amssymb require in sphinx.sty may break use of math font packages

[jfbu]

This is similar to #2290 which was fixed in 532e99c (stable)

Commit 19a7dfd added \RequirePackage{amssymb} to sphinx.sty. This commit is in master branch but not in 1.3.5 (hence I did not realize impact on a project of mine until trying it on master branch).

The problem is if one uses 'fontpkg' key to latex_elements to load some font packages. Among them, there may be math font packages, and the later loading of amssymb by sphinx.sty can cause conflicts. For example, using (in a lualatex project) \setmathfont{xits-math}, I got

(/usr/local/texlive/2015/texmf-dist/tex/latex/amsfonts/amssymb.sty
Package: amssymb 2013/01/14 v3.01 AMS font symbols


/usr/local/texlive/2015/texmf-dist/tex/latex/amsfonts/amssymb.sty:240: LaTeX Er
ror: Command `\eth' already defined.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.240 ...mbol{\eth}            {\mathord}{AMSb}{"67}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.


/usr/local/texlive/2015/texmf-dist/tex/latex/amsfonts/amssymb.sty:259: LaTeX Er
ror: Command `\digamma' already defined.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.259 ...mbol{\digamma}        {\mathord}{AMSb}{"7A}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.


/usr/local/texlive/2015/texmf-dist/tex/latex/amsfonts/amssymb.sty:265: LaTeX Er
ror: Command `\backepsilon' already defined.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.265 ...mbol{\backepsilon}    {\mathrel}{AMSb}{"7F}

Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.

The fix should be like for #2290 to move loading of amssymb earlier.

Actually amssymb loads automatically amsfonts. Hence one can reuse the 'amsfonts' key which was introduced in 532e99c and set its default value to r'\usepackage{amssymb}'.

(perhaps the key should be renamed to 'amssymb').

[tk0miya]

MEMO: the amssymb package came from #1971

[tk0miya]

In my environment, it must load the amsmath package earlier too.

So I would move both amsmath and amssymb to the position of amsfonts key.
And then, rename it to amsmath and assigns \usepackage{amsmath,amssymb} by default.
Of course, I will remove amsfonts installation hack from sphinx.ext.math*. It is already replaced by amssymb.

@xuhdev What do you think?

[xuhdev]

It looks good to me :)

[tk0miya]

Ok, I will modify it later.

[tk0miya]

Modified.
Thank you always :-)