Address relocatable package installs and usage of <Package>Config.cmake files

[bartlettroscoe]

Parent Issue:

• EPIC: Merge TriBITS concepts and implementation of Packages and TPLs #63

Description

As mentioned in #63 (comment) and discussed in more detail in CMake Issue #24378 there is a problem with building, packaging, and installing from a binary package, and then downstream CMake projects using the installed CMake packages using find_package(<Package>). The problem is that the <Package>Config.cmake files will not easily know where to find their upstream dependencies.

Proposed implementation

The proposed solution to this problem discussed in CMake Issue #24378 comment is outlined below:

• Add new var <Project>_SUPER_INSTALL_PREFIX (in addition to <Project>_SET_GROUP_AND_PERMISSIONS_ON_INSTALL_BASE_DIR as they have different purposes) ...

• Have TriBITS-generated <Package>Config.cmake files use set(<ExternalPackage>_DIR "???") and find_dependency(<ExternalPackage>) (where <ExternalPackage>_DIR is either set to a relative or absolute path as described below).

• Add new var <ExternalPackage>_USE_RELATIVE_PATH:

  • If <ExternalPackage>_USE_RELATIVE_PATH is empty, then set to TRUE if <ExternalPackage>_DIR returned from find_package(<ExternalPackage>) (or <Package>_TRIBITS_COMPLIANT_PACKAGE_CONFIG_FILE_DIR if <ExternalPackage>_DIR is not set) is a subdir of <Project>_SUPER_INSTALL_PREFIX

  • If <ExternalPackage>_USE_RELATIVE_PATH is TRUE, then use a relative path from the TriBITS-generated installed <Package>Config.cmake file to <ExternalPackage>_DIR (or <Package>_TRIBITS_COMPLIANT_PACKAGE_CONFIG_FILE_DIR if <ExternalPackage>_DIR is not set)

  • If <ExternalPackage>_USE_RELATIVE_PATH is FALSE, then use the absolute path to <ExternalPackage>_DIR (or <Package>_TRIBITS_COMPLIANT_PACKAGE_CONFIG_FILE_DIR if <ExternalPackage>_DIR is not set)

• Change TriBITS-generated <Package>Config.cmake files to call find_dependency(<ExternalPackage> CONFIG REQUIRED) on all upstream dependencies and find a way for that to not interfere with inner find_dependency(<ExternalPackage) calls that find non-TriBITS-compliant external packages. (Idea: pass in TRIBITS_COMPLIANT as the version to find_package() or find_dependency() and make the TriBITS-generated <ExternalPackage>ConfigVersion.cmake file look for that instead of the current hack based on the variable TRIBITS_FINDING_RAW_<tplName>_PACKAGE_FIRST.)

The above proposed implementation would solve the Spack binary install use case by setting <Project>_SUPER_INSTALL_PREFIX to the base Spack package install dir and then all paths would be relative to that directory as well.

NOTE: We would have to also make all library paths relative as well according to the above process (i.e. based on the values of <ExternalPackage>_USE_RELATIVE_PATH and <Project>_SUPER_INSTALL_PREFIX).