List all Gentoo packages built against the old Lua or specific version

After similar articles about Python (List all Gentoo packages built against the old python or specific version) under Gentoo and Ruby List all Gentoo packages built against the old ruby or specific version, the Lua upgrade in Gentoo may have similar problems, so this article shows how to list old Lua modules and packages built against old Lua environments. Despite a clean upgrade without any blockers or masked packages, sometimes, on old machines, there might be packages left still built against an old version of Lua, which is even no longer available on the system!

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equery USE lua_targets_lua5-4

On Gentoo, there are two important flags in the configuration make.conf file:

LUA_TARGETS="lua5-1 lua5-4"

The LUA_TARGETS controls the support of multiple Lua versions installed on the system. When the Gentoo package has a use flag lua, the builder emerge will build the Lua module for all the Lua versions in LUA_TARGETS. Some programs or libraries may not support multiple versions to be installed on the system and they may require to specify just one Lua library target, against which they are going to be built and that’s why LUA_SINGLE_TARGET exists. In most cases, the LUA_SINGLE_TARGET should be the active (default in the system) Lua version.
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