[FR]: `EXPECT_NONFATAL_FAILURE` and friends: Support multiple (variadic) substrings

[MikeWeller]

I would like to be able to pass multiple substrings to EXPECT_NONFATAL_FAILURE so that all the substrings must appear in the failure output.

This should I guess also apply to the other EXPECT_(FATAL|NONFATAL)_FAILURE[_ON_ALL_THREADS].

Does the feature exist in the most recent commit?

No

Why do we need this feature?

When testing matchers that produce detailed output (e.g. multi-line, or printing details from inner/nested matchers), it's brittle and cumbersome to test either one big string (where the test now depends on unimportant indentation/formatting), or have to repeat the entire EXPECT_NONFATAL_FAILURE multiple times to verify multiple substrings.

Describe the proposal.

For my use case, I want to be able to do something like:

        EXPECT_NONFATAL_FAILURE(
               [&] {
                   EXPECT_THAT(myObject, MyMatcher(...));
               }(),
               "Substring 1",
               "Substring 2");

I haven't looked at whether this can be done in a backward compatible way using __VA_ARGS__/__VA_OPT__/etc.

Is the feature specific to an operating system, compiler, or build system version?

No.