# Custom package error ! Missing = inserted for \ifnum

I am trying to create a very basic package for use with a font called HEJI2 (which provides some music symbols to use in-line). My code looks like this:

\ProvidesPackage{heji}[2019/12/9 v1.0]
\RequirePackage{fontspec}[2018/07/30 vv2.6h]

\newfontfamily{\HEfont}{HEJI2.ttf}

\makeatletter
\newcommand*{\fsize}{\dimexpr\f@size pt\relax}
\makeatother

\newcommand{\heji}[2]{\mbox{#1\hspace{0.3mm}\raisebox{0.25\fsize}{\large\HEfont #2}}}

\DeclareOption{accfirst}{
\renewcommand{\heji}[2]{\mbox{\raisebox{0.25\fsize}{\large\HEfont #2}#1}}
}

\ProcessOptions\relax

\endinput


Using the package seems to work, however when I compile it, I get the following (nonfatal) errors:

! Missing = insterted for \ifnum.
v
1.4

?
! Missing number, treated as zero.
v
1.4
?


Not sure what this means exactly. I appear to be able to return through the messages and I get a properly formatted .pdf in the end according to my package specifications. Would appreciate any help! (Compiling with Lualatex)

• Replace [2019/12/9 v1.0] by [2019/12/09 v1.0]... Dec 9 '19 at 1:31
• Thank you! Didn't even occur to me Dec 9 '19 at 1:35
• You're welcome! Some places (for instance texdoc usrguide) tell that this date should be in the format YYYY/MM/DD (which is now deprecated and should actually be in the ISO format YYYY-MM-DD), but it actually must be in this format. I wonder if this should be made a bit more flexible... Dec 9 '19 at 1:40

You can find, for example, in LaTeX2ε for authors (texdoc usrguide), section 3.2 Preamble commands:
That paragraph actually describes the second optional argument to \documentclass, but the date parser is the same. In The LaTeX2ε sources (texdoc source2e), section 68.2 Package name and version there is more or less the same paragraph about \ProvidesPackage.
Firstly, that date format is (still supported but) deprecated, and now the ISO format YYYY-MM-DD should be used instead.
And that requirement is not entirely true. Specifically the day field must be DD, while the other two can even be empty (common sense advises not to ;-), so for example \ProvidesPackage{heji}[1/1/09 v1.0] would've worked. You were unfortunate enough to remove the leading zero from the wrong place ;-)
• @ThomasNicholson Glad it helped :-) I'm not a font expert, so I may not be the best person to help you with this. Usually, if you are writing a font package, the font files will go in the fonts folder of your TeX distribution's directory tree, and TeX will look for them there. If it's not for a package (by package, I mean installed by your TeX distribution), then I think it gets trickier. I suggest you mark this question as solved and ask a new one, so that someone with more experience with fonts than me can help you :-) Dec 11 '19 at 20:33