From 2de285c04853a7554e014373c9ce38de452e46cf Mon Sep 17 00:00:00 2001
From: adarsh-priydarshi-5646 <adarshpriydarshi5646@gmail.com>
Date: Thu, 20 Nov 2025 11:47:19 +0530
Subject: [PATCH 1/2] feat: add isClosed() method to Deno.FsFile

Adds a new isClosed() method to check if a file has been closed.
This helps developers query the close status of FsFile instances.

Fixes #31341
---
 cli/tsc/dts/lib.deno.ns.d.ts | 11 +++++++++
 ext/fs/30_fs.js              | 10 ++++++++-
 tests/unit/files_test.ts     | 43 ++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/cli/tsc/dts/lib.deno.ns.d.ts b/cli/tsc/dts/lib.deno.ns.d.ts
index dae1c2cf2e0181..29d5f0668a12fc 100644
--- a/cli/tsc/dts/lib.deno.ns.d.ts
+++ b/cli/tsc/dts/lib.deno.ns.d.ts
@@ -2239,6 +2239,17 @@ declare namespace Deno {
      * ```
      */
     close(): void;
+    /**
+     * Check if the file is closed.
+     *
+     * ```ts
+     * const file = await Deno.open("my_file.txt");
+     * console.log(file.isClosed()); // false
+     * file.close();
+     * console.log(file.isClosed()); // true
+     * ```
+     */
+    isClosed(): boolean;
 
     [Symbol.dispose](): void;
   }
diff --git a/ext/fs/30_fs.js b/ext/fs/30_fs.js
index 16653592826edd..76d178de6bc1b7 100644
--- a/ext/fs/30_fs.js
+++ b/ext/fs/30_fs.js
@@ -584,6 +584,7 @@ class FsFile {
 
   #readable;
   #writable;
+  #closed = false;
 
   constructor(rid, symbol) {
     ObjectDefineProperty(this, internalRidSymbol, {
@@ -650,6 +651,11 @@ class FsFile {
 
   close() {
     core.close(this.#rid);
+    this.#closed = true;
+  }
+
+  isClosed() {
+    return this.#closed;
   }
 
   get readable() {
@@ -718,7 +724,9 @@ class FsFile {
   }
 
   [SymbolDispose]() {
-    core.tryClose(this.#rid);
+    if (core.tryClose(this.#rid)) {
+      this.#closed = true;
+    }
   }
 }
 
diff --git a/tests/unit/files_test.ts b/tests/unit/files_test.ts
index aa211b224d0bf9..7a8a94ca1a9134 100644
--- a/tests/unit/files_test.ts
+++ b/tests/unit/files_test.ts
@@ -701,6 +701,49 @@ Deno.test(
   },
 );
 
+Deno.test(
+  { permissions: { read: true } },
+  async function fsFileIsClosed() {
+    const file = await Deno.open("tests/testdata/assets/hello.txt");
+    assertEquals(file.isClosed(), false);
+    file.close();
+    assertEquals(file.isClosed(), true);
+  },
+);
+
+Deno.test(
+  { permissions: { read: true } },
+  function fsFileIsClosedSync() {
+    const file = Deno.openSync("tests/testdata/assets/hello.txt");
+    assertEquals(file.isClosed(), false);
+    file.close();
+    assertEquals(file.isClosed(), true);
+  },
+);
+
+Deno.test(
+  { permissions: { read: true } },
+  async function fsFileIsClosedWithUsing() {
+    let file2: Deno.FsFile;
+    {
+      using file = await Deno.open("tests/testdata/assets/hello.txt");
+      file2 = file;
+      assertEquals(file.isClosed(), false);
+    }
+    assertEquals(file2.isClosed(), true);
+  },
+);
+
+Deno.test(
+  { permissions: { read: true } },
+  async function fsFileIsClosedAfterManualCloseInUsing() {
+    using file = await Deno.open("tests/testdata/assets/hello.txt");
+    assertEquals(file.isClosed(), false);
+    file.close();
+    assertEquals(file.isClosed(), true);
+  },
+);
+
 Deno.test(
   { permissions: { read: true, write: true } },
   function fsFileDatasyncSyncSuccess() {

From 9344dc551d8224f354e28cdeb95394f4881f38b2 Mon Sep 17 00:00:00 2001
From: adarsh-priydarshi-5646 <adarshpriydarshi5646@gmail.com>
Date: Thu, 20 Nov 2025 12:09:14 +0530
Subject: [PATCH 2/2] fix: correct SymbolDispose implementation for isClosed

---
 ext/fs/30_fs.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/ext/fs/30_fs.js b/ext/fs/30_fs.js
index 76d178de6bc1b7..a0434b9bcdbc9a 100644
--- a/ext/fs/30_fs.js
+++ b/ext/fs/30_fs.js
@@ -724,9 +724,8 @@ class FsFile {
   }
 
   [SymbolDispose]() {
-    if (core.tryClose(this.#rid)) {
-      this.#closed = true;
-    }
+    core.tryClose(this.#rid);
+    this.#closed = true;
   }
 }