Fix formatting generation for rustdoc code examples

[GuillaumeGomez]

Now, when clicking on the Run link in the docs, the code is indented if it is put in a main function (I couldn't stand the horrible output we currently have).

r? @steveklabnik

[ollie27]

This looks like it's essentially reverting #33512 and so is bringing back #25944.

[GuillaumeGomez]

I guess? (I didn't know it was done "correctly" before.)

[steveklabnik]

/cc @rust-lang/tools

[nrc]

Is this just a matter of inserting \ into multi-line string lits?

[GuillaumeGomez]

@nrc: I didn't understand your comment. Why are talking about \?

[nrc]

@GuillaumeGomez I might be mistaken, but my understanding was that #25944 is only an issue with multiline string lits, and that if one does

"dfasd asdfasdf \
 sdfsdf dsfsdf"

rather than

"dfasd asdfasdf
 sdfsdf dsfsdf"

Then the indentation change should not be a problem.

[GuillaumeGomez]

Ah right. Then no, I don't see why it would break it.

[brson]

sgtm

[GuillaumeGomez]

Any news about this?

[alexcrichton]

I agree with @ollie27 that this seems like it'd be regressing the fix from earlier, and as a result may not be worth it as a standalone feature.

Perhaps we could send requests to playpen which auto-format the code?

[GuillaumeGomez]

@alexcrichton: If it's done then I'll even remove the indent/backlines when creating the URL.

[frewsxcv]

Is it possible to separate the String of code that generates the URL from the String of code that gets doc-tested? Then the former could receive appropriate indentation without affecting the latter.

[steveklabnik]

So, what's the state of this PR?

[GuillaumeGomez]

@steveklabnik: Still waiting for @alexcrichton update on play.rust-lang.org I think?

[alexcrichton]

Sorry, but what's supposed to happen?

[frewsxcv]

In my opinion, I don't think we should auto format code when loading the playpen. This seems like a bug with URL generation with rustdoc.

[GuillaumeGomez]

@alexcrichton: You said:

Perhaps we could send requests to playpen which auto-format the code?

So I thought something was moving in this way. Sorry if I misunderstood.

@frewsxcv: So my current PR is the "correct" way to do it I guess? :p

[alexcrichton]

@GuillaumeGomez oh no I wasn't actually planning on making any changes myself, no.

@frewsxcv the problem is that this documentation:

/// ```
/// "foo \
/// bar"
/// ```

changes meaning depending on whether rustdoc snippets are auto-indented. We can auto-indent, but it changes the meaning of that string literal (the original bug)

[steveklabnik]

It looks like we're not going to accept this, so I'm giving it a close. Let me know if that reading is wrong.