This should be parsed as a dimension with a unit of `e` followed by a delim token `+`.
I didn't verify this with the specification, so maybe good to review relevant sections.
https://github.com/romainmenke/css-tokenizer-tests/blob/main/CHANGELOG.md#111
Yep this looks correct.
> If the [next 2 or 3 input code points](https://drafts.csswg.org/css-syntax/#next-input-code-point) are U+0045 LATIN CAPITAL LETTER E (E) or U+0065 LATIN SMALL LETTER E (e), optionally followed by U+002D HYPHEN-MINUS (-) or U+002B PLUS SIGN (+), followed by a [digit](https://drafts.csswg.org/css-syntax/#digit), then:
My reading is that it _must_ include both the plus sign and the digit to continue parsing the exponent.
@romainmenke also noticed https://github.com/romainmenke/css-tokenizer-tests/commit/3b31516cd9147f6d19d748dcc0cf80bf9ac145a8 so I've released https://github.com/keithamus/csslex/releases/tag/v1.0.4 to fix that ๐