Overriding default`Shift-Alt-a` binding doesn't work

v6
1

Registering a keymap extension with Shift-Alt-a as key doesn’t seem to work when defaultKeymap is also used; the default command (toggleBlockComment) is run instead, even when the custom command is given higher precedence using Prec.

I think this is a bug, as I haven’t found any explanation in the documentation.
Other key bindings don’t seem to display this behavior (at least, toggleComment doesn’t); furthermore, using Alt-A instead of Shift-Alt-a does work.

Link to CodeMirror playground with very minimal reproduction:
https://codemirror.net/try/?c=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

2

You can use both Alt-A and Shift-Alt-a to describe this key, and the keymap logic will try the former first. Since the default keymap contains an Alt-A binding for toggleBlockComment, that will win out over your binding despite having a lower precedence, since it uses the canonical name. Changing your binding to also use Alt-A should help.

3

Ahh, that explains it. Perhaps this should be documented somewhere, if it isn’t already?