Enhance generator mismatch detection and clean-up logic

[hanniavalera]

This pull request addresses a regression affecting Visual Studio kits with Ninja-based build caches, enhances generator selection and fallback logic for Visual Studio kits, and introduces improved detection and handling of generator mismatches to prevent build failures. It also updates documentation to clarify generator selection behavior and adds targeted unit tests for generator mismatch detection.

Bug fixes and generator selection improvements:

• Fixed a regression where Visual Studio kits with an existing Ninja-based build cache would fail after updating CMake Tools due to a generator mismatch. Ninja is now again preferred when available, and for stale VS kits missing preferredGenerator, the correct VS generator is derived at runtime as a fallback. The extension now auto-cleans the build directory when a generator mismatch with CMakeCache.txt is detected, including during driver reloads triggered by generator-related setting changes. [1] [2] [3] [4]

• Improved generator selection logic for Visual Studio kits:

  • Kits scanned for known VS versions now get a preferredGenerator at scan time.
  • If a kit was scanned before support for a VS version, the correct generator is derived at runtime and only used after Ninja/Unix Makefiles fallbacks.
  • Documentation and code comments clarify the generator precedence order and fallback behavior. [1] [2] [3] [4] [5] [6] [7]

Testing and reliability:

• Added a pure helper function generatorMismatch to detect generator mismatches between the desired generator and the one cached in CMakeCache.txt, and exported it for direct unit testing. [1] [2]
• Added comprehensive unit tests for generator mismatch detection, covering a variety of scenarios including cache parsing and different generator combinations.

Documentation updates:

• Updated docs/kits.md to clarify how Visual Studio kits handle generator selection, when and how preferredGenerator is set or derived, and the order in which generators are considered. Also documented the new safety net for cleaning the build directory on generator mismatches. [1] [2] [3]

[Copilot]

Pull request overview

This PR improves generator selection and generator-mismatch handling in kits mode, primarily to prevent failures when a project’s existing CMakeCache.txt was produced with a different generator than the one newly selected (notably affecting Visual Studio kits and Ninja caches).

Changes:

• Add generator-mismatch detection in the driver and trigger clean-up when switching kits in-place.
• Refine Visual Studio kit generator preference handling (use preferredGenerator when present; derive VS generator only as a last-resort fallback).
• Update kits documentation + changelog entry; add unit tests for kit-change clean detection and cache generator parsing.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/drivers/cmakeDriver.ts	Adds _hasGeneratorChanged() and uses it during setKit() to decide whether to clean prior configuration.
src/kits/kit.ts	Minor refactor/clarification in VS generator derivation helpers.
test/unit-tests/kit-scan.test.ts	Adds regression tests for kitChangeNeedsClean() around preferredGenerator changes.
test/unit-tests/generator-mismatch.test.ts	Adds tests around reading CMAKE_GENERATOR from cache content.
docs/kits.md	Documents generator selection precedence and generator-mismatch clean behavior.
CHANGELOG.md	Adds a 1.23.51 bug-fix entry describing the regression fix.