Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/4876
A quick post-mortem comment here:
This adds a lot of `equals()` and `hashCode()` on classes where these are
ill-defined.
For example: `StreamWriterBase` defines `equals()` and `hashCode()` just on
a subset of configuration fields (here the sync field) and ignore the
associated stream, because equals and hash is ill-defined on the stream. To me,
the correct conclusion is that `equals()` and `hashCode()` are ill-defined on
`StreamWriterBase` and should not be there!
Adding such methods just to make assertion statement in tests more compact
wrongly pushes some specific test logic in to the main classes. The correct way
is to adjust the assertions in the test, or, if there is a lot of repetitive
checking, create a `Matcher` that matches "equality based on some fields" and
replace `assertEquals(X, Y)` with `assertThat(matcher, X, Y)`.
I think in this case, it is actually a reason for a follow-up patch that
changes this.
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