Previously, all targets were connected in one main target called
third-party in order to remove any potentially conflicting shared
library. We can make each dependency target independent of each other by
only removing shared libraries from luajit and msgpack in their own
targets, as only these has unwanted shared libraries.
59d5f692f removed cmake.deps/cmake/DownloadAndExtractFile.cmake and
support for USE_EXISTING_SRC_DIR. The Ubuntu nightly PPA still relies
on USE_EXISTING_SRC_DIR functionality since it can't access the network
during the build.
Supplying an empty value for ExternalProject_Add()'s URL value appears
to provide the needed mechanism to avoid re-downloading when the sources
are already present. This is undocumented behavior, though, so it may
break in the future.
Now, if USE_EXISTING_SRC_DIR is set, the ExternalProject's URL variable
is unset, preventing the download and erroring out if the source doesn't
actually exist.
DownloadAndExtractFile.cmake was initially introduced as a workaround to
avoid the massive amounts of logs generated by the download progress.
This is not a problem anymore as ExternalProject_Add has had the
DOWNLOAD_NO_PROGRESS option since cmake version 3.1.
Problem:
Dirs "config", "packaging", and "third-party" are all closely related
but this is not obvious from the layout. This adds friction for new
contributors.
Solution:
- rename config/ to cmake.config/
- rename test/config/ to test/cmakeconfig/ because it is used in Lua
tests: require('test.cmakeconfig.paths').
- rename packaging/ to cmake.packaging/
- rename third-party/ to cmake.deps/ (parallel with .deps/)
