Auto merge of rust-lang#78429 - casey:doctest-attribute-splitting, r=jyn514

[librustdoc] Only split lang string on `,`, ` `, and `\t`

Split markdown lang strings into tokens on `,`.

The previous behavior was to split lang strings into tokens on any
character that wasn't a `_`, `_`, or alphanumeric.

This is a potentially breaking change, so please scrutinize! See discussion in rust-lang#78344.

I noticed some test cases that made me wonder if there might have been some reason for the original behavior:

```
t("{.no_run .example}", false, true, Ignore::None, true, false, false, false, v(), None);
t("{.sh .should_panic}", true, false, Ignore::None, false, false, false, false, v(), None);
t("{.example .rust}", false, false, Ignore::None, true, false, false, false, v(), None);
t("{.test_harness .rust}", false, false, Ignore::None, true, true, false, false, v(), None);
```

It seemed pretty peculiar to specifically test lang strings in braces, with all the tokens prefixed by `.`.

I did some digging, and it looks like the test cases were added way back in [this commit from 2014](rust-lang@3fef7a74ca9a) by `@skade.`

It looks like they were added just to make sure that the splitting was permissive, and aren't testing that those strings in particular are accepted.

Closes rust-lang#78344.

Author: bors

core/src/option.rs

@@ -336,7 +336,7 @@ impl<T> Option<T> {
     /// assert_eq!(x.expect("fruits are healthy"), "value");
     /// ```
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Option<&str> = None;
     /// x.expect("fruits are healthy"); // panics with `fruits are healthy`
     /// ```
@@ -372,7 +372,7 @@ impl<T> Option<T> {
     /// assert_eq!(x.unwrap(), "air");
     /// ```
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Option<&str> = None;
     /// assert_eq!(x.unwrap(), "air"); // fails
     /// ```
@@ -1114,7 +1114,7 @@ impl<T: fmt::Debug> Option<T> {
     /// }
     /// ```
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// #![feature(option_expect_none)]
     ///
     /// use std::collections::HashMap;
@@ -1156,7 +1156,7 @@ impl<T: fmt::Debug> Option<T> {
     /// }
     /// ```
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// #![feature(option_unwrap_none)]
     ///
     /// use std::collections::HashMap;

core/src/result.rs

@@ -112,7 +112,7 @@
 //! assert success with [`expect`]. This will panic if the
 //! write fails, providing a marginally useful message indicating why:
 //!
-//! ```{.no_run}
+//! ```no_run
 //! use std::fs::File;
 //! use std::io::prelude::*;
 //!
@@ -122,7 +122,7 @@
 //!
 //! You might also simply assert success:
 //!
-//! ```{.no_run}
+//! ```no_run
 //! # use std::fs::File;
 //! # use std::io::prelude::*;
 //! # let mut file = File::create("valuable_data.txt").unwrap();
@@ -984,7 +984,7 @@ impl<T, E: fmt::Debug> Result<T, E> {
     ///
     /// Basic usage:
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Result<u32, &str> = Err("emergency failure");
     /// x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
     /// ```
@@ -1024,7 +1024,7 @@ impl<T, E: fmt::Debug> Result<T, E> {
     /// assert_eq!(x.unwrap(), 2);
     /// ```
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Result<u32, &str> = Err("emergency failure");
     /// x.unwrap(); // panics with `emergency failure`
     /// ```
@@ -1052,7 +1052,7 @@ impl<T: fmt::Debug, E> Result<T, E> {
     ///
     /// Basic usage:
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Result<u32, &str> = Ok(10);
     /// x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
     /// ```
@@ -1075,7 +1075,7 @@ impl<T: fmt::Debug, E> Result<T, E> {
     ///
     /// # Examples
     ///
-    /// ```{.should_panic}
+    /// ```should_panic
     /// let x: Result<u32, &str> = Ok(2);
     /// x.unwrap_err(); // panics with `2`
     /// ```