FSA: Make WPTs assert that overwriting file moves are allowed

This codifies the behavior agreed upon here:
whatwg/fs#10 (comment)

See go/fsa-overwriting-moves for more context

Bug: 1366652, 1381621
Change-Id: I24d8ff94ebd9f6b6a8f2ffe9a0e30623193e7eab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4076968
Auto-Submit: Austin Sullivan <asully@chromium.org>
Reviewed-by: Daseul Lee <dslee@chromium.org>
Commit-Queue: Daseul Lee <dslee@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1079294}

fs/script-tests/FileSystemFileHandle-move.js

@@ -94,14 +94,21 @@ directory_test(async (t, root) => {
   await promise_rejects_dom(
       t, 'NoModificationAllowedError', handle.move('file-after'));
 
-  // Can't move handle to overwrite an existing file.
   await stream.close();
-  await promise_rejects_dom(
-      t, 'InvalidModificationError', handle.move('file-after'));
   assert_array_equals(
       await getSortedDirectoryEntries(root), ['file-after', 'file-before']);
 }, 'move(name) while the destination file has an open writable fails');
 
+directory_test(async (t, root) => {
+  const handle = await createFileWithContents(t, 'file-before', 'abc', root);
+  const handle_dest =
+      await createFileWithContents(t, 'file-after', '123', root);
+
+  await handle.move('file-after');
+  assert_array_equals(await getSortedDirectoryEntries(root), ['file-after']);
+  assert_equals(await getFileContents(handle), 'abc');
+  assert_equals(await getFileContents(handle_dest), 'abc');
+}, 'move(name) can overwrite an existing file');
 
 directory_test(async (t, root) => {
   const handle = await createFileWithContents(t, 'file-before', 'foo', root);
@@ -290,13 +297,23 @@ directory_test(async (t, root) => {
   // Assert the file is still in the source directory.
   assert_array_equals(await getSortedDirectoryEntries(dir_src), ['file']);
 
-  // Can't move handle to overwrite an existing file.
   await stream.close();
-  await promise_rejects_dom(
-      t, 'InvalidModificationError', file.move(dir_dest));
-  assert_array_equals(await getSortedDirectoryEntries(dir_src), ['file']);
+  assert_array_equals(await getSortedDirectoryEntries(dir_dest), ['file']);
 }, 'move(dir) while the destination file has an open writable fails');
 
+directory_test(async (t, root) => {
+  const dir_src = await root.getDirectoryHandle('dir-src', {create: true});
+  const dir_dest = await root.getDirectoryHandle('dir-dest', {create: true});
+  const file = await createFileWithContents(t, 'file', 'abc', dir_src);
+  const file_dest = await createFileWithContents(t, 'file', '123', dir_dest);
+
+  await file.move(dir_dest);
+  assert_array_equals(await getSortedDirectoryEntries(dir_src), []);
+  assert_array_equals(await getSortedDirectoryEntries(dir_dest), ['file']);
+  assert_equals(await getFileContents(file), 'abc');
+  assert_equals(await getFileContents(file_dest), 'abc');
+}, 'move(dir) can overwrite an existing file');
+
 directory_test(async (t, root) => {
   const dir_src = await root.getDirectoryHandle('dir-src', {create: true});
   const dir_dest = await root.getDirectoryHandle('dir-dest', {create: true});
@@ -314,12 +331,22 @@ directory_test(async (t, root) => {
   // Assert the file is still in the source directory.
   assert_array_equals(await getSortedDirectoryEntries(dir_src), ['file-src']);
 
-  // Can't move handle to overwrite an existing file.
   await stream.close();
-  await promise_rejects_dom(
-      t, 'InvalidModificationError', file.move(dir_dest, 'file-dest'));
-  // Assert the file is still in the source directory.
-  assert_array_equals(await getSortedDirectoryEntries(dir_src), ['file-src']);
-  assert_equals(await getFileContents(file), 'abc');
-  assert_equals(await getFileSize(file), 3);
+  assert_array_equals(await getSortedDirectoryEntries(dir_dest), ['file-dest']);
 }, 'move(dir, name) while the destination file has an open writable fails');
+
+directory_test(async (t, root) => {
+  const dir_src = await root.getDirectoryHandle('dir-src', {create: true});
+  const dir_dest = await root.getDirectoryHandle('dir-dest', {create: true});
+  const file = await createFileWithContents(t, 'file-src', 'abc', dir_src);
+  const file_dest =
+      await createFileWithContents(t, 'file-dest', '123', dir_dest);
+
+  await file.move(dir_dest, 'file-dest');
+
+  // Assert the file has been moved to the destination directory and renamed.
+  assert_array_equals(await getSortedDirectoryEntries(dir_src), []);
+  assert_array_equals(await getSortedDirectoryEntries(dir_dest), ['file-dest']);
+  assert_equals(await getFileContents(file), 'abc');
+  assert_equals(await getFileContents(file_dest), 'abc');
+}, 'move(dir, name) can overwrite an existing file');