qt6-migration-pipeline/.github/prompts/combined-migration-compact.prompt.md

GitHub Copilot Instructions: Qt5/C++11 to Qt6/C++17 Migration

Mission

Migrate the legacy Qt5/C++11 desktop application to Qt6/C++17, preserve behavior unless change is strictly required, and validate the result completely in the repository’s Docker-based CI workflow.

Operating Mode

• Work autonomously from analysis through validation.
• Do not stop after editing code.
• Continue until configure, build, tests, and policy checks have been attempted in Docker.
• Do not ask for confirmation during normal implementation.
• Stop early only if required source material is missing, the task is impossible, or a destructive action would be required.

Boundaries

• Read the legacy project from ./qt-migration-legatus/qt5-before/qt5-legatus-legacy.
• Write the migrated project to ./qt-migration-legatus/qt6-after/qt6-migrated-legatus.
• Do not modify the legacy source tree in place.
• Limit changes to the target tree and only the CI/build/test files needed to support migration and validation.

Main Migration Targets

• Upgrade Qt5 to Qt6.
• Upgrade C++11/14/17 code to C++17.
• Keep Qt Core, Gui, and Widgets explicitly linked.
• Replace QRegExp with QRegularExpression.
• Replace QDesktopWidget and QApplication::desktop() with QScreen-based Qt6 APIs.
• Remove legacy QTextCodec usage and adopt Qt6-safe text handling.
• Replace old SIGNAL/SLOT syntax with function-pointer connect syntax.
• Replace 0/NULL pointer literals with nullptr.
• Preserve .ui and .qrc integration.
• Preserve behavior unless Qt6 compatibility requires adaptation.

C++17 Modernization Rules

• Preserve semantics first; modernize second.
• Use auto when the type is obvious; avoid it when it hides important type information.
• Prefer structured bindings where clearer.
• Replace raw owning pointers/manual delete with RAII, usually std::unique_ptr.
• Use std::make_unique / std::make_shared; use std::shared_ptr only for real shared ownership.
• Use std::string_view only when lifetime safety is clear.
• Prefer std::span for non-owning contiguous data; use std::mdspan only when multidimensional access clearly benefits.
• Prefer .contains() over find(...) != end() where available.
• Prefer algorithms and ranges over manual loops when readability improves.
• Use [[nodiscard]] when ignoring a result is likely a bug.
• Prefer early returns over deeply nested control flow.
• Use std::optional monadic operations (and_then, transform, or_else) when clearer.
• Prefer constexpr, if constexpr, concepts, and requires over legacy std::enable_if/SFINAE where practical.
• Add noexcept, override, final, = default, and = delete where correct and useful.
• Prefer enum class over unscoped enums where practical.
• Prefer std::print / std::println when supported by the toolchain.
• Prefer typed std::chrono durations and std::jthread where appropriate.

Safety Rules

• Do not change business logic unless explicitly requested or required for Qt6 compatibility.
• Do not introduce unsupported Qt6/C++17 features.
• Do not silently change ABI, ownership, lifetime, exception behavior, performance, UI behavior, or event ordering.
• Do not worsen readability for the sake of modernization.
• Do not refactor code.
• Avoid dangling references, dangling std::string_view, and ownership ambiguity.
• Keep includes minimal and preserve repository-local formatting/style.
• no code cleanup
• no renaming
• no extraction of functions/classes
• no restructuring of logic
• no stylistic rewrites
• no dependency modernization
• no opportunistic improvements
• no behavior changes beyond path/build necessity

Tests

• For every code change inside a method, add at least three tests covering the changed behavior.
• Place generated tests in ./qt-migration-legatus/qt6-after/qt6-migrated-legatus/tests.
• Use policy-compatible test filenames such as:
  • test_<name>.cpp
  • <name>_test.cpp
  • <name>test.cpp
  • <name>gtest.cpp as searched for in ./qt-migration-legatus/ci/check_pr_policies.py
• Update CMake so the migrated app and all tests build and run with CTest.
• Ensure all tests are registered with CTest.

Docker-First Validation

Use lifemaps/ci-cpp:latest as the authoritative environment. Do not substitute host tools for missing container tools. Treat ./qt-migration-legatus/ci/Dockerfile.ci as the source of truth for CI dependencies.

Required validation sequence

1. Configure in Docker
2. Build in Docker
3. Run tests in Docker
4. If tests pass, run python3 ci/check_pr_policies.py in Docker

Recommended commands

• Configure: cmake -S ./qt-migration-legatus/qt6-after/qt6-migrated-legatus -B build -G Ninja -DCMAKE_BUILD_TYPE=Debug
• Build: cmake --build build --parallel
• Test: ctest --test-dir build --output-on-failure
• Policy: python3 ./qt-migration-legatus/ci/check_pr_policies.py

Adapt paths/flags only if repository inspection proves they must differ.

Missing-Tool Remediation

If Docker validation fails because a required tool/package is missing:

• identify the exact missing dependency
• update ./qt-migration-legatus/ci/Dockerfile.ci minimally
• rebuild lifemaps/ci-cpp:latest
• rerun the full validation sequence

Continue until:

• validation succeeds, or
• the next blocker is a genuine project/code issue

Failure Classification

Environment failures:

• command not found
• missing compiler/toolchain utility
• missing Qt dev package
• missing CMake/Ninja/CTest support tool
• missing dependency required by ./qt-migration-legatus/ci/check_pr_policies.py

Project failures:

• compile errors
• linker errors
• failing tests
• formatting/policy failures caused by migration changes

Policy Awareness

• ./qt-migration-legatus/ci/check_pr_policies.py checks formatting for changed C/C++ files, expects related tests, and verifies commit-signature conditions in its diff range.
• Ensure Docker validation runs with mounted workspace and git metadata available.
• Do not claim success unless the policy script passes.

Execution Plan

1. Inspect ./qt-migration-legatus/ and the target tree.
2. Identify Qt5 and legacy C++ constructs to migrate.
3. Migrate incrementally in qt6-after/qt6-migrated-legatus.
4. Add/update tests with each behavior-relevant change.
5. Update CMake/test registration.
6. Validate in Docker.
7. If missing dependencies are found, update ./qt-migration-legatus/ci/Dockerfile.ci, rebuild, and rerun.
8. Repeat until success or a real project defect remains.

Reporting

Group change explanations by:

• CMake / build-system migration
• Qt API replacements
• C++ modernization
• UI/resource preservation
• tests added
• ./qt-migration-legatus/ci/Dockerfile.ci / container updates

Also provide a concise changed-files summary.

Completion Criteria

Success requires:

• migrated project exists under ./qt-migration-legatus/qt6-after/qt6-migrated-legatus
• configure succeeds in Docker
• build succeeds in Docker
• tests succeed in Docker
• python3 ci/check_pr_policies.py succeeds in Docker after tests pass

Final Response

• State whether migration is fully validated or which blocker remains.
• List the exact Docker commands used for image rebuild, configure, build, test, and policy check.
• For every failed attempt, include:
  • exact command
  • key error
  • environment vs project classification
  • fix applied
• End with a short summary of any remaining blocker.