[FR]: Matcher for absl::StatusOr and std::expected about googletest HOT 6 OPEN

Interestingly enough, Optional() can be used.

enum class Error { boom };

std::expected<int, Error> something = 1;
EXPECT_THAT(something, testing::Optional(testing::Gt(0)));

std::expected<int, Error> something = std::unexpected(Error::boom);
EXPECT_EQ(something, std::unexpected(Error::boom));

from googletest.

Interestingly enough, Optional() can be used.

enum class Error { boom };

std::expected<int, Error> something = 1;
EXPECT_THAT(something, testing::Optional(testing::Gt(0)));

std::expected<int, Error> something = std::unexpected(Error::boom);
EXPECT_EQ(something, std::unexpected(Error::boom));

Thats weird, still believe there should be a dedicated macro

from googletest.

Thats weird, still believe there should be a dedicated macro

I agree, the Optional thing is a hacky workaround for now but I would want something like EXPECT_THAT(something, testing::Expected(some_val)) where DescribeNegationTo would indicate that either there was a failure (and describe the error object, if possible) or that it succeeded with an unexpected value.

For a more fluent approach, maybe there could be matchers like EXPECT_THAT(something, succeedsWith(successValMatcher)) or EXPECT_THAT(something, failsWith(errorValMatcher))

Similar to how the existing matchers for Optional and Variant are quite general (ie not bound to the std:: classes), I think it should be reasonable to write this matcher with sufficient generality to work with std::expected and other popular value-or-error types. See e.g., https://ned14.github.io/outcome/tutorial/advanced/interop/value-or-error/

We can assume

• value()
• error()
• has_value()

and public typedefs value_type and error_type. I don't think we need to do any ADL free function stuff like with variant.

This should work with std::expected, TartanLlama tl::expected, Boost.Outcome outcome::result, Boost.System system::result etc

from googletest.

The matcher for absl::StatusOr will be released by the abseil-cpp project. Someone is working on it now, but it will take a while.

C++23 and std::expected is not supported yet. We do not want it implemented until C++23 is officially supported.

from googletest.

In case it gets approved, assign it to me

from googletest.

For a more fluent approach, maybe there could be matchers like EXPECT_THAT(something, succeedsWith(successValMatcher)) or EXPECT_THAT(something, failsWith(errorValMatcher))

I like this.
It's a little bit weird cuz absl version std::expected is StatusOr, there should be matcher name that will be understood by both library users.
Having it testing::Expected makes it a bit harder to read because of the EXPECTED_X macros.

from googletest.