The function gtest_discover_tests calls the passed test executable with
the parameter --gtest_list_tests and parses the output to find all
tests.
In case of value-parameterized tests ([1]), the test values are included
in the output. While test names are alphanumeric, the values can contain
arbitrary content.
First, the output is separated into lines with `foreach`. Included
semi-colons breaks this and need to get escaped.
Afterwards, the testname is passed on to the `add_command` helper. This
helper was converted into a macro in commit dac201442d (GoogleTest:
Optimize gtest_discover_tests, 2020-02-18). As a macro, its arguments
are re-evaluated. Therefore we need to escape `\`, `;` and to prevent
unwanted variable expansion `$`.
Fixes: #20661
[1] <https://github.com/google/googletest/blob/0eea2e9/googletest/docs/advanced.md#value-parameterized-tests>
Add a new gtest_discover_tests function to GoogleTest.cmake,
implementing dynamic test discovery (i.e. tests are discovered by
actually running the test executable and asking for the list of
available tests, which is used to dynamically declare the tests) rather
than the source-parsing approach used by gtest_add_tests. Compared to
the source-parsing approach, this has the advantage of being robust
against users declaring tests in unusual ways, and much better support
for advanced features such as parameterized tests.
A unit test, modeled after the TEST_INCLUDE_DIR[S] test, is also
included. Note that the unit test does not actually require that Google
Test is available. The new functionality does not actually depend on
Google Test as such; it only requires that the test executable lists
tests in the expected format when invoked with --gtest_list_tests, which
the unit test can fake readily.
