error handling if language is changed

[u-fischer]

If I compile a simple document say using english as language:

\documentclass{article}
\usepackage{polyglossia}
\setmainlanguage{english}
\begin{document}
blub
\end{document}

and then switch from english to e.g. brazil the remaining \selectlanguage in the aux-file triggers tons of error and then hangs. See below.

Could this please be improved? I know that I can delete all auxiliary files first, but it slows down testing and debugging a lot if you have to do that all the time. A similar test with babel gives no error at all but only a warning about the unknown language.

! Critical Package polyglossia Error: The language english is not loaded. You
(polyglossia)                         should load it.

Type <return> to continue.
 ...                                              

l.2 \selectlanguage *{english}

? 

! Package polyglossia Error: Unknown direction .

See the polyglossia package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 
! Undefined control sequence.
<argument> \setnonlatin 

l.2 \selectlanguage *{english}

? 

! Package etoolbox Error: \rmfamily undefined.

See the etoolbox package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 

! Package etoolbox Error: \sffamily undefined.

See the etoolbox package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 

! Package etoolbox Error: \ttfamily undefined.

See the etoolbox package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 

Package polyglossia Warning: \@font@rm  is not defined on input line 2.

Package polyglossia Warning: \@language  is not defined on input line 2.

! Package polyglossia Error: language  is not loaded. Please load it before usi
ng it..

See the polyglossia package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 

! Package polyglossia Error: Could not retrieve key frenchspacing for language 
"".

See the polyglossia package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 
The property list \polyglossia@langsetup contains the pairs (without outer
braces):
>  {latex/script}  =>  {latin}
>  {latex/lcscript}  =>  {latin}
>  {latex/scripttag}  =>  {}
>  {latex/language}  =>  {Latex}
>  {latex/langtag}  =>  {ENG}
>  {latex/bcp47}  =>  {}
>  {latex/hyphennames}  =>  {english}
>  {latex/direction}  =>  {LR}
>  {latex/hyphenmins}  =>  {2,3}
>  {latex/frenchspacing}  =>  {false}
>  {latex/indentfirst}  =>  {false}
>  {latex/fontsetup}  =>  {true}
>  {latex/envname}  =>  {latex}
>  {latex/babelname}  =>  {latex}
>  {latex/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/DefineCommandsCmd}  =>  {use_none:n}
>  {portuguese/script}  =>  {latin}
>  {portuguese/lcscript}  =>  {latin}
>  {portuguese/scripttag}  =>  {}
>  {portuguese/language}  =>  {Portuguese}
>  {portuguese/langtag}  =>  {PTG}
>  {portuguese/bcp47}  =>  {pt-BR}
>  {portuguese/hyphennames}  =>  {portuges,portuguese}
>  {portuguese/direction}  =>  {LR}
>  {portuguese/hyphenmins}  =>  {2,3}
>  {portuguese/frenchspacing}  =>  {false}
>  {portuguese/indentfirst}  =>  {false}
>  {portuguese/fontsetup}  =>  {true}
>  {portuguese/envname}  =>  {portuguese}
>  {portuguese/babelname}  =>  {brazil}
>  {portuguese/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/DefineCommandsCmd}  =>  {xpg_define_language_commands:e}.
<recently read> }

l.2 \selectlanguage *{english}

? 

! Package polyglossia Error: Could not retrieve key direction for language "".

See the polyglossia package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 
The property list \polyglossia@langsetup contains the pairs (without outer
braces):
>  {latex/script}  =>  {latin}
>  {latex/lcscript}  =>  {latin}
>  {latex/scripttag}  =>  {}
>  {latex/language}  =>  {Latex}
>  {latex/langtag}  =>  {ENG}
>  {latex/bcp47}  =>  {}
>  {latex/hyphennames}  =>  {english}
>  {latex/direction}  =>  {LR}
>  {latex/hyphenmins}  =>  {2,3}
>  {latex/frenchspacing}  =>  {false}
>  {latex/indentfirst}  =>  {false}
>  {latex/fontsetup}  =>  {true}
>  {latex/envname}  =>  {latex}
>  {latex/babelname}  =>  {latex}
>  {latex/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/DefineCommandsCmd}  =>  {use_none:n}
>  {portuguese/script}  =>  {latin}
>  {portuguese/lcscript}  =>  {latin}
>  {portuguese/scripttag}  =>  {}
>  {portuguese/language}  =>  {Portuguese}
>  {portuguese/langtag}  =>  {PTG}
>  {portuguese/bcp47}  =>  {pt-BR}
>  {portuguese/hyphennames}  =>  {portuges,portuguese}
>  {portuguese/direction}  =>  {LR}
>  {portuguese/hyphenmins}  =>  {2,3}
>  {portuguese/frenchspacing}  =>  {false}
>  {portuguese/indentfirst}  =>  {false}
>  {portuguese/fontsetup}  =>  {true}
>  {portuguese/envname}  =>  {portuguese}
>  {portuguese/babelname}  =>  {brazil}
>  {portuguese/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/DefineCommandsCmd}  =>  {xpg_define_language_commands:e}.
<recently read> }

l.2 \selectlanguage *{english}

? 

! LaTeX Error: Missing \begin{document}.

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

l.2 \selectlanguage *{english}

? 

! Package polyglossia Error: Could not retrieve key indentfirst for language ""
.

See the polyglossia package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.2 \selectlanguage *{english}

? 
The property list \polyglossia@langsetup contains the pairs (without outer
braces):
>  {latex/script}  =>  {latin}
>  {latex/lcscript}  =>  {latin}
>  {latex/scripttag}  =>  {}
>  {latex/language}  =>  {Latex}
>  {latex/langtag}  =>  {ENG}
>  {latex/bcp47}  =>  {}
>  {latex/hyphennames}  =>  {english}
>  {latex/direction}  =>  {LR}
>  {latex/hyphenmins}  =>  {2,3}
>  {latex/frenchspacing}  =>  {false}
>  {latex/indentfirst}  =>  {false}
>  {latex/fontsetup}  =>  {true}
>  {latex/envname}  =>  {latex}
>  {latex/babelname}  =>  {latex}
>  {latex/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {latex/DefineCommandsCmd}  =>  {use_none:n}
>  {portuguese/script}  =>  {latin}
>  {portuguese/lcscript}  =>  {latin}
>  {portuguese/scripttag}  =>  {}
>  {portuguese/language}  =>  {Portuguese}
>  {portuguese/langtag}  =>  {PTG}
>  {portuguese/bcp47}  =>  {pt-BR}
>  {portuguese/hyphennames}  =>  {portuges,portuguese}
>  {portuguese/direction}  =>  {LR}
>  {portuguese/hyphenmins}  =>  {2,3}
>  {portuguese/frenchspacing}  =>  {false}
>  {portuguese/indentfirst}  =>  {false}
>  {portuguese/fontsetup}  =>  {true}
>  {portuguese/envname}  =>  {portuguese}
>  {portuguese/babelname}  =>  {brazil}
>  {portuguese/localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/Localnumeral}  =>  {polyglossia@C@localnumeral}
>  {portuguese/DefineCommandsCmd}  =>  {xpg_define_language_commands:e}.
<recently read> }

l.2 \selectlanguage *{english}

? 

[jspitz]

Fixed. We now use a special \xselectlanguage command in the aux file that does only warn, not error.

[u-fischer]

well that resolves the problem in the aux. But if one uses an unknown language in the document polyglossia gets also into the error frenzy and then hangs:

\documentclass{article}
\usepackage{polyglossia}
\setmainlanguage{german}
\begin{document}
aaa

\selectlanguage{french}

bbb
\end{document}

I don't understand it. It does detect that the language is not declared. Then why does it nevertheless try to set it up? It should be trivial to change \__xpg_msg_if_lang_not_loaded:n to a proper test that aborts in this case.

[jspitz]

Sure, but that's not the issue you reported. I'll have a look.

[jspitz]

We bail out early now.