\@ifpackageloaded not working as expected - TeX

samcarter replying to Skillmon

<3

samcarter replying to Skillmon

While under the hood, it might be the same, I think it would be interesting to see hooks in action

Skillmon replying to samcarter

Wouldn't that just be your answer with one token exchanged for some other? More importantly, with up-to-date LaTeX2e, `etoolbox` will use the hooks internally, so this will be exactly the same behaviour wise (except for one step of expansion).

samcarter

@Skillmon It would be really nice to see your hook comments as an answer!

निरंजन replying to Skillmon

Oh, okay. I'll change things accordingly now. Thanks for the help.

Skillmon replying to निरंजन

You mean why not include typeset material in `\AtBeginDocument`/`\AddToHook{begindocument}`? Because LaTeX could still be initializing stuff, basically you're still somewhat inside the preamble.

निरंजन replying to Skillmon

Why not to execute it with `\begin{document}` itself?

Skillmon replying to निरंजन

The important bit is: It is not safe to include typeset material inside of `\AtBeginDocument`, stuff which should end up in the output should always go inside of `\AddToHook{begindocument/end}`.

निरंजन replying to Skillmon

Okay. Thanks for the references.

Skillmon replying to निरंजन

Take a look at `texdoc lthooks`, `texdoc ltshipout`, and `texdoc ltfilehook` (I hope I didn't forget anything)

निरंजन replying to samcarter

Never knew about so many tricks one can do with the code.

निरंजन replying to Skillmon

Ah, I missed it. Sorry

निरंजन replying to Skillmon

What are other hooks instead of `env`?

Skillmon replying to निरंजन

not quite perfect. It's more like the following:  
  
```  
% code provided in \AtEndPreamble (or \AddToHook{begindocument/before})  
\begin{document} % also executes code provided in \AtBeginDocument (or \AddTohook{begindocument}  
% code provided in \AddToHook{begindocument/end}

निरंजन replying to Skillmon

That's so cool! :)

Skillmon replying to निरंजन

yes, those would be `\AddToHook{env/xxx/end}{<stuff>}` (inside the environment) and `\AddToHook{env/xxx/after}{<stuff>}` (outside the environment).

Skillmon replying to samcarter

From the documentation `lthooks-doc.pdf`:  
  
> The generic hooks executed by `\begin` also exist, i.e., `env/document/before` and
`env/document/begin`, but with this special environment it is better use the dedicated one-time hooks above.

निरंजन replying to Skillmon

Okay. Is there anything like `\AddToHook{env/xxx/end}{<stuff>}` for adding something after the end of an environment?

samcarter replying to निरंजन

yes, that's basically the difference, AtEndPreamble gets executed before AtBeginDocument

samcarter replying to Skillmon

I have no idea, Joseph added them

निरंजन replying to samcarter

But how do they differ? I mean why is `\AtBeginDocument` different from `\AtEndPreamble`? Is it the following?

```
%% Code provided in \AtEndPreamble
\begin{document}
%% Code provided in \AtBeginDocument?
```

Skillmon replying to निरंजन

Yes, that would be `\AddToHook{env/xxx/begin}{<stuff>}` (inside the environment) or `\AddToHook{env/xxx/before}{<stuff>}` (outside the environment).

samcarter replying to निरंजन

yes, or from etoolbox `\AtBeginEnvironment{⟨environment⟩}{⟨code⟩}`

निरंजन replying to Skillmon

Does hook mean any `begin{xxx}`? For example if I want to execute a certain code before the start of every instance of environment xxx, would this mechanism be useful to me?

Skillmon replying to samcarter

oh, should've read the chat :) But note that `\AddToHook{begindocument/before}` is documented to be equivalent to `\AtEndPreamble`, unlike `\AddToHook{env/document/begin}` .

samcarter replying to निरंजन

It depends what you would like to achieve. If you do this at end preamble, a user/other package can overwrite this with `\AtBeginDocument`.

samcarter replying to Skillmon

I'll leave this to somebody more familiar with hook :)

samcarter replying to Skillmon

::: quote 1875 103604 a0362e7b92f294b0635b00a01513de326955d3c184409f901b5c2ac1637ec99c 255,239,236 159,57,61
samcarter[ *— an hour ago*](#c103604)  
>You could also be all modern and use this new hook thingy like in https://github.com/josephwright/beamer/blob/bdc36d143eedafc33615fcd6d0a0beb7f1223253/base/beamerbasecompatibility.sty#L58-L60 Maybe someone more familiar with this can write up an answer about this.
:::

Skillmon

@samcarter, re: [your answer](#a2060), with up to date LaTeX kernels you don't have to load `etoolbox`, you can use `\AddToHook{begindocument/before}{<code>}` instead of `\AtEndPreamble`.

निरंजन

@samcarter, re: [your answer](#a2060), It works now. Thanks. Unrelated to the question, but do you think changing [this](https://gitlab.com/niruvt/marathi/-/blob/master/marathi/marathi.dtx#L392-403) part of the code with `\AtEndPreamble` instead of `\AtBeginDocument` would be safe? I would love to use a mechanism uniformly. What's the exact difference between these two?

निरंजन replying to samcarter

I'll edit mine. Done now.

निरंजन replying to samcarter

Okay, thanks for letting me know about it.

निरंजन replying to samcarter

Okay.

samcarter

P.S. A minimal working example to demonstrate the problem:  
```  
\documentclass{article}

\makeatletter
\AtBeginDocument{%
  \@ifpackageloaded{csquotes}{}{%
    \RequirePackage[style=british]{csquotes}%
  }%
}%
\makeatother

\begin{document}
\enquote{text}
\end{document}  
```

samcarter

You could also be all modern and use this new hook thingy like in https://github.com/josephwright/beamer/blob/bdc36d143eedafc33615fcd6d0a0beb7f1223253/base/beamerbasecompatibility.sty#L58-L60 Maybe someone more familiar with this can write up an answer about this.

samcarter replying to निरंजन

About the @ stuff: if latex loads a package, it makes @ automatically a letter, that's why you don't need `\makeatletter ... \makeatother` in your .sty file. I think in the past it would actually be an error to have them in the sty file because it would cause problems with packages loaded after it, nowadays they are just unnecessary most of the time.

निरंजन

The only difference in the code given above and the code given in the question was `\makeat...` commands. I had heard that these commands are not necessary while writing packages/classes; hence I avoided them, but adding them too doesn't work.

निरंजन

And surprisingly this works -

```
\documentclass{article}
\usepackage{marathi}
\makeatletter
\@ifpackageloaded{csquotes}{}{%
  \RequirePackage[style=british]{csquotes}%
}
\makeatother

\begin{document}
\enquote{text}
\end{document}
```

2 Answers