Further restrict layer names

[samtay]

The editor currently allows a-zA-Z0-9,._+- when renaming layers. However using a hyphen e.g. SYM-1 fails to build for me with this error:

devicetree error: /tmp/zmk-config/config/corne.keymap:236 (column 11): parse error: expected '{', '=', or ';'

[nickcoutsos]

Hah, that's something!

Interestingly, layer names can be hyphenated, per the devicetree spec:

Valid characters for node names

Character	Description
0-9	digit
a-z	lowercase letter
A-Z	uppercase letter
,	comma
.	period
_	underscore
+	plus sign
-	dash

The node-name shall start with a lower or uppercase character and should describe the general class of device.

What's happening here is SYM-1 includes a pre-processor identifier. This gets evaluated before the devicetree compiler so you end up with a layer named 2-1 which isn't valid. I think in this case even SYM would be an invalid layer name for the same reason.

My advice would be to think about whether or not you'd prefer to use these identifiers. When parsing the keymap I do a small amount of evaluation but that's to deal with identifiers used in bindings (e.g. &mo SYM). This helps the app to handle the initial loading of the keymap, but when saving changes it won't attempt to map layer indices to potential layer identifiers.