Added refine method

.gitignore

@@ -160,3 +160,5 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+.vscode

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 All notable changes to this project will be documented in this file.
 
-The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 > This changelog was generated some commits after the [v1.0.0 tag](https://github.com/Naapperas/zon/releases/tag/v1.0.0), so the changelog will have some inconsistencies until the next release.
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added the `zon.traits.collection` file which contains the `ZonCollection` class: this is the base class for all collection types.
 - Added testing for `ZonCollection` and added more tests for `ZonString`.
 - Scripts that automate the building and publishing of the package to PyPI.
+- Added `refine` method to the base `Zon` class.
 
 ### Changed
 - `ZonString` now inherits from `ZonCollection` instead of `Zon`.

tests/base_test.py

@@ -0,0 +1,16 @@
+import pytest
+
+import zon
+
+@pytest.fixture
+def validator():
+    return zon.anything()
+
+def test_refine(validator):
+
+    assert validator.validate(1)
+
+    refined_validator = validator.refine(lambda x: x == 1)
+
+    assert refined_validator.validate(1)
+    assert not refined_validator.validate(2) 

zon/base.py

@@ -9,6 +9,10 @@
 ValidationRule = Callable[[T], bool]
 
 
+class AggregateValidator:
+    """A validator that aggregates multiple validation calls"""
+
+
 class Zon(ABC):
     """Base class for all Zons.
     A Zon is the basic unit of validation in Zon.
@@ -97,6 +101,40 @@ def and_also(self, zon: "Zon") -> "ZonAnd":
     def __and__(self, zon: "Zon") -> "ZonAnd":
         return self.and_also(zon)
 
+    def refine(self, refinement: Callable[[T], bool]) -> "Self":
+        """Creates a new Zon that validates the data with the supplied refinement.
+
+        A refinement is a function that takes a piece of data and returns True if the data is valid or throws otherwise.
+
+        Args:
+            refinement (Callable[[T], bool]): the refinement to be applied.
+
+        Returns:
+            ZonRefined: a new validator that validates the data with the supplied refinement.
+        """
+        _clone = self._clone()
+
+        def _refinement_validate(data):
+            try:
+                return refinement(data)
+            except ValidationError as e:
+                _clone._add_error(e)
+                return False
+
+        if "_refined_" not in _clone.validators:
+            _clone.validators["_refined_"] = _refinement_validate
+        else:
+            current_refinement = _clone.validators["_refined_"]
+
+            def _refined_validator(data):
+                return current_refinement(data) and _refinement_validate(
+                    data
+                )
+
+            _clone.validators["_refined_"] = _refined_validator
+
+        return _clone
+
 
 def optional(zon: Zon) -> "ZonOptional":
     """Marks this validation chain as optional, making it so the data supplied need not be defined.
@@ -129,7 +167,7 @@ def _default_validate(self, data):
 class ZonAnd(Zon):
     """A Zon that validates that the data is valid for both this Zon and the supplied Zon."""
 
-    def __init__(self, zon1, zon2):
+    def __init__(self, zon1: Zon, zon2: Zon):
         super().__init__()
         self.zon1 = zon1
         self.zon2 = zon2