# GitHub Copilot Instructions: Strict Migration Task for `Lts/DDS`

Migrate only:

- `./qt-migration-legatus/qt5-before/qt5-legatus-legacy/Lts/DDS`
- to `./qt-migration-legatus/qt6-after/qt6-migrated-legatus/Lts/DDS`

## Execute
- Work autonomously.
- Do not stop after editing.
- Continue through analysis, fixes, Docker validation, and final reporting.
- Do not ask for confirmation unless the task is impossible, destructive, or source material is missing.

## Do Not Overreach
- Do not modify the legacy tree.
- Do not migrate sibling modules.
- Touch other files only if `Lts/DDS` cannot be configured, generated, compiled, linked, or validated without a minimal directly related fix.
- No cleanup, no opportunistic refactors, no unrelated modernization.

## Main Objective
Make `Lts/DDS` correctly integrated in the Qt6 build with deterministic RTI/codegen behavior.

## Mandatory Technical Checks
Verify and fix if needed:

- Qt5 -> Qt6 API compatibility in touched code
- C++17 compatibility in touched code
- local and parent `CMakeLists.txt`
- target inclusion
- include paths
- generated source/header registration
- RTI/codegen/KTextTemplate wiring
- generation-to-compilation dependency order
- build-tree output placement
- incremental rebuild triggers

## RTI / Codegen Rules
If `Lts/DDS` depends on generated files:

- reconstruct the legacy generation flow
- verify the Qt6 port preserves that flow
- ensure required generated `.h` / `.cpp` are produced automatically
- ensure they exist before consuming target compilation starts
- ensure generated `.cpp` are added to targets
- ensure generated headers are reachable through include paths
- ensure no stale source-tree or developer-local generated artifacts are required

Inspect and fix if needed:

- `add_custom_command(OUTPUT ...)`
- `BYPRODUCTS`
- `DEPENDS`
- `MAIN_DEPENDENCY`
- `WORKING_DIRECTORY`
- `COMMAND`
- `VERBATIM`
- `target_sources(...)`
- `add_dependencies(...)`
- `GENERATED`

Prefer build-tree outputs such as `${CMAKE_CURRENT_BINARY_DIR}` unless the repository clearly requires otherwise.

## No Stub / No Placeholder Rule for Missing Codegen Outputs
Do **not** create stub, dummy, placeholder, mock-generated, hand-written replacement, or minimally compilable substitute files for missing generated `.h` or `.cpp` outputs.

If required generated files are missing and cannot be produced by the real build-integrated generator flow, then:
- do not fabricate replacement files
- do not bypass the dependency by removing or weakening the integration
- do not claim build validation success
- report the exact missing files
- report the exact blocked generator step and root cause
- stop after applying only safe, reviewable fixes that do not simulate success

Any build that depends on invented stand-in files instead of real code-generated outputs must be reported as **not validated**.

## Hard Validation Rule for `BUILD_RTI=ON`
Do not declare `BUILD_RTI=ON` successful unless all of the following are proven:

- the build ran inside Docker
- old generated artifacts relevant to `Lts/DDS` were removed, invalidated, or proven irrelevant
- the generator actually ran during the Docker build if required
- new generated files were created in the current build
- consuming targets compiled against those newly generated files
- success did not depend on stale source-tree outputs, cached build outputs, or developer-local artifacts

If not proven, report `BUILD_RTI=ON` as **not fully validated**.

Before final validation, remove or invalidate any pre-existing generated artifacts relevant to `Lts/DDS` and prove regeneration happens from the build itself.

## Docker Authority
There are many Dockerfiles in the repo. For this task, only this one is authoritative:

- `./app/Dockerfile`

## Container Mount Rules
Use repository root mounted as:

- `/repo`

Required availability inside the container:

- repo root at `/repo`
- external dependencies at `/repo/external`
- RTI 7.7 at `/repo/external/rti_connext_dds-7.7.0`
- license file from `./rti_license.dat`, mapped read-only

If RTI requires environment variables or explicit license-path configuration, set them minimally and explicitly.

## Required Validation
Validate in Docker. If supported, validate both:

- `BUILD_RTI=ON`
- `BUILD_RTI=OFF`

For each relevant variant:
1. configure
2. build
3. verify generation
4. run tests if relevant
5. report result

Also verify:
- clean build from empty build directory
- incremental rebuild after changing a generator input/template/dependency
- non-RTI build does not require RTI/license if RTI is optional

## Start From
Use `/repo`-based paths. Adapt only if repository inspection proves it is required.

- `cmake -S /repo/qt-migration-legatus/qt6-after/qt6-migrated-legatus -B /repo/build -G Ninja -DCMAKE_BUILD_TYPE=Debug`
- `cmake --build /repo/build --parallel`
- `ctest --test-dir /repo/build --output-on-failure`

Add explicit `BUILD_RTI=ON` / `BUILD_RTI=OFF` configure flags if supported.

## If Tools Are Missing
- identify the exact missing dependency
- update only what is minimally required for the migration build
- rerun validation

## Final Response
Report only the essentials:

- validated or blocked
- whether RTI/codegen/KTextTemplate was involved
- whether generation timing was correct
- whether output placement was correct
- whether `BUILD_RTI=ON` succeeded
- whether `BUILD_RTI=OFF` succeeded
- whether `/repo/external/rti_connext_dds-7.7.0` worked
- whether `./rti_license.dat` mapping worked
- exact Docker commands used
- files changed
- each failure with:
  - command
  - key error
  - environment vs project
  - fix
- remaining blocker/risk