Expandafter issue

Question

The problem is as follows: I need to pass the same set of options (say angle=90, scale=0.85) to a given command (say includepdf) repeatedly. One approach is to save that option in some macro, say __Foo. The problem is includepdf[__Foo] causes an error. I have proposed two ways to solve it, one with expandafter, another with a custom function to be invoked with the command and the option. Neither of which satisfy me. Is there there a tool (in etoolbox?) to create a new function from includepdf, say includepdfbis, such that I can use it like this: includepdfbis[__Foo]?
documentclass{article}
usepackage{mwe}
usepackage{pdfpages}
usepackage{xparse}

ExplSyntaxOn
def__Foo{angle=90, scale=0.85}

cs_new_protected:Nn__erw_pass_option:Nn{#1[#2]}
cs_generate_variant:Nn __erw_pass_option:Nn {Ne}

ExplSyntaxOff

begin{document}

ExplSyntaxOn

%includepdf[__Foo]{example-image-a} % ERROR: Package keyval Error: angle=90,scale=0.85 undefined.

expandafterincludepdfexpandafter[__Foo]{example-image-a}

__erw_pass_option:Ne includepdf{__Foo}{example-image-a}

ExplSyntaxOff

end{document}

David Carlisle · Accepted Answer

As it is harmless to apply expandafter to the filename if no option is used, you can just unconditionally use the form you showed but wrapped in a macro.
documentclass{article}

usepackage{pdfpages}

% you would need expl3 package in older latex releases.
ExplSyntaxOn
def__Foo{angle=90, scale=0.85}
% def not really the expl3 way but as you started..
defincludepdfbis{expandafterincludepdfexpandafter}
ExplSyntaxOff

begin{document}

ExplSyntaxOn

includepdfbis[__Foo]{example-image-a}

ExplSyntaxOff

end{document}

egreg · Answer

You're better to define your own key.
documentclass{article}
usepackage{pdfpages}

makeatletter
define@key{Gin}{Foo}[]{setkeys{Gin}{angle=90, scale=0.85}}
makeatother

begin{document}

includepdf[Foo]{example-image-a}

end{document}

Expandafter issue

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