From f36d2b8496f32b4f52bfc3cf9a1c3248af777f4e Mon Sep 17 00:00:00 2001
From: Raymond Hill <gorhill@users.noreply.github.com>
Date: Wed, 1 Oct 2025 11:35:15 -0400
Subject: [PATCH] Add ability to test against regex in `JSONPath` expressions

Related discussion:
https://github.com/uBlockOrigin/uAssets/issues/30157#issuecomment-3356048999
---
 src/js/jsonpath.js | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/src/js/jsonpath.js b/src/js/jsonpath.js
index 020aab0bf..1126f8fc1 100644
--- a/src/js/jsonpath.js
+++ b/src/js/jsonpath.js
@@ -49,6 +49,7 @@
  *   - ^=: stringified value starts with 
  *   - $=: stringified value ends with
  *   - *=: stringified value includes
+ *   - =/.../: regular expression matches
  * 
  * - Examples (from "JSONPath examples" at reference link)
  *   - .store.book[*].author
@@ -376,7 +377,7 @@ export class JSONPath {
                 continue;
             }
             if ( c0 === 0x27 /* ' */ ) {
-                const r = this.#consumeQuotedIdentifier(query, i+1);
+                const r = this.#untilChar(query, 0x27 /* ' */, i+1)
                 if ( r === undefined ) { return; }
                 keys.push(r.s);
                 i = r.i;
@@ -397,22 +398,27 @@ export class JSONPath {
         }
         return { s: keys.length === 1 ? keys[0] : keys, i };
     }
-    #consumeQuotedIdentifier(query, i) {
+    #consumeUnquotedIdentifier(query, i) {
+        const match = this.#reUnquotedIdentifier.exec(query.slice(i));
+        if ( match === null ) { return; }
+        return match[0];
+    }
+    #untilChar(query, targetCharCode, i) {
         const len = query.length;
         const parts = [];
         let beg = i, end = i;
         for (;;) {
             if ( end === len ) { return; }
             const c = query.charCodeAt(end);
-            if ( c === 0x27 /* ' */ ) {
+            if ( c === targetCharCode ) {
                 parts.push(query.slice(beg, end));
                 end += 1;
                 break;
             }
             if ( c === 0x5C /* \ */ && (end+1) < len ) {
                 parts.push(query.slice(beg, end));
-                const d = query.chatCodeAt(end+1);
-                if ( d === 0x27 || d === 0x5C ) {
+                const d = query.charCodeAt(end+1);
+                if ( d === targetCharCode || d === 0x5C ) {
                     end += 1;
                     beg = end;
                 }
@@ -421,12 +427,20 @@ export class JSONPath {
         }
         return { s: parts.join(''), i: end };
     }
-    #consumeUnquotedIdentifier(query, i) {
-        const match = this.#reUnquotedIdentifier.exec(query.slice(i));
-        if ( match === null ) { return; }
-        return match[0];
-    }
     #compileExpr(query, step, i) {
+        if ( query.startsWith('=/', i) ) {
+            const r = this.#untilChar(query, 0x2F /* / */, i+2);
+            if ( r === undefined ) { return i; }
+            const match = /^[i]/.exec(query.slice(r.i));
+            try {
+                step.rval = new RegExp(r.s, match && match[0] || undefined);
+            } catch {
+                return i;
+            }
+            step.op = 're';
+            if ( match ) { r.i += match[0].length; }
+            return r.i;
+        }
         const match = this.#reExpr.exec(query.slice(i));
         if ( match === null ) { return i; }
         try {
@@ -466,6 +480,7 @@ export class JSONPath {
         case '^=': outcome = `${v}`.startsWith(step.rval) === target; break;
         case '$=': outcome = `${v}`.endsWith(step.rval) === target; break;
         case '*=': outcome = `${v}`.includes(step.rval) === target; break;
+        case 're': outcome = step.rval.test(`${v}`); break;
         default: outcome = hasOwn === target; break;
         }
         if ( outcome ) { return k; }