Limits of CLion’s Automatic CMake Project Reload During Migration

CLion does not have a specific configuration setting to enable automatic detection of external CMakeLists.txt changes independently of its general file system synchronization. The "Reload project on CMakeLists.txt changes" setting primarily triggers when edits occur within the IDE's own editor.

External Change Detection and the Sync Now Button

The Sync Now button appears in the CMake tool window when CLion detects a mismatch between the current CMake cache and the source files. This typically happens when the IDE regains focus after an external process has modified the project files, or when the internal file system watcher flags a change.

How to Force Synchronization

Because the Sync Now button is context-dependent and cannot be permanently forced to be visible, use these methods to ensure your project is up to date:

• Manual Reload: Press Ctrl+Shift+A (Find Action) and type Reload CMake Project.
• Tool Window Refresh: Open the CMake tool window and click the Reload (circular arrow) icon.
• System Sync: Ensure Settings > Appearance & Behavior > System Settings > Synchronize files on frame activation is checked. This forces CLion to check for external changes whenever you switch back to the IDE window.

Zero-Downtime Migration and Plugins

There are currently no third-party plugins that provide a "zero-downtime" migration by bypassing the native CMake reload mechanism. Most CMake-related plugins in the JetBrains Marketplace provide syntax helpers or management UI but still rely on the IDE's core reload actions to update the build configuration.

Practical Verification

To verify if your IDE is detecting external changes correctly, follow these steps:

1. Open CMakeLists.txt in an external editor (e.g., Notepad or Vim).
2. Add a dummy comment or a new source file to the list and save the file.
3. Return to CLion. If the Sync Now notification does not appear, check the CMake tool window for the reload icon.
4. If the build still uses stale data, use Build > Clean or manually delete the cmake-build-debug (or equivalent) folder to force a clean cache generation.

Note: If you are using a network drive or a virtualized file system (like WSL or Docker volumes), the file system watcher may fail to trigger. In these environments, manual reloads are mandatory.