Can I list the targets exported from a CMake config file, outside of a CMakeLists.txt which uses them?

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Summary

Issue: Attempting to list exported targets from a CMake config file outside of a CMakeLists.txt file using a simpler CMake command line.
Outcome: Not directly possible without invoking CMake in a project context.

Root Cause

  • CMake config files (e.g., FooConfig.cmake) are designed to be included in a CMakeLists.txt file.
  • They rely on CMake’s internal state and context to function, which is not available in isolation.

Why This Happens in Real Systems

  • CMake’s design: Config files are meant to be part of a build system, not standalone scripts.
  • Context dependency: Targets and variables are resolved within a CMake project’s scope.

Real-World Impact

  • Development inefficiency: Engineers cannot quickly inspect exported targets without setting up a project.
  • Debugging challenges: Troubleshooting config files requires additional setup.

Example or Code (if necessary and relevant)

# Example CMakeLists.txt to list targets
cmake_minimum_required(VERSION 3.10)
project(ListTargets)

find_package(Foo REQUIRED)

get_property(targets DIRECTORY PROPERTY IMPORTED_TARGETS)
message("Exported targets: ${targets}")

How Senior Engineers Fix It

  • Create a minimal project: Set up a CMakeLists.txt to include the config file and list targets.
  • Use CMake scripts: Write a custom CMake script to simulate a project environment.
  • Leverage cmake -P: Execute a CMake script directly with cmake -P to inspect variables.

Why Juniors Miss It

  • Lack of CMake internals knowledge: Juniors may not understand CMake’s context-dependent nature.
  • Overlooking documentation: CMake’s official documentation emphasizes project-based usage.
  • Assumption of standalone execution: Juniors may assume config files can be queried directly like scripts.

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