fix(services/dropbox): fix dropbox ci

[zjregee]

fix: #4484

There are several issues that need to be fixed here, related ci: https://github.com/apache/opendal/actions/runs/8682043318/job/23805843756.

Error caused by Dropbox service not supporting:

• test_copy_overwrite
• test_copy_file_with_non_ascii_name
• test_rename_overwrite
• test_list_prefix
• test_list_file_with_recursive

Should return an error when it does not exist:

• test_copy_non_existing_source
• test_rename_non_existing_source

Returned by list does not contact the complete path:

• test_list_dir
• test_list_dir_with_metakey
• test_list_dir_with_metakey_complete
• test_list_rich_dir
• test_list_nested_dir
• test_list_dir_with_recursive
• test_list_dir_with_recursive_no_trailing_slash

List dir should only return dir/

• test_list_empty_dir
• test_list_dir_with_file_path

[Xuanwo]

It doesn't make sense. All services that implement list_dir should have list prefix.

[zjregee]

I'm not sure about this, I don't see it described in the API documentation, and in my practice Dropbox doesn't implement prefix matching.

[Xuanwo]

prefix matching is simulated at

opendal/core/src/layers/complete.rs

Lines 276 to 322 in 755de58

	async fn complete_list(
	&self,
	path: &str,
	args: OpList,
	) -> Result<(RpList, CompleteLister<A, A::Lister>)> {
	let cap = self.meta.full_capability();
	if !cap.list {
	return Err(self.new_unsupported_error(Operation::List));
	}
	let recursive = args.recursive();
	match (recursive, cap.list_with_recursive) {
	// - If service can list_with_recursive, we can forward list to it directly.
	(_, true) => {
	let (rp, p) = self.inner.list(path, args).await?;
	Ok((rp, CompleteLister::One(p)))
	}
	// If recursive is true but service can't list_with_recursive
	(true, false) => {
	// Forward path that ends with /
	if path.ends_with('/') {
	let p = FlatLister::new(self.inner.clone(), path);
	Ok((RpList::default(), CompleteLister::Two(p)))
	} else {
	let parent = get_parent(path);
	let p = FlatLister::new(self.inner.clone(), parent);
	let p = PrefixLister::new(p, path);
	Ok((RpList::default(), CompleteLister::Four(p)))
	}
	}
	// If recursive and service doesn't support list_with_recursive, we need to handle
	// list prefix by ourselves.
	(false, false) => {
	// Forward path that ends with /
	if path.ends_with('/') {
	let (rp, p) = self.inner.list(path, args).await?;
	Ok((rp, CompleteLister::One(p)))
	} else {
	let parent = get_parent(path);
	let (rp, p) = self.inner.list(parent, args).await?;
	let p = PrefixLister::new(p, path);
	Ok((rp, CompleteLister::Three(p)))
	}
	}
	}
	}

I have a plan to refactor them later to make those behavior more clear.

[Xuanwo]

We can remove existing file before rename/copy.

[zjregee]

Updated.