I had this after reading #12537 and #9047. Currently `DockerOperator`’s `volumes` argument is passed directly to docker-py’s `bind` (aka `docker -v`). But `-v`’s behaviour has long been problematic, and [Docker has been pushing users to the new `--mount` syntax instead](https://docs.docker.com/storage/bind-mounts/#choose-the--v-or---mount-flag). With #12537, it seems like `-v`’s behaviour is also confusing to some Airflow users, so I want to migrate Airflow’s internals to `--mount`.

However, `--mount` has a different syntax to `-v`, and the behaviour is also slightly different, so for compatibility reasons we can’t just do it under the hood. I can think of two possible solutions to this:

A. Deprecate `volumes` altogether and introduce `DockerOperator(mounts=...)`

This will emit a deprecation warning when the user passes `DockerOperator(volumes=...)` to tell them to convert to `DockerOperator(mounts=...)` instead. `volumes` will stay unchanged otherwise, and continue to be passed to bind mounts.

`mounts` will take a list of [`docker.types.Mount`](https://docker-py.readthedocs.io/en/stable/api.html#docker.types.Mount) to describe the mounts. They will be passed directly to the mounts API. Some shorthands could be useful as well, for example:

```python
DockerOperator(
    ...
    mounts=[
        ('/root/data1', './data1'),  # Source and target, default to volume mount.
        ('/root/data2', './data2', 'bind'),  # Bind mount.
    ],
)
```

B. Reuse `volumes` and do introspection to choose between binds and mounts

The `volumes` argument can be augmented to also accept `docker.types.Mount` instances, and internally we’ll do something like

```python
binds = []
mounts = []
for vol in volumes:
    if isinstance(vol, str):
        binds.append(vol)
    elif isintance(vol, docker.types.Mount):
        mounts.append(vol)
    else:
        raise ValueError('...')
if binds:
    warnings.warn('...', DeprecationWarning)
```

and pass the collected lists to binds and mounts respectively.

I’m very interested in hearing thoughts on this.


**Are you willing to submit a PR?**
Yes

**Related Issues**

* #12537: Confusing on the bind syntax.
* #9047: Implement mounting in `DockerSwarmOperator` (it’s a subclass of `DockerOperator`, but the `volumes` option is currently unused).

docs/conf.py
# If this is True, viewcode extension will emit viewcode-follow-imported event to resolve the name of
# the module by other extensions. The default is True.
viewcode_follow_imported_members = True
# -- Options for sphinx-autoapi ------------------------------------------------
# 
# Paths (relative or absolute) to the source code that you wish to generate
# your API documentation from.
autoapi_dirs = [
    PACKAGE_DIR,
]
# A directory that has user-defined templates to override our default templates.
if PACKAGE_NAME == 'apache-airflow':
    autoapi_template_dir = 'autoapi_templates'
# A list of patterns to ignore when finding files
autoapi_ignore = [
    'airflow/configuration/',
    '*/example_dags/*',
    '*/_internal*',
    '*/node_modules/*',
    '*/migrations/*',
    '*/contrib/*',
]
if PACKAGE_NAME == 'apache-airflow':
    autoapi_ignore.append('*/airflow/providers/*')
# Keep the AutoAPI generated files on the filesystem after the run.
# Useful for debugging.
autoapi_keep_files = True
# Relative path to output the AutoAPI files into. This can also be used to place the generated documentation
# anywhere in your documentation hierarchy.
autoapi_root = '_api'