It doesn't really work for tests that depend on more than one plugin
(because there i would need to handle all combinations, somehow), but it
does the job when the end user has such use case.
This makes it possible to:
- finally use Magnum as a CMake subproject on Windows and have your
executables not fail to run with a "DLL missing" error (and the
setting is put to cache so superprojects just implicitly make use of
that)
- run tests on Windows without having to install first
- use dynamic plugins from a CMake subproject on any platform without
having to install first or load them by filename --- and the plugin
directory is now easily discovered as relative to
libraryLocation() of the library implementing given plugin interface
The current testing workflow had quite a few major flaws and it was no
longer possible after the move of Any* plugins to core. Among the flaws
is:
* Every plugin was basically built twice, once as the real plugin and
once as a static testing library. Most of the build shared common
object files, but nevertheless it inflated build times and made the
buildsystem extremely complex.
* Because the actual plugin binary was never actually loaded during the
test, it couldn't spot problems like:
- undefined references
- errors in metadata files
- mismatched plugin interface/version, missing entry points
- broken static plugin import files
* Tests that made use of independent plugins (such as TgaImageConverter
test using TgaImporter to verify the output) had a hardcoded
dependency on such plugins, making a minimal setup very hard.
* Dynamic loading of plugins from the Any* proxies was always directed
to the install location on the filesystem with no possibility to
load these directly from the build tree. That caused random ABI
mismatch crashes, or, on the other hand, if no plugins were
installed, particular portions of the codebase weren't tested at all.
Now the workflow is the following:
* Every plugin is built exactly once, either as dynamic or as static.
* The test always loads it via the plugin manager. If it's dynamic,
it's loaded straight from the build directory; if it's static, it
gets linked to the test executable directly.
* Plugins used indirectly are always served from the build directory
(if enabled) to ensure reproducibility and independence on what's
installed on the filesystem. Missing presence of these plugins causes
particular tests to be simply skipped.
* Plugins that have extensive tests for internal functionality that's
not exposed through the plugin interface are still built in two
parts, but the internal tests are simply consuming the OBJECT files
directly instead of linking to a static library.
Statically built plugins get imported automatically when using CMake 3.1
and newer. Otherwise simply #include a corresponding
importStaticPlugin.cpp file.
Please note that this is not exactly backwards compatible, but as most
uses of the plugin library are without interacting with CMake, it
shouldn't be as painful, hopefully. In any case, recreate the build dir
and update your copy of Find*.cmake modules to avoid weird things
happening.
User-facing changes:
* Documentation of Find*.cmake modules converted to reStructuredText to
follow official CMake guidelines.
* The newfangled way to link the plugins is to use
MagnumPlugins::JpegImporter instead of
${MAGNUMPLUGINS_JPEGIMPORTER_LIBRARIES} and
${MAGNUMPLUGINS_JPEGIMPORTER_INCLUDE_DIRS}.
* The old ${MAGNUMPLUGINS_*_LIBRARIES} are deprecated and
just expand to MagnumPlugins::* target and are exposed only if
building with BUILD_DEPRECATED.
* The old ${MAGNUMPLUGINS_*_INCLUDE_DIRS} are removed, as the
MagnumPlugins::* targets cover that now as well.
Internal changes:
* Removed global state in favor of target-specific settings.
Vladimír Vondruš