plugin: Introduce HookRegistry.

This is the layer that keeps track of the different groups of hooks and
can filter them before runtime. The idea here is that you'll be able
to do things like skip hooks that require network access when you don't
have it, or skip CPU-intensive hooks when you don't need them, etc.

conservancy_beancount/plugin/__init__.py

@@ -14,6 +14,8 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+import importlib
+
 import beancount.core.data as bc_data
 
 __plugins__ = ['run']
@@ -24,18 +26,61 @@ class HookRegistry:
         'Posting',
     ])
 
-    @classmethod
-    def group_by_directive(cls, hooks_seq):
-        hooks_map = {key: [] for key in cls.DIRECTIVES}
-        for hook in hooks_seq:
-            for key in cls.DIRECTIVES & hook.HOOK_GROUPS:
-                hooks_map[key].append(hook)
-        return hooks_map
+    def __init__(self):
+        self.group_hooks_map = {key: set() for key in self.DIRECTIVES}
+
+    def add_hook(self, hook_cls):
+        hook_groups = list(hook_cls.HOOK_GROUPS)
+        assert self.DIRECTIVES.intersection(hook_groups)
+        hook_groups.append('all')
+        for name_attr in ['HOOK_NAME', 'METADATA_KEY', '__name__']:
+            try:
+                hook_name = getattr(hook_cls, name_attr)
+            except AttributeError:
+                pass
+            else:
+                hook_groups.append(hook_name)
+                break
+        for key in hook_groups:
+            self.group_hooks_map.setdefault(key, set()).add(hook_cls)
+        return hook_cls  # to allow use as a decorator
+
+    def import_hooks(self, mod_name, *hook_names, package=__module__):
+        module = importlib.import_module(mod_name, package)
+        for hook_name in hook_names:
+            self.add_hook(getattr(module, hook_name))
+
+    def group_by_directive(self, config_str=''):
+        config_str = config_str.strip()
+        if not config_str:
+            config_str = 'all'
+        elif config_str.startswith('-'):
+            config_str = 'all ' + config_str
+        available_hooks = set()
+        for token in config_str.split():
+            if token.startswith('-'):
+                update_available = available_hooks.difference_update
+                key = token[1:]
+            else:
+                update_available = available_hooks.update
+                key = token
+            try:
+                update_set = self.group_hooks_map[key]
+            except KeyError:
+                raise ValueError("configuration refers to unknown hooks {!r}".format(key)) from None
+            else:
+                update_available(update_set)
+        return {key: [hook() for hook in self.group_hooks_map[key] & available_hooks]
+                for key in self.DIRECTIVES}
 
 
-def run(entries, options_map, config):
+HOOK_REGISTRY = HookRegistry()
+HOOK_REGISTRY.import_hooks('.meta_expense_allocation', 'MetaExpenseAllocation')
+HOOK_REGISTRY.import_hooks('.meta_tax_implication', 'MetaTaxImplication')
+
+def run(entries, options_map, config='', hook_registry=HOOK_REGISTRY):
     errors = []
-    hooks = HookRegistry.group_by_directive(config)
+    hooks = hook_registry.group_by_directive(config)
     for entry in entries:
         entry_type = type(entry).__name__
         for hook in hooks[entry_type]:

conservancy_beancount/plugin/core.py

@@ -67,6 +67,7 @@ class MetadataEnum:
 
 
 class PostingChecker:
+    HOOK_GROUPS = frozenset(['Posting', 'metadata'])
     ACCOUNTS = ('',)
     TXN_DATE_RANGE = _GenericRange(DEFAULT_START_DATE, DEFAULT_STOP_DATE)
     VALUES_ENUM = {}

tests/test_plugin_HookRegistry.py

@@ -0,0 +1,53 @@
+"""Test main plugin's HookRegistry"""
+# Copyright © 2020  Brett Smith
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import pytest
+
+from . import testutil
+
+from conservancy_beancount import plugin
+
+def hook_names(hooks, key):
+    return {type(hook).__name__ for hook in hooks[key]}
+
+def test_default_registrations():
+    hooks = plugin.HOOK_REGISTRY.group_by_directive()
+    post_hook_names = hook_names(hooks, 'Posting')
+    assert len(post_hook_names) >= 2
+    assert 'MetaExpenseAllocation' in post_hook_names
+    assert 'MetaTaxImplication' in post_hook_names
+
+def test_exclude_single():
+    hooks = plugin.HOOK_REGISTRY.group_by_directive('-expenseAllocation')
+    post_hook_names = hook_names(hooks, 'Posting')
+    assert post_hook_names
+    assert 'MetaExpenseAllocation' not in post_hook_names
+
+def test_exclude_group_then_include_single():
+    hooks = plugin.HOOK_REGISTRY.group_by_directive('-metadata expenseAllocation')
+    post_hook_names = hook_names(hooks, 'Posting')
+    assert 'MetaExpenseAllocation' in post_hook_names
+    assert 'MetaTaxImplication' not in post_hook_names
+
+def test_include_group_then_exclude_single():
+    hooks = plugin.HOOK_REGISTRY.group_by_directive('metadata -taxImplication')
+    post_hook_names = hook_names(hooks, 'Posting')
+    assert 'MetaExpenseAllocation' in post_hook_names
+    assert 'MetaTaxImplication' not in post_hook_names
+
+def test_unknown_group_name():
+    with pytest.raises(ValueError):
+        plugin.HOOK_REGISTRY.group_by_directive('UnKnownTestGroup')

tests/test_plugin_run.py

@@ -21,7 +21,9 @@ from . import testutil
 from conservancy_beancount import plugin
 
 CONFIG_MAP = {}
+HOOK_REGISTRY = plugin.HookRegistry()
 
+@HOOK_REGISTRY.add_hook
 class TransactionCounter:
     HOOK_GROUPS = frozenset(['Transaction', 'counter'])
 
@@ -29,6 +31,7 @@ class TransactionCounter:
         return ['txn:{}'.format(id(txn))]
 
 
+@HOOK_REGISTRY.add_hook
 class PostingCounter(TransactionCounter):
     HOOK_GROUPS = frozenset(['Posting', 'counter'])
 
@@ -44,8 +47,6 @@ def map_errors(errors):
     return retval
 
 def test_with_multiple_hooks():
-    txn_counter = TransactionCounter()
-    post_counter = PostingCounter()
     in_entries = [
         testutil.Transaction(postings=[
             ('Income:Donations', -25),
@@ -56,14 +57,13 @@ def test_with_multiple_hooks():
             ('Liabilites:CreditCard', -10),
         ]),
     ]
-    out_entries, errors = plugin.run(in_entries, CONFIG_MAP, [txn_counter, post_counter])
+    out_entries, errors = plugin.run(in_entries, CONFIG_MAP, '', HOOK_REGISTRY)
     assert len(out_entries) == 2
     errmap = map_errors(errors)
     assert len(errmap.get('txn', '')) == 2
     assert len(errmap.get('post', '')) == 4
 
 def test_with_posting_hooks_only():
-    post_counter = PostingCounter()
     in_entries = [
         testutil.Transaction(postings=[
             ('Income:Donations', -25),
@@ -74,7 +74,7 @@ def test_with_posting_hooks_only():
             ('Liabilites:CreditCard', -10),
         ]),
     ]
-    out_entries, errors = plugin.run(in_entries, CONFIG_MAP, [post_counter])
+    out_entries, errors = plugin.run(in_entries, CONFIG_MAP, 'Posting', HOOK_REGISTRY)
     assert len(out_entries) == 2
     errmap = map_errors(errors)
     assert len(errmap.get('txn', '')) == 0