corrade_add_test() on Emscripten clashes with CMAKE_CROSSCOMPILING_EMULATOR

[pezcode]

When CMAKE_CROSSCOMPILING_EMULATOR is set to the path to nodejs, corrade_add_test() finds and prepends nodejs a second time manually to add_test(). This leads to node trying to load its own binary and failing:

/emsdk/node/14.18.2_64bit/bin/node:1 ELF

 ^ SyntaxError: Invalid or unexpected token

Not sure what "the" correct solution is here. What came to my mind:

• Use CMAKE_CROSSCOMPILING_EMULATOR in Corrade's toolchain and remove the special handling from UseCorrade.cmake. Might break for some users who rarely update their toolchains.
• put the code in UseCorrade.cmake in between if(NOT CMAKE_CROSSCOMPILING_EMULATOR), a bit ugly but it should work

The official Emscripten toolchain file sets CMAKE_CROSSCOMPILING_EMULATOR, I think compatibility with it is fairly important. We've been using the Corrade toolchain, but the official one has a few advantages and works well these days, so we'd prefer to use that.

[mosra]

I think compatibility with it is fairly important

Yes.

but the official one has a few advantages and works well these days

:cry: Anything else I could add to mine, apart from the bloated load of automagic crap that's there?

remove the special handling from UseCorrade.cmake. Might break for some users who rarely update their toolchains.

I'm for this option. Toolchains breakage is fine, it breaks every second Emscripten update anyway. Plus, in many cases people are using a toolchain from within a Corrade submodule, so they get the update implicitly.

Additionally, if you're willing to make a PR for this, you could attempt to do the same treatment for the corrade-rc binary. It's been on my TODO list for a while, to not require an external build of it if CMAKE_CROSSCOMPILING_EMULATOR is set. Related is also https://github.com/mosra/corrade/issues/81.

[mosra]

Actually, I think the right solution is implementing both options. Especially in combination with corrade-rc being run through Node.js, which is anything but fast.

So, in particular:

• Add an if(NOT CMAKE_CROSSCOMPILING_EMULATOR) to UseCorrade.cmake so it still works with older toolchains, or when one explicitly disables that. For example, it should be possible to compile for Emscripten even without having that damn bloaty thing installed, and thus CMAKE_CROSSCOMPILING_EMULATOR may not be set at all.
• Then, make corrade-rc built and used if CMAKE_CROSSCOMPILING_EMULATOR is set and if CORRADE_RC_EXECUTABLE is not present (or it's not found). I.e., prefer the native version when possible, to not make #94 even worse than it is with large files.
• Then, make the toolchain attempt to find Node.js and set it as CMAKE_CROSSCOMPILING_EMULATOR if found. CMAKE_DISABLE_FIND_PACKAGE_NodeJs should work in this case and do the expected thing.