Better validators (#97)

* working on improved validators

* full tests for validators

* tweask

* tweaking fields.py

* adding docs

* add history

* fix classmethod validators

docs/examples/validators_complex.py

@@ -0,0 +1,54 @@
+import json
+from typing import List, Set
+
+from pydantic import BaseModel, ValidationError, validator
+
+
+class DemoModel(BaseModel):
+    numbers: List[int] = []
+    people: List[str] = []
+
+    @validator('people', 'numbers', pre=True, whole=True)
+    def json_decode(cls, v):
+        if isinstance(v, str):
+            try:
+                return json.loads(v)
+            except ValueError:
+                pass
+        return v
+
+    @validator('numbers')
+    def check_numbers_low(cls, v):
+        if v > 4:
+            raise ValueError(f'number to large {v} > 4')
+        return v
+
+    @validator('numbers', whole=True)
+    def check_sum_numbers_low(cls, v):
+        if sum(v) > 8:
+            raise ValueError(f'sum of numbers greater than 8')
+        return v
+
+
+print(DemoModel(numbers='[1, 1, 2, 2]'))
+# > DemoModel numbers=[1, 1, 2, 2] people=[]
+
+try:
+    DemoModel(numbers='[1, 2, 5]')
+except ValidationError as e:
+    print(e)
+"""
+error validating input
+numbers:
+  number to large 5 > 4 (error_type=ValueError track=int index=2)
+"""
+
+try:
+    DemoModel(numbers=[3, 3, 3])
+except ValidationError as e:
+    print(e)
+"""
+error validating input
+numbers:
+  sum of numbers greater than 8 (error_type=ValueError track=int)
+"""