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如何从可扩展函数内部发出错误信号？

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如何从可扩展函数内部发出错误信号？

我想在可扩展函数内进行一些错误检查。但我发出错误信号的尝试没有得到正确处理，而是返回到输入流——这与我的预期相反。

代码如下：

\documentclass{article}
\usepackage{pstricks,pst-eucl}
\psset{unit=0.25cm}
\usepackage{xparse}
\ExplSyntaxOn
\msg_new:nnnn {testing}{testing}{illegal~property}{}
%% property list
\prop_new:N \g__ace_all_properties_plist
%% setter
\cs_new_protected:Npn \__ace_set_property:nn #1#2
    {
        \prop_gput:Nnn \g__ace_all_properties_plist { #1 } { #2 }
    }
%% getter
\cs_new:Npn \__ace_get_property:n #1
    {
        \prop_get:Nn \g__ace_all_properties_plist { #1 }
    }
%%--- User interface for settr and gettr
\DeclareDocumentCommand{\settr}{ m m }
    {
        \__ace_set_property:nn { #1 }{ #2 }
    }
\DeclareExpandableDocumentCommand{\gettr}{ m }
    {
        \prop_if_in:NnTF \g__ace_all_properties_plist { #1 }
            {
                \__ace_get_property:n { #1 }
            }
            {
                %% this next line does not get executed
                %% even when there #1 is not in the list
                %<var 1>%\msg_info_text:n { #1 ~ is ~ not ~ defined }
                \msg_fatal_text:n { testing}
            }

    }        
\ExplSyntaxOff
\pagestyle{empty}
\begin{document}
\settr{displacement}{10}%

This picture gets processed correctly\par
\begin{pspicture}(0,0)(10,10)
    \pstGeonode[PointName=default,PointSymbol=default,PosAngle=0](0,0){A}(0,1){B}
    \pstTranslation[DistCoef=\gettr{displacement}]{A}{B}{A}[C]
\end{pspicture}

\vspace{1cm}

No error signaled here $\rightarrow$
\gettr{unknownproperty}

\vspace{1cm}

This picture should signal an error when commented line uncommented\par
\begin{pspicture}(0,0)(10,10)
    \pstGeonode[PointName=default,PointSymbol=default,PosAngle=0](0,0){A}(0,1){B}
    %\pstTranslation[DistCoef=\gettr{unknown-property}]{A}{B}{A}[C]
\end{pspicture}

\end{document}

\msg_term:x最初，我认为这是从可扩展函数中调用保护函数的问题。但是，即使使用 using ，我的错误也无法正确触发\mgs_fatal_text:n。后一种方法并不是我真正想要的。但以任何方式发出错误信号都会很好。

编辑

根据@DavidCarlisle 的建议，我尝试更换

\msg_fatal_text:n{ testing }

和

\ERROR

因此，编译停止了，但由于发出了错误类型的错误消息，我可以想象我会浪费很多时间来寻找错误的错误。因此，\ERROR我没有尝试

\use:c { Attempting ~ to ~ call ~ undefined ~ property -> {#1} }

我认为至少这样，我会得到一个错误，更清楚地表明真正的问题是什么。但这根本不是一个错误——与我的预期相反。

答案1

如果您实际上想要在仅扩展上下文（例如\write或 PS）中生成错误\special，通常的方法就是使用未定义的命令，例如\ERROR您无法从那里触发任何其他错误（并且 LaTeX3 无法真正改变这一点）。

! Undefined control sequence.
l.1 ...ptingToCallUndefinedPropertyunknownproperty



\documentclass{article}
\usepackage{pstricks,pst-eucl}
\psset{unit=0.25cm}
\usepackage{xparse}
\ExplSyntaxOn
\msg_new:nnnn {testing}{testing}{illegal~property}{}
%% property list
\prop_new:N \g__ace_all_properties_plist
%% setter
\cs_new_protected:Npn \__ace_set_property:nn #1#2
    {
        \prop_gput:Nnn \g__ace_all_properties_plist { #1 } { #2 }
    }
%% getter
\cs_new:Npn \__ace_get_property:n #1
    {
        \prop_get:Nn \g__ace_all_properties_plist { #1 }
    }
%%--- User interface for settr and gettr
\DeclareDocumentCommand{\settr}{ m m }
    {
        \__ace_set_property:nn { #1 }{ #2 }
    }
\DeclareExpandableDocumentCommand{\gettr}{ m }
    {
        \prop_if_in:NnTF \g__ace_all_properties_plist { #1 }
            {
                \__ace_get_property:n { #1 }
            }
            {
                %% this next line does not get executed
                %% even when there #1 is not in the list
                %<var 1>%\msg_info_text:n { #1 ~ is ~ not ~ defined }
\foo{ Attempting  To  Call  Undefined  Property  #1 }
            }

    }

\ExplSyntaxOff

{\catcode`\@=0
@catcode`\\=12
@gdef@foo#1{@scantokens{\#1}}}

\pagestyle{empty}
\begin{document}
\settr{displacement}{10}%

This picture gets processed correctly\par
\begin{pspicture}(0,0)(10,10)
    \pstGeonode[PointName=default,PointSymbol=default,PosAngle=0](0,0){A}(0,1){B}
    \pstTranslation[DistCoef=\gettr{displacement}]{A}{B}{A}[C]
\end{pspicture}

\vspace{1cm}

No error signaled here $\rightarrow$
\gettr{unknownproperty}

\vspace{1cm}

This picture should signal an error when commented line uncommented\par
\begin{pspicture}(0,0)(10,10)
    \pstGeonode[PointName=default,PointSymbol=default,PosAngle=0](0,0){A}(0,1){B}
    %\pstTranslation[DistCoef=\gettr{unknown-property}]{A}{B}{A}[C]
\end{pspicture}

\end{document}

（上午）大卫的把戏很有趣：

{
  \catcode`\|=0
  |catcode`\\=12
  |gdef|throwundefined#1{|scantokens{\#1}}
}
\throwundefined{x}

答案2

翻译@DavidCarlisle 的巧妙手法：

\cs_new:Npn \foo #1 
    {
        \tl_rescan:nn
            {  
                \char_set_catcode_escape:N \@
            }{
                @#1 
            }
    }

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