Only set FPRIME_PROJECT_ROOT when fprime is the top-level project

[devin-ai-integration]

Related Issue(s)	N/A
Has Unit Tests (y/n)	n
Documentation Included (y/n)	n
Generative AI was used in this contribution (y/n)	y

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Change Description

Guard the FPRIME_PROJECT_ROOT cache variable in CMakeLists.txt so it is only set when F Prime is the top-level CMake project (CMAKE_SOURCE_DIR == CMAKE_CURRENT_SOURCE_DIR). When F Prime is included via add_subdirectory(), the parent project is expected to set FPRIME_PROJECT_ROOT to its own root directory.

Rationale

When using F Prime as a CMake subdirectory via add_subdirectory(), the unconditional set(FPRIME_PROJECT_ROOT ... FORCE) overwrites the parent project's root with fprime's own directory. This causes get_nearest_build_root to fail for project-level modules since they are not under lib/fprime/.

This fix enables the add_subdirectory pattern used in the fprime_add_subdirectory_reference project.

Testing/Review Recommendations

• Verified that the fprime_add_subdirectory_reference project generates and builds successfully (471 targets) with this fix applied.
• When fprime is the top-level project (standalone build), behavior is unchanged since the guard evaluates to true.

Future Work

Additional fixes may be needed in F Prime's cmake system to fully support the add_subdirectory() pattern (e.g., CMAKE_MODULE_PATH propagation, include directory scoping).

AI Usage (see policy)

AI (Devin) was used to identify the root cause and implement the fix while building the fprime_add_subdirectory_reference project.

Link to Devin session: https://nasa-jpl-demo.devinenterprise.com/sessions/0f7a8879993340a3a8351d9b087177c0

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[devin-ai-integration]

Original prompt from michael.d.starch

will you create a new fprime reference. This one should add fprime as a make subdirectory (add_subdirectory). Use the branch cmake-test-fixes on the lestarch fork. Make sure the reference uses the new format with a project folder containing a deployment folder.

Use fprime-bootstrap to build the project and then fprime-until new to make development after sourcing the venv and cding into the project folder. Then make a commit as a baseline.

Generate and build and then come talk to me….fix errors with the deployment and project…but come back to me if you need a change in fprime.

[devin-ai-integration]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.