Add callback to adjust() to make it observable by callers

fmf/base.py

@@ -6,6 +6,7 @@
 import subprocess
 from io import open
 from pprint import pformat as pretty
+from typing import Any, Dict, Optional, Protocol
 
 import jsonschema
 from ruamel.yaml import YAML
@@ -29,6 +30,25 @@
 #  Metadata
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+
+class AdjustCallback(Protocol):
+    """
+    A callback for per-rule notifications made by Tree.adjust()
+
+    Function be be called for every rule inspected by adjust().
+    It will be given three arguments: fmf tree being inspected,
+    current adjust rule, and whether the rule was skipped (``None``),
+    applied (``True``) or not applied (``False``).
+    """
+
+    def __call__(
+            self,
+            node: 'Tree',
+            rule: Dict[str, Any],
+            applied: Optional[bool]) -> None:
+        pass
+
+
 class Tree:
     """ Metadata Tree """
 
@@ -320,7 +340,7 @@ def update(self, data):
         log.debug("Data for '{0}' updated.".format(self))
         log.data(pretty(self.data))
 
-    def adjust(self, context, key='adjust', undecided='skip'):
+    def adjust(self, context, key='adjust', undecided='skip', decision_callback=None):
         """
         Adjust tree data based on provided context and rules
 
@@ -334,6 +354,10 @@ class describing the environment context. By default, the key
         context dimension is not defined. By default, such rules are
         skipped. In order to raise the fmf.context.CannotDecide
         exception in such cases use undecided='raise'.
+
+        Optional 'decision_callback' callback would be called for every adjust
+        rule inspected, with three arguments: current fmf node, current
+        adjust rule, and whether it was applied or not.
         """
 
         # Check context sanity
@@ -363,6 +387,8 @@ class describing the environment context. By default, the key
             if not isinstance(rule, dict):
                 raise utils.FormatError("Adjust rule should be a dictionary.")
 
+            original_rule = rule.copy()
+
             # Missing 'when' means always enabled rule
             try:
                 condition = rule.pop('when')
@@ -382,13 +408,22 @@ class describing the environment context. By default, the key
             # Apply remaining rule attributes if context matches
             try:
                 if context.matches(condition):
+                    if decision_callback:
+                        decision_callback(self, original_rule, True)
+
                     self._merge_special(self.data, rule)
 
                     # First matching rule wins, skip the rest unless continue
                     if not continue_:
                         break
+                else:
+                    if decision_callback:
+                        decision_callback(self, original_rule, False)
             # Handle undecided rules as requested
             except fmf.context.CannotDecide:
+                if decision_callback:
+                    decision_callback(self, original_rule, None)
+
                 if undecided == 'skip':
                     continue
                 elif undecided == 'raise':
@@ -400,7 +435,7 @@ class describing the environment context. By default, the key
 
         # Adjust all child nodes as well
         for child in self.children.values():
-            child.adjust(context, key, undecided)
+            child.adjust(context, key, undecided, decision_callback=decision_callback)
 
     def get(self, name=None, default=None):
         """

tests/unit/test_adjust.py

@@ -1,4 +1,5 @@
 import copy
+from unittest.mock import MagicMock
 
 import pytest
 from ruamel.yaml import YAML
@@ -204,3 +205,19 @@ def test_continue_default(self, full, fedora):
         full.adjust(fedora)
         extend = full.find('/extend')
         assert extend.get('require') == ['one', 'two', 'three']
+
+    def test_adjust_callback(self, mini, fedora, centos):
+        # From the mini tree
+        rule = mini.data['adjust']
+
+        mock_callback = MagicMock(name='<mock>callback')
+        mini.adjust(fmf.Context(), decision_callback=mock_callback)
+        mock_callback.assert_called_once_with(mini, rule, None)
+
+        mock_callback = MagicMock(name='<mock>callback')
+        mini.adjust(fedora, decision_callback=mock_callback)
+        mock_callback.assert_called_once_with(mini, rule, False)
+
+        mock_callback = MagicMock(name='<mock>callback')
+        mini.adjust(centos, decision_callback=mock_callback)
+        mock_callback.assert_called_once_with(mini, rule, True)