modifying how rules work a bit, adding WasChanged.

.travis.yml

@@ -5,4 +5,4 @@ python:
   - "2.7"
   - "3.3"
 install: "pip install -r requirements.txt"
-script: "uranium test"
+script: "uranium test"

tests/decorators/test_rules.py → tests/rules/test_rules.py

@@ -1,14 +1,29 @@
-from uranium import rule
+from uranium.rules import rule, RuleBase
+
+
+class AlwaysPass(RuleBase):
+
+    def before(self, build):
+        return True
+
+    def after(self, build):
+        pass
+
+
+class AlwaysFail(RuleBase):
+
+    def before(self, build):
+        return False
+
+    def after(self, build):
+        pass
 
 
 def test_rule_does_not_execute(build):
 
     g = []
 
-    def rule_func(build):
-        return True
-
-    @rule(rule_func)
+    @rule(AlwaysPass())
     def main(build):
         g.append("main")
 
@@ -23,14 +38,8 @@ def test_all_true_multiple_rules(build):
 
     g = []
 
-    def rule_func(build):
-        return True
-
-    def rule_func_2(build):
-        return True
-
-    @rule(rule_func)
-    @rule(rule_func_2)
+    @rule(AlwaysPass())
+    @rule(AlwaysPass())
     def main(build):
         g.append("main")
 
@@ -45,14 +54,8 @@ def test_one_false_multiple_rules(build):
 
     g = []
 
-    def rule_func(build):
-        return True
-
-    def rule_func_2(build):
-        return False
-
-    @rule(rule_func)
-    @rule(rule_func_2)
+    @rule(AlwaysPass())
+    @rule(AlwaysFail())
     def main(build):
         g.append("main")
 

uranium/__init__.py

@@ -7,4 +7,7 @@
 import setuptools
 
 from .remote import get_remote_script
-from .decorators import task_requires, rule
+from .decorators import task_requires
+from .rules import rule
+
+__all__ = ["get_remote_script", "task_requires", "rule"]

uranium/decorators.py

@@ -1,5 +1,4 @@
 import functools
-from .experimental import experimental
 
 
 def task_requires(func_or_func_name):
@@ -24,37 +23,3 @@ def func(build):
         return func
 
     return decorator
-
-
-@experimental
-def rule(rule_func):
-    """
-    the rule decorator is used to add a rule function to the task.
-
-    the rule function should accept a build object, and should return
-    True in the case where a build is required.
-
-    multiple rules can be added to a task. If any of the rules return false,
-    the task will be re-executed.
-    """
-    key = "_uranium_rules"
-
-    def decorator(f):
-
-        if hasattr(f, key):
-            getattr(f, key).append(rule_func)
-            return f
-
-        rules = [rule_func]
-
-        @functools.wraps(f)
-        def func(build):
-            if all((r(build) for r in rules)):
-                return 0
-            return f(build)
-
-        setattr(func, key, rules)
-
-        return func
-
-    return decorator

uranium/rules/__init__.py

@@ -0,0 +1,60 @@
+import functools
+from abc import ABCMeta, abstractmethod
+from ..experimental import experimental
+
+
+class RuleBase(object):
+    """
+    an example of a rule.
+
+    * func gets set during the initialization process.
+    """
+    func = None
+
+    __metaclass__ = ABCMeta
+
+    @abstractmethod
+    def before(self, build):
+        pass
+
+    @abstractmethod
+    def after(self, build):
+        pass
+
+
+@experimental
+def rule(rule_object):
+    """
+    the rule decorator is used to add a rule function to the task.
+
+    the rule function should accept a build object, and should return
+    True in the case where a build is required.
+
+    multiple rules can be added to a task. If any of the rules return false,
+    the task will be re-executed.
+    """
+    key = "_uranium_rules"
+
+    def decorator(f):
+        rule_object.func = f
+
+        if hasattr(f, key):
+            getattr(f, key).append(rule_object)
+            return f
+
+        rules = [rule_object]
+
+        @functools.wraps(f)
+        def func(build):
+            if all((r.before(build) for r in rules)):
+                return 0
+            return_value = f(build)
+            for r in rules:
+                r.after(build)
+            return return_value
+
+        setattr(func, key, rules)
+
+        return func
+
+    return decorator

uranium/rules/was_changed.py

@@ -0,0 +1,45 @@
+import os
+import time
+from . import RuleBase
+KEY = "_uranium.rules.was_changed"
+
+
+class WasChanged(RuleBase):
+
+    def __init__(self, path):
+        self._path = path
+
+    def before(self, build):
+        previous_timestamp = build.history.get(self.key)
+        if not previous_timestamp:
+            return False
+        current_timestamp = self._get_timestamp(self.path)
+        return current_timestamp > previous_timestamp
+
+    def after(self, build):
+        current_timestamp = self._get_timestamp(self.path)
+        build.history[self.key] = current_timestamp
+
+    @property
+    def key(self):
+        return "{}.{}.{}".format(
+            KEY, self._path, self.func.__name__
+        )
+
+    @classmethod
+    def _get_timestamp(cls, path):
+        """ return the timestamp as a UTC datetime object. """
+        if os.path.isdir(path):
+            return cls._get_dir_timestamp(path)
+        else:
+            return os.path.getmtime(path)
+
+    @classmethod
+    def _get_dir_timestamp(cls, path):
+        oldest_timestamp = time.time()
+        for root, _, filename in os.walk(path):
+            f_path = os.path.join(root, filename)
+            ts = os.path.getmtime(f_path)
+            if ts < oldest_timestamp:
+                oldest_timestamp = ts
+        return oldest_timestamp