From e006f023aaa628727f4cb7f7ab3d9261ccc92261 Mon Sep 17 00:00:00 2001
From: Liu Husong <ben@breeze.cash>
Date: Tue, 16 Dec 2025 21:52:38 +0800
Subject: [PATCH 1/2] adding a regression test

---
 dev/test/query.ts | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/dev/test/query.ts b/dev/test/query.ts
index b3ee1595b..c859e323d 100644
--- a/dev/test/query.ts
+++ b/dev/test/query.ts
@@ -1915,6 +1915,23 @@ describe('limit() interface', () => {
     query = query.limit(1).limit(2).limit(3);
     await query.get();
   });
+
+  // Regression test: This test currently fails because limit(0) is not
+  // serialized in the query proto (limit(0) is falsy in JavaScript).
+  // This test is expected to fail until the fix is applied.
+  it('handles limit(0) correctly', async () => {
+    const overrides: ApiOverride = {
+      runQuery: request => {
+        queryEquals(request, limit(0));
+        return emptyQueryStream();
+      },
+    };
+
+    firestore = await createInstance(overrides);
+    let query: Query = firestore.collection('collectionId');
+    query = query.limit(0);
+    await query.get();
+  });
 });
 
 describe('limitToLast() interface', () => {

From be8b9c59127373920af83cb14e7b810f17fdcb65 Mon Sep 17 00:00:00 2001
From: Liu Husong <ben@breeze.cash>
Date: Tue, 16 Dec 2025 21:53:05 +0800
Subject: [PATCH 2/2] fix: ensure limit(0) is properly serialized in query
 requests

Previously, calling `.limit(0)` on a Firestore Query did not correctly serialize the zero value to the underlying wire protocol. This caused queries intended to return zero results to be sent without a limit constraint, potentially returning unintended results.

This commit fixes the serialization logic so that `limit(0)` is now explicitly included in the query proto. Also adds/updates related unit tests to validate the correct handling of limit-zero queries.
---
 dev/src/reference/query-util.ts | 2 +-
 dev/src/reference/query.ts      | 2 +-
 dev/test/query.ts               | 3 ---
 3 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/dev/src/reference/query-util.ts b/dev/src/reference/query-util.ts
index c05e84b39..a5aa0c24f 100644
--- a/dev/src/reference/query-util.ts
+++ b/dev/src/reference/query-util.ts
@@ -344,7 +344,7 @@ export class QueryUtil<
                   // call to `requestStream()` will backoff should the restart
                   // fail before delivering any results.
                   let newQuery: Query<AppModelType, DbModelType>;
-                  if (!this._queryOptions.limit) {
+                  if (this._queryOptions.limit === undefined) {
                     newQuery = query;
                   } else {
                     const newLimit =
diff --git a/dev/src/reference/query.ts b/dev/src/reference/query.ts
index d3c383417..217095ad7 100644
--- a/dev/src/reference/query.ts
+++ b/dev/src/reference/query.ts
@@ -1439,7 +1439,7 @@ export class Query<
     structuredQuery.startAt = this.toCursor(this._queryOptions.startAt);
     structuredQuery.endAt = this.toCursor(this._queryOptions.endAt);
 
-    if (this._queryOptions.limit) {
+    if (this._queryOptions.limit !== undefined) {
       structuredQuery.limit = {value: this._queryOptions.limit};
     }
 
diff --git a/dev/test/query.ts b/dev/test/query.ts
index c859e323d..b11913ace 100644
--- a/dev/test/query.ts
+++ b/dev/test/query.ts
@@ -1916,9 +1916,6 @@ describe('limit() interface', () => {
     await query.get();
   });
 
-  // Regression test: This test currently fails because limit(0) is not
-  // serialized in the query proto (limit(0) is falsy in JavaScript).
-  // This test is expected to fail until the fix is applied.
   it('handles limit(0) correctly', async () => {
     const overrides: ApiOverride = {
       runQuery: request => {