`package:watcher` wrong events following case-ambiguous rename/delete on Windows and Mac

[davidmorgan]

If you rename foo -> Foo it current emits modify for foo and add for Foo, it should emit remove for foo and add for Foo.

You can see the confusion in VSCode on Windows if you do renames on the command line

echo "error" > error.dart
mv error.dart Error.dart
mv error.dart other.dart
mv other.dart error.dart

After commands 1..3 you should see (in "focus on problems view") the analyzer reporting that there is an error in the source file, but after the last command it reports nothing: the analyzer thinks the file has disappeared.

That's because the watcher never picked up that error.dart was gone, so it did not emit an add for it on the last rename; the analyzer on the other hand did notice that error.dart was gone, so in the end it concludes there is no file there.

This is low priority for watcher use in the IDE, since people mostly don't mess with the case of files. Still, if the fix is not too complex/expensive it'd be nice to do it right, or if it's too hard at least document it.

[davidmorgan]

Also an issue on Mac, and there is an additional issue on Mac: "delete" events arrive with the case of the delete operation, not the case of the file. If the case differs from what watcher is expecting, it doesn't match a known file and the delete is ignored.

Much simpler repro with VSCode on Mac for the "delete" problem: just delete a file on the command line using the wrong case, the delete works but the analyzer doesn't notice the file is gone.

echo "error" > error.dart
rm Error.dart

[lrhn]

Feels like an inherent consequence of trying to have an internal model of the file system, when that model doesn't match the actual behavior of the file system.

It's hard to match a file system's behavior when you need to know for each directory whether it's case sensitive, and if it isn't, which case folding it uses. (That can differ along a path that uses symbolic links to span multiple NTFS volumens).

If the OS/file system does not give you a way to canonicalize a path, it's probably impossible.