5 files changed, 107 insertions, 0 deletions

diff --git a/cli/js/deno_unstable.ts b/cli/js/deno_unstable.ts
index 967eafdcd..2327b554d 100644
--- a/cli/js/deno_unstable.ts
+++ b/cli/js/deno_unstable.ts
@@ -4,6 +4,7 @@
 
 export { umask } from "./ops/fs/umask.ts";
 export { linkSync, link } from "./ops/fs/link.ts";
+export { fstatSync, fstat } from "./ops/fs/stat.ts";
 export { fsyncSync, fsync } from "./ops/fs/sync.ts";
 export { symlinkSync, symlink } from "./ops/fs/symlink.ts";
 export { loadavg, osRelease, hostname } from "./ops/os.ts";
diff --git a/cli/js/lib.deno.unstable.d.ts b/cli/js/lib.deno.unstable.d.ts
index daecf6604..cc7dea987 100644
--- a/cli/js/lib.deno.unstable.d.ts
+++ b/cli/js/lib.deno.unstable.d.ts
@@ -1142,4 +1142,26 @@ declare namespace Deno {
    * ```
    */
   export function fsync(rid: number): Promise<void>;
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   * Synchronously returns a `Deno.FileInfo` for the given file stream.
+   *
+   * ```ts
+   * const file = Deno.openSync("file.txt", { read: true });
+   * const fileInfo = Deno.fstatSync(file.rid);
+   * assert(fileInfo.isFile);
+   * ```
+   */
+  export function fstatSync(rid: number): FileInfo;
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   * Returns a `Deno.FileInfo` for the given file stream.
+   *
+   * ```ts
+   * const file = await Deno.open("file.txt", { read: true });
+   * const fileInfo = await Deno.fstat(file.rid);
+   * assert(fileInfo.isFile);
+   * ```
+   */
+  export function fstat(rid: number): Promise<FileInfo>;
 }
diff --git a/cli/js/ops/fs/stat.ts b/cli/js/ops/fs/stat.ts
index 93d31fc3f..402adeafc 100644
--- a/cli/js/ops/fs/stat.ts
+++ b/cli/js/ops/fs/stat.ts
@@ -66,6 +66,14 @@ export function parseFileInfo(response: StatResponse): FileInfo {
   };
 }
 
+export function fstatSync(rid: number): FileInfo {
+  return parseFileInfo(sendSync("op_fstat", { rid }));
+}
+
+export async function fstat(rid: number): Promise<FileInfo> {
+  return parseFileInfo(await sendAsync("op_fstat", { rid }));
+}
+
 export async function lstat(path: string | URL): Promise<FileInfo> {
   path = pathFromURL(path);
   const res = (await sendAsync("op_stat", {
diff --git a/cli/ops/fs.rs b/cli/ops/fs.rs
index 9417c112d..7c8100605 100644
--- a/cli/ops/fs.rs
+++ b/cli/ops/fs.rs
@@ -23,6 +23,7 @@ pub fn init(i: &mut CoreIsolate, s: &State) {
   i.register_op("op_open", s.stateful_json_op2(op_open));
   i.register_op("op_seek", s.stateful_json_op2(op_seek));
   i.register_op("op_fsync", s.stateful_json_op2(op_fsync));
+  i.register_op("op_fstat", s.stateful_json_op2(op_fstat));
   i.register_op("op_umask", s.stateful_json_op(op_umask));
   i.register_op("op_chdir", s.stateful_json_op(op_chdir));
   i.register_op("op_mkdir", s.stateful_json_op(op_mkdir));
@@ -251,6 +252,51 @@ fn op_fsync(
 }
 
 #[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct FstatArgs {
+  promise_id: Option<u64>,
+  rid: i32,
+}
+
+fn op_fstat(
+  isolate_state: &mut CoreIsolateState,
+  state: &State,
+  args: Value,
+  _zero_copy: &mut [ZeroCopyBuf],
+) -> Result<JsonOp, OpError> {
+  state.check_unstable("Deno.fstat");
+  let args: FstatArgs = serde_json::from_value(args)?;
+  let rid = args.rid as u32;
+
+  let resource_table = isolate_state.resource_table.clone();
+  let is_sync = args.promise_id.is_none();
+
+  if is_sync {
+    let mut resource_table = resource_table.borrow_mut();
+    let metadata = std_file_resource(&mut resource_table, rid, |r| match r {
+      Ok(std_file) => std_file.metadata().map_err(OpError::from),
+      Err(_) => Err(OpError::type_error(
+        "cannot stat this type of resource".to_string(),
+      )),
+    })?;
+    Ok(JsonOp::Sync(get_stat_json(metadata).unwrap()))
+  } else {
+    let fut = async move {
+      let mut resource_table = resource_table.borrow_mut();
+      let metadata =
+        std_file_resource(&mut resource_table, rid, |r| match r {
+          Ok(std_file) => std_file.metadata().map_err(OpError::from),
+          Err(_) => Err(OpError::type_error(
+            "cannot stat this type of resource".to_string(),
+          )),
+        })?;
+      Ok(get_stat_json(metadata).unwrap())
+    };
+    Ok(JsonOp::Async(fut.boxed_local()))
+  }
+}
+
+#[derive(Deserialize)]
 struct UmaskArgs {
   mask: Option<u32>,
 }
diff --git a/cli/tests/unit/stat_test.ts b/cli/tests/unit/stat_test.ts
index 67598a2d7..b32949286 100644
--- a/cli/tests/unit/stat_test.ts
+++ b/cli/tests/unit/stat_test.ts
@@ -6,6 +6,36 @@ import {
   pathToAbsoluteFileUrl,
 } from "./test_util.ts";
 
+unitTest({ perms: { read: true } }, function fstatSyncSuccess(): void {
+  const file = Deno.openSync("README.md");
+  const fileInfo = Deno.fstatSync(file.rid);
+  assert(fileInfo.isFile);
+  assert(!fileInfo.isSymlink);
+  assert(!fileInfo.isDirectory);
+  assert(fileInfo.size);
+  assert(fileInfo.atime);
+  assert(fileInfo.mtime);
+  assert(fileInfo.birthtime);
+
+  Deno.close(file.rid);
+});
+
+unitTest({ perms: { read: true } }, async function fstatSuccess(): Promise<
+  void
+> {
+  const file = await Deno.open("README.md");
+  const fileInfo = await Deno.fstat(file.rid);
+  assert(fileInfo.isFile);
+  assert(!fileInfo.isSymlink);
+  assert(!fileInfo.isDirectory);
+  assert(fileInfo.size);
+  assert(fileInfo.atime);
+  assert(fileInfo.mtime);
+  assert(fileInfo.birthtime);
+
+  Deno.close(file.rid);
+});
+
 unitTest(
   { perms: { read: true, write: true } },
   function statSyncSuccess(): void {