field deserializer.
+[jensens]

src/plone/restapi/deserializer/configure.zcml

@@ -18,6 +18,7 @@
   <adapter factory=".dxfields.TimedeltaFieldDeserializer" />
   <adapter factory=".dxfields.NamedFieldDeserializer" />
   <adapter factory=".dxfields.RichTextFieldDeserializer" />
+  <adapter factory=".dxfields.DecimalFieldDeserializer" />
   <adapter factory=".blocks.BlocksJSONFieldDeserializer" />
 
   <subscriber

src/plone/restapi/deserializer/dxfields.py

@@ -1,4 +1,5 @@
 from datetime import timedelta
+from decimal import Decimal
 from plone.app.contenttypes.interfaces import ILink
 from plone.app.textfield.interfaces import IRichText
 from plone.app.textfield.value import RichTextValue
@@ -18,6 +19,7 @@
 from zope.schema.interfaces import IChoice
 from zope.schema.interfaces import ICollection
 from zope.schema.interfaces import IDatetime
+from zope.schema.interfaces import IDecimal
 from zope.schema.interfaces import IDict
 from zope.schema.interfaces import IField
 from zope.schema.interfaces import IFromUnicode
@@ -296,3 +298,13 @@ def __call__(self, value):
         )
         self.field.validate(value)
         return value
+
+
+@implementer(IFieldDeserializer)
+@adapter(IDecimal, IDexterityContent, IBrowserRequest)
+class DecimalFieldDeserializer(DefaultFieldDeserializer):
+    def __call__(self, value):
+        if not isinstance(value, Decimal):
+            value = Decimal(value)
+        self.field.validate(value)
+        return value

src/plone/restapi/tests/dxtypes.py

@@ -144,7 +144,6 @@ def vocabularyRequireingContextFactory(context):
 
 
 class IDXTestDocumentSchema(model.Schema):
-
     # zope.schema fields
     test_ascii_field = schema.ASCII(required=False)
     test_asciiline_field = schema.ASCIILine(required=False)
@@ -310,13 +309,11 @@ class DXTestDocument(Item):
 
 @provider(IFormFieldProvider)
 class ITestBehavior(model.Schema):
-
     test_behavior_field = schema.TextLine(required=False)
     # Add nav_title to test if it gets substituted in Navigation service
     nav_title = schema.TextLine(required=False)
 
 
 @provider(IFormFieldProvider)
 class ITestAnnotationsBehavior(model.Schema):
-
     test_annotations_behavior_field = schema.TextLine(required=False)

src/plone/restapi/tests/test_dxfield_deserializer.py

@@ -184,6 +184,16 @@ def test_float_deserialization_returns_float(self):
         self.assertTrue(isinstance(value, float), "Not a <float>")
         self.assertEqual(1.0, value)
 
+    def test_float_deserialization_returns_decimal(self):
+        value = self.deserialize("test_decimal_field", 1.111)
+        self.assertTrue(isinstance(value, Decimal), "Not a <Decimal>")
+        # a float from JSON to decimal can not work properly, so you would get
+        # real floating point precision only
+        self.assertEqual(
+            Decimal("1.1109999999999999875655021241982467472553253173828125"),
+            value,
+        )
+
     def test_frozenset_deserialization_returns_frozenset(self):
         value = self.deserialize("test_frozenset_field", ["foo", "bar"])
         self.assertTrue(isinstance(value, frozenset), "Not a <frozenset>")

src/plone/restapi/tests/test_dxfield_serializer.py

@@ -104,10 +104,10 @@ def test_datetime_field_serialization_returns_unicode(self):
         self.assertTrue(isinstance(value, str), "Not an <unicode>")
         self.assertEqual("2015-06-20T13:22:04", value)
 
-    def test_decimal_field_serialization_returns_unicode(self):
-        value = self.serialize("test_decimal_field", Decimal("1.1"))
-        self.assertTrue(isinstance(value, str), "Not an <unicode>")
-        self.assertEqual("1.1", value)
+    def test_decimal_field_serialization_returns_str(self):
+        value = self.serialize("test_decimal_field", Decimal("1.111"))
+        self.assertTrue(isinstance(value, str), "Not an <str>")
+        self.assertEqual("1.111", value)
 
     def test_dict_field_serialization_returns_dict(self):
         value = self.serialize(