issue_comments: 512036050

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https://github.com/pydata/xarray/issues/2064#issuecomment-512036050 https://api.github.com/repos/pydata/xarray/issues/2064 512036050 MDEyOklzc3VlQ29tbWVudDUxMjAzNjA1MA== 1217238 2019-07-16T23:09:24Z 2019-07-16T23:09:24Z MEMBER

UPDATE: @shoyer it could be that unit tests are failing because, as your final example shows, you get an error for data_vars='minimal' if any variables have different values across datasets, when adding a new concatentation dimension. If this is the reason so many unit tests are failing, then the failures are a red herring and should probably be ignored/rewritten.

This seems very likely to me. The existing behavior of data_vars='minimal' is only useful in "existing dimensions mode".

Xarray's unit test suite is definitely a good "smoke test" for understanding the impact of changes to concat on our users. What it tells us is that we can't change the default value from "all" to "minimal" without breaking existing code. Instead, we need to change how "all" or "minimal" works, or switch to yet another mode for the new behavior.

The tests we should feel free to rewrite are cases where we set data_vars="all" or data_vars="minimal" explicitly for verifying the weird edge behaviors that I noted in my earlier comments. There shouldn't be too many of these tests.

 
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