Merge pull request #1240 from intgr/fix-choicefield-with-empty-choices

Fix ChoiceField schema type with empty `choices=[]`

drf_spectacular/plumbing.py

@@ -420,8 +420,13 @@ def build_parameter_type(
 def build_choice_field(field) -> _SchemaType:
     choices = list(OrderedDict.fromkeys(field.choices))  # preserve order and remove duplicates
 
-    if all(isinstance(choice, bool) for choice in choices):
-        type: Optional[str] = 'boolean'
+    if field.allow_blank and '' not in choices:
+        choices.append('')
+
+    if not choices:
+        type = None
+    elif all(isinstance(choice, bool) for choice in choices):
+        type = 'boolean'
     elif all(isinstance(choice, int) for choice in choices):
         type = 'integer'
     elif all(isinstance(choice, (int, float, Decimal)) for choice in choices):  # `number` includes `integer`
@@ -432,8 +437,6 @@ def build_choice_field(field) -> _SchemaType:
     else:
         type = None
 
-    if field.allow_blank and '' not in choices:
-        choices.append('')
     if field.allow_null and None not in choices:
         choices.append(None)
 

tests/test_plumbing.py

@@ -398,6 +398,30 @@ def test_choicefield_choices_enum():
     assert schema['enum'] == ['bluepill', 'redpill', '', None]
     assert 'type' not in schema
 
+    schema = build_choice_field(serializers.ChoiceField(
+        choices=[1, 2], allow_blank=True
+    ))
+    assert schema['enum'] == [1, 2, '']
+    assert 'type' not in schema
+
+
+def test_choicefield_empty_choices():
+    schema = build_choice_field(serializers.ChoiceField(choices=[]))
+    assert schema['enum'] == []
+    assert 'type' not in schema
+
+    schema = build_choice_field(serializers.ChoiceField(choices=[], allow_null=True))
+    assert schema['enum'] == [None]
+    assert 'type' not in schema
+
+    schema = build_choice_field(serializers.ChoiceField(choices=[], allow_blank=True))
+    assert schema['enum'] == ['']
+    assert schema['type'] == 'string'
+
+    schema = build_choice_field(serializers.ChoiceField(choices=[], allow_blank=True, allow_null=True))
+    assert schema['enum'] == ['', None]
+    assert schema['type'] == 'string'
+
 
 def test_safe_ref():
     schema = build_basic_type(str)