Improve PushProcessor::getPushRuleGlobRegex (#4764)

* Improve PushProcessor::getPushRuleGlobRegex

Fix cache key not taking non-pattern parameters into account
Use lookarounds to ensure the word boundary isn't treated as part of the match

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Add tests

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

spec/unit/pushprocessor.spec.ts

@@ -1,3 +1,19 @@
+/*
+Copyright 2025 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 import * as utils from "../test-utils/test-utils";
 import { type IActionsObject, PushProcessor } from "../../src/pushprocessor";
 import {
@@ -1004,3 +1020,25 @@ describe("rewriteDefaultRules", () => {
         ]);
     });
 });
+
+describe("getPushRuleGlobRegex", () => {
+    it("should not confuse flags in cache", () => {
+        const pattern = "Test";
+        const regex1 = PushProcessor.getPushRuleGlobRegex(pattern, false, "i");
+        const regex2 = PushProcessor.getPushRuleGlobRegex(pattern, false, "g");
+        const regex3 = PushProcessor.getPushRuleGlobRegex(pattern, false, "i");
+
+        expect(regex1.flags).toBe("i");
+        expect(regex2.flags).toBe("g");
+
+        expect(regex1).not.toEqual(regex2);
+        expect(regex1).toEqual(regex3);
+    });
+
+    it("should not include word boundary in match", () => {
+        const pattern = "@room";
+        const regex = PushProcessor.getPushRuleGlobRegex(pattern, true);
+        const input = "Foo @room Bar";
+        expect(input.split(regex)).toEqual(["Foo ", "@room", " Bar"]);
+    });
+});

src/pushprocessor.ts

@@ -313,19 +313,21 @@ export class PushProcessor {
      * No cache invalidation is present currently,
      * as this will be inherently bounded to the size of the user's own push rules.
      * @param pattern - the glob pattern to convert to a RegExp
-     * @param alignToWordBoundary - whether to align the pattern to word boundaries, as specified for `content.body` matches
+     * @param alignToWordBoundary - whether to align the pattern to word boundaries,
+     *     as specified for `content.body` matches, will use lookaround assertions to ensure the match only includes the pattern
      * @param flags - the flags to pass to the RegExp constructor, defaults to case-insensitive
      */
     public static getPushRuleGlobRegex(pattern: string, alignToWordBoundary = false, flags = "i"): RegExp {
-        const [prefix, suffix] = alignToWordBoundary ? ["(^|\\W)", "(\\W|$)"] : ["^", "$"];
+        const [prefix, suffix] = alignToWordBoundary ? ["(?<=^|\\W)", "(?=\\W|$)"] : ["^", "$"];
+        const cacheKey = `${alignToWordBoundary}-${flags}-${pattern}`;
 
-        if (!PushProcessor.cachedGlobToRegex[pattern]) {
-            PushProcessor.cachedGlobToRegex[pattern] = new RegExp(
+        if (!PushProcessor.cachedGlobToRegex[cacheKey]) {
+            PushProcessor.cachedGlobToRegex[cacheKey] = new RegExp(
                 prefix + "(" + globToRegexp(pattern) + ")" + suffix,
                 flags,
             );
         }
-        return PushProcessor.cachedGlobToRegex[pattern];
+        return PushProcessor.cachedGlobToRegex[cacheKey];
     }
 
     /**