[C++] Add operator== for interfaces with an Equals() method

[asfimport]

A common pattern in tests is ASSERT_TRUE(schm->Equals(*other). The addition of overloaded equality operators will allow this o be written ASSERT_EQ(*schm, *other), which is more idiomatic GTEST usage and will allow more informative assertion failure messages.

Reporter: Ben Kietzman / @bkietz
Assignee: Ben Harkins / @benibus

PRs and other links:

• GitHub Pull Request #14038

_{Note: This issue was originally created as ARROW-6772. Please see the migration documentation for further details.}

[asfimport]

Ben Kietzman / @bkietz:
operator== for Schemas was added by #5529

[asfimport]

Ben Kietzman / @bkietz:
Use the util::EqualityComparable mixin defined in #5621

At the same time it'd be useful to incorporate the util::ToStringOstreamable mixin (introduced in the same PR)

[asfimport]

Antoine Pitrou / @pitrou:
This still would need to be done for Field and DataType, at least.

[asfimport]

Todd Farmer / @toddfarmer:
This issue was last updated over 90 days ago, which may be an indication it is no longer being actively worked. To better reflect the current state, the issue is being unassigned. Please feel free to re-take assignment of the issue if it is being actively worked, or if you plan to start that work soon.

[asfimport]

Ben Harkins / @benibus:
I'm currently working on this one - planning on adding util::EqualityComparable to {}DataType{}, {}Field{}, and {}FieldRef{}. Should additional comparison tests be added (in addition to AssertXXXEqual) to type_test.cc or would that be considered redundant?

[asfimport]

Antoine Pitrou / @pitrou:
I think it would be nice to add at least basic tests to ensure that the operators properly redirect. No need to duplicate all tests though.

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 14038
#14038