fix(serde_v8): no panic on reading large text file (#15494)

Co-authored-by: Nayeem Rahman <nayeemrmn99@gmail.com>

cli/tests/unit/read_text_file_test.ts

@@ -145,3 +145,45 @@ Deno.test(
     assert(data.length > 0);
   },
 );
+
+Deno.test(
+  { permissions: { read: true, write: true } },
+  function readTextFileSyncV8LimitError() {
+    const kStringMaxLengthPlusOne = 536870888 + 1;
+    const bytes = new Uint8Array(kStringMaxLengthPlusOne);
+    const filePath = "cli/tests/testdata/too_big_a_file.txt";
+
+    Deno.writeFileSync(filePath, bytes);
+
+    assertThrows(
+      () => {
+        Deno.readTextFileSync(filePath);
+      },
+      TypeError,
+      "buffer exceeds maximum length",
+    );
+
+    Deno.removeSync(filePath);
+  },
+);
+
+Deno.test(
+  { permissions: { read: true, write: true } },
+  async function readTextFileV8LimitError() {
+    const kStringMaxLengthPlusOne = 536870888 + 1;
+    const bytes = new Uint8Array(kStringMaxLengthPlusOne);
+    const filePath = "cli/tests/testdata/too_big_a_file_2.txt";
+
+    await Deno.writeFile(filePath, bytes);
+
+    await assertRejects(
+      async () => {
+        await Deno.readTextFile(filePath);
+      },
+      TypeError,
+      "buffer exceeds maximum length",
+    );
+
+    await Deno.remove(filePath);
+  },
+);

core/runtime.rs

@@ -1946,7 +1946,12 @@ impl JsRuntime {
 
       for (promise_id, mut resp) in results.into_iter() {
         args.push(v8::Integer::new(scope, promise_id).into());
-        args.push(resp.to_v8(scope).unwrap());
+        args.push(match resp.to_v8(scope) {
+          Ok(v) => v,
+          Err(e) => OpResult::Err(OpError::new(&|_| "TypeError", e.into()))
+            .to_v8(scope)
+            .unwrap(),
+        });
       }
 
       let tc_scope = &mut v8::TryCatch::new(scope);

serde_v8/ser.rs

@@ -447,11 +447,16 @@ impl<'a, 'b, 'c> ser::Serializer for Serializer<'a, 'b, 'c> {
   }
 
   fn serialize_str(self, v: &str) -> JsResult<'a> {
-    Ok(
-      v8::String::new(&mut self.scope.borrow_mut(), v)
-        .unwrap()
-        .into(),
-    )
+    let maybe_str = v8::String::new(&mut self.scope.borrow_mut(), v);
+
+    // v8 string can return 'None' if buffer length > kMaxLength.
+    if let Some(str) = maybe_str {
+      Ok(str.into())
+    } else {
+      Err(Error::Message(String::from(
+        "Cannot allocate String: buffer exceeds maximum length.",
+      )))
+    }
   }
 
   fn serialize_bytes(self, v: &[u8]) -> JsResult<'a> {