id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
773048869,MDExOlB1bGxSZXF1ZXN0NTQ0MjA3MjE0,4721,APIv2 internal cleanups,226037,closed,0,,,1,2020-12-22T15:52:28Z,2020-12-22T16:47:10Z,2020-12-22T16:47:10Z,MEMBER,,0,pydata/xarray/pulls/4721," - [x] Related to #4309 
 - [x] No tests added, all tests pass
 - [x] Passes `isort . && black . && mypy . && flake8`
 - [x] No user visible change
 - [x] No new functions/methods

Stop importing `api.py` in `apiv2.py` and other internal cleanups.

This is needed by another change that results in a cyclic import due to `api`.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4721/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
771048648,MDExOlB1bGxSZXF1ZXN0NTQyNjc2MDQ4,4709,APIv2: move all _autodetect_engine logic to the plugins,226037,closed,0,,,0,2020-12-18T17:23:16Z,2020-12-22T15:33:40Z,2020-12-22T15:33:40Z,MEMBER,,0,pydata/xarray/pulls/4709," - [x] Relates to #4309 
 - [x] Tests updated
 - [x] Passes `isort . && black . && mypy . && flake8`
 - No user visible changes (including notable bug fixes) are documented in `whats-new.rst`
 - No new functions/methods are listed in `api.rst`

**Changes affects only APIv2.**

This PR removes all remaining knowledge about what backend support from the generic code path in `apiv2.open_dataset`.

Once we make the switch to API v2 a big chunk of code can be removed from `api.py`.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4709/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
770801513,MDExOlB1bGxSZXF1ZXN0NTQyNDc3NDg0,4707,APIv2: pass user defined `filename_or_obj` to backends as is,226037,closed,0,,,1,2020-12-18T11:14:05Z,2020-12-22T14:14:18Z,2020-12-22T14:14:18Z,MEMBER,,0,pydata/xarray/pulls/4707," - [x] Related to #4309
 - No test added, but all tests pass.
 - [x] Passes `isort . && black . && mypy . && flake8`
 - [x] User visible changes (including notable bug fixes) are documented in `whats-new.rst`
 - No new functions/methods.

**The change affects only APIv2.**

Pros:
- `open_dataset` passes the dataset description object `filename_or_obj` to the backends without fiddling with it. This is more and more important as several backends know how to open `dict`s, `file`'s `str`s that are not paths (*rasterio* for example accepts GDAL strings that are not paths and that is one of the reasons `engine=""rasterio""` cannot be used in `open_dataset`)

Cons:
- at the moment backends expect paths to always be absolute, not sure if they use this info.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4707/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull