Compile commands fallback logic can miss changes when using multiple configurations with different compile_commands.json paths

[yiftahw]

Environment

• OS and Version: Windows 10
• VS Code Version: 1.95.1
• C/C++ Extension Version: V1.22.11
• If using SSH remote, specify OS of remote machine:

Bug Summary and Steps to Reproduce

Bug Summary:
Assuming file watchers have failed/closed, the fallback logic CppProperties.checkCompileCommands can fail to detect changes in a compile_commands.json from a different configuration index (even when later switching to that configuration index)

Steps to reproduce:
Assume the following c_cpp_properties.json (only relevant parts shown)

{
    "configurations": [
        {
            "name": "compdb1",
            "compileCommands": "${workspaceFolder}/compile_commands_1.json",
        },
        {
            "name": "compdb2",
            "compileCommands": "${workspaceFolder}/compile_commands_2.json",
        }
    ],
    "version": 4
}

1. Assume we are using compdb1
2. Assume file watchers failed/closed on any of the example reasons:
   • We can force the file watchers to be closed by reproducing the steps described in Compile commands file watchers are leaked without being closed #12946.
   • fs.watch loses track of the file on Linux if file is deleted/doesn't exist. (on Linux, fs.watch tracks by inode)
   • Failed to create a file watcher by crossing the inotify limit on Linux.
3. Update compile_commands_2.json (by touching or actually compiling some CMake project)
   • Assuming file watchers are closed/failed, no event is triggered on this change.
   • checkCompileCommands() only checks the file used by the current configuration, no event is triggered on this change.
4. Update compile_commands_1.json
   • Now, compile_commands_1.json is newer than compile_commands_2.json.
   • CppProperties.compileCommandsFileWatcherFallbackTime is assigned compile_commands_1.json's timestamp.
5. Switch to compdb2
   • File watchers are re-created, but no event is triggered as compile_commands_2.json has changed before re-initializing the file watchers.
   • CppProperties.compileCommandsFileWatcherFallbackTime is a newer timestamp than compile_commands_2.json's timestamp, so checkCompileCommands() does not trigger an event.

Configuration and Logs

{
    "configurations": [
        {
            "name": "compdb1",
            "compileCommands": "${workspaceFolder}/compile_commands_1.json",
        },
        {
            "name": "compdb2",
            "compileCommands": "${workspaceFolder}/compile_commands_2.json",
        }
    ],
    "version": 4
}

Other Extensions

No response

Additional context

No response