This opens the door for replacing all `library ...` lines in toolchain
test files with `library "[[@TEST_NAME]]";`. That's technically more
typing in a lot of cases, but OTOH means we can just do some copy-paste
boilerplate and stop carefully writing library names.
Also cleans up the test setup, because it's getting messy. I'm trying to
make it easier to see the divisions of tests and the output associated
with them. StringSwitch looked like a way to do this, with a few edits
to make it work nicely.
This has is a nice-to-have for me. Frequently I want to run a specific
test, and end up digging through output to be able to copy-paste the run
line. This uses TIP lines to inject the command into the file when using
AUTOUPDATE.
Note, one of the reasons I want this is because "bazel test
//toolchain/testing:file_test --test_output=all" has been regularly
exceeding bazel's output limit for me (workaround is either opening the
output file or specifying an obscure output limit flag), making it a
little harder for me to get the commands. However, frequently I'm adding
a file and want to iterate on it, so that's really the use case I have
in mind here.
Write unattached CHECK:STDOUT lines at the end of the complete test
file, not at the end of the first split file.
Also, perform line number remappings for the current file even if we see
a check line for an earlier file first. We used to stop performing
remapping after the first check line that referred to a previous file.
To facilitate this, instead of splitting the check lines up by output
file prior to forming the output, we instead form a single list of check
lines and have the check lines track which file they refer to.