push: fails with an HTTP external URL tracked by a .dvc file

[mdekstrand]

Bug Report

Description

I have a project that has external data files added with import-url. With the latest DVC (3.28), when I run dvc push, it fails with an unsupported operation in the HTTP remote:

Backtrace

2023-11-04 15:21:53,740 ERROR: unexpected error
Traceback (most recent call last):
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc/cli/__init__.py", line 209, in main
    ret = cmd.do_run()
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc/cli/command.py", line 26, in do_run
    return self.run()
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc/commands/data_sync.py", line 64, in run
    processed_files_count = self.repo.push(
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc/repo/__init__.py", line 61, in wrapper
    return f(repo, *args, **kwargs)
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc/repo/push.py", line 115, in push
    push_transferred, push_failed = ipush(
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc_data/index/push.py", line 59, in push
    old = build(data.path, data.fs)
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc_data/index/build.py", line 80, in build
    for entry in build_entries(path, fs, ignore=ignore):
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc_data/index/build.py", line 52, in build_entries
    walk_iter = fs.walk(path)
  File "/home/mde48/miniforge3/envs/lkpm/lib/python3.10/site-packages/dvc_http/__init__.py", line 153, in walk
    raise NotImplementedError
NotImplementedError

Reproduce

1. dvc init
2. dvc import-url https://files.grouplens.org/datasets/movielens/ml-latest-small.zip
3. dvc stage add -n extract -d ml-latest-small.zip -o ml-latest-small unzip ml-latest-small.zip
4. dvc repro
5. dvc remote add test ../test-remote
6. dvc push -r test

Expected

The cached outputs (and maybe a copy of the input, but I think that's a separate issue) to be pushed to the remote.

Environment information

Output of dvc doctor:

$ dvc doctor
DVC version: 3.28.0 (conda)
---------------------------
Platform: Python 3.10.13 on Linux-5.15.0-88-generic-x86_64-with-glibc2.35
Subprojects:
        dvc_data = 2.20.0
        dvc_objects = 1.1.0
        dvc_render = 0.6.0
        dvc_task = 0.3.0
        scmrepo = 1.4.1
Supports:
        http (aiohttp = 3.8.6, aiohttp-retry = 2.8.3),
        https (aiohttp = 3.8.6, aiohttp-retry = 2.8.3)
Config:
        Global: /home/mde48/.config/dvc
        System: /etc/xdg/dvc
Cache types: hardlink, symlink
Cache directory: ext4 on /dev/mapper/ubuntu--vg-ubuntu--lv
Caches: local
Remotes: local
Workspace directory: ext4 on /dev/mapper/ubuntu--vg-ubuntu--lv
Repo: dvc, git
Repo.site_cache_dir: /var/tmp/dvc/repo/45dbcc8b97aba74d36934a2f402ce97a

[dberenbaum]

Can confirm that I'm able to reproduce. Seems like this works fine in 3.27.0 and was introduced in 3.27.1. I'm guessing it's related to #9807 (cc @efiop).