feat(rules): build the scoped query in one place

A rule stores no scope. The hook supplies tag:new, a dry run supplies
nothing. The parentheses around the rule's own query are what stop a
disjunction of senders from escaping the scope and matching everything.

1 files changed, 19 insertions, 0 deletions

diff --git a/mailrules.py b/mailrules.py
index 8c65708..dbb80a5 100755
--- a/mailrules.py
+++ b/mailrules.py
@@ -126,6 +126,25 @@ def load(path=None):
     return store
 
 
+def scoped_query(rule, scope):
+    """The rule's query narrowed by `scope`, or the bare query when scope is
+    empty.
+
+    The parentheses are load-bearing. notmuch's `and` binds tighter than
+    `or`, so `tag:new and a or b` means `(tag:new and a) or b`: a rule that
+    is a disjunction of senders would escape its scope and match the whole
+    corpus. Do not remove them, and do not build this string anywhere else.
+    """
+    if not scope:
+        return rule.query
+    return f"{scope} and ({rule.query})"
+
+
+def tag_arguments(rule):
+    """The +tag/-tag arguments for `notmuch tag`, adds before removes."""
+    return [f"+{t}" for t in rule.add] + [f"-{t}" for t in rule.remove]
+
+
 def save(store, path=None):
     """Write the store atomically: a temp file in the same directory, then
     rename. Rename within a filesystem is atomic, so a concurrent reader sees