feat(stream): Allow styled panic messages

crates/anstyle-stream/src/auto.rs

@@ -28,6 +28,28 @@ where
     #[cfg(feature = "auto")]
     #[inline]
     pub fn new(raw: S, choice: ColorChoice) -> Self {
+        match choice {
+            ColorChoice::Auto => Self::auto(raw),
+            ColorChoice::AlwaysAnsi => Self::always_ansi(raw),
+            ColorChoice::Always => Self::always(raw),
+            ColorChoice::Never => Self::never(raw),
+        }
+    }
+
+    /// Auto-adapt for the stream's capabilities
+    #[cfg(feature = "auto")]
+    #[inline]
+    pub fn auto(raw: S) -> Self {
+        let choice = Self::choice(&raw);
+        debug_assert_ne!(choice, ColorChoice::Auto);
+        Self::new(raw, choice)
+    }
+
+    /// Report the desired choice for the given stream
+    #[cfg(feature = "auto")]
+    #[inline]
+    pub fn choice(raw: &S) -> ColorChoice {
+        let choice = concolor_override::get();
         match choice {
             ColorChoice::Auto => {
                 let clicolor = concolor_query::clicolor();
@@ -41,24 +63,15 @@ where
                         || concolor_query::is_ci())
                     || concolor_query::clicolor_force()
                 {
-                    Self::always(raw)
+                    ColorChoice::Always
                 } else {
-                    Self::never(raw)
+                    ColorChoice::Never
                 }
             }
-            ColorChoice::AlwaysAnsi => Self::always_ansi(raw),
-            ColorChoice::Always => Self::always(raw),
-            ColorChoice::Never => Self::never(raw),
+            ColorChoice::AlwaysAnsi | ColorChoice::Always | ColorChoice::Never => choice,
         }
     }
 
-    /// Auto-adapt for the stream's capabilities
-    #[cfg(feature = "auto")]
-    #[inline]
-    pub fn auto(raw: S) -> Self {
-        Self::new(raw, concolor_override::get())
-    }
-
     /// Force ANSI escape codes to be passed through as-is, no matter what the inner `Write`
     /// supports.
     #[inline]

crates/anstyle-stream/src/macros.rs

@@ -214,3 +214,100 @@ macro_rules! eprintln {
         }
     }};
 }
+
+/// Panics the current thread.
+///
+/// This allows a program to terminate immediately and provide feedback
+/// to the caller of the program.
+///
+/// This macro is the perfect way to assert conditions in example code and in
+/// tests. `panic!` is closely tied with the `unwrap` method of both
+/// [`Option`][ounwrap] and [`Result`][runwrap] enums. Both implementations call
+/// `panic!` when they are set to [`None`] or [`Err`] variants.
+///
+/// When using `panic!()` you can specify a string payload, that is built using
+/// the [`format!`] syntax. That payload is used when injecting the panic into
+/// the calling Rust thread, causing the thread to panic entirely.
+///
+/// The behavior of the default `std` hook, i.e. the code that runs directly
+/// after the panic is invoked, is to print the message payload to
+/// `stderr` along with the file/line/column information of the `panic!()`
+/// call. You can override the panic hook using [`std::panic::set_hook()`].
+/// Inside the hook a panic can be accessed as a `&dyn Any + Send`,
+/// which contains either a `&str` or `String` for regular `panic!()` invocations.
+/// To panic with a value of another other type, [`panic_any`] can be used.
+///
+/// See also the macro [`compile_error!`], for raising errors during compilation.
+///
+/// # When to use `panic!` vs `Result`
+///
+/// The Rust language provides two complementary systems for constructing /
+/// representing, reporting, propagating, reacting to, and discarding errors. These
+/// responsibilities are collectively known as "error handling." `panic!` and
+/// `Result` are similar in that they are each the primary interface of their
+/// respective error handling systems; however, the meaning these interfaces attach
+/// to their errors and the responsibilities they fulfill within their respective
+/// error handling systems differ.
+///
+/// The `panic!` macro is used to construct errors that represent a bug that has
+/// been detected in your program. With `panic!` you provide a message that
+/// describes the bug and the language then constructs an error with that message,
+/// reports it, and propagates it for you.
+///
+/// `Result` on the other hand is used to wrap other types that represent either
+/// the successful result of some computation, `Ok(T)`, or error types that
+/// represent an anticipated runtime failure mode of that computation, `Err(E)`.
+/// `Result` is used alongside user defined types which represent the various
+/// anticipated runtime failure modes that the associated computation could
+/// encounter. `Result` must be propagated manually, often with the the help of the
+/// `?` operator and `Try` trait, and they must be reported manually, often with
+/// the help of the `Error` trait.
+///
+/// For more detailed information about error handling check out the [book] or the
+/// [`std::result`] module docs.
+///
+/// [ounwrap]: Option::unwrap
+/// [runwrap]: Result::unwrap
+/// [`std::panic::set_hook()`]: ../std/panic/fn.set_hook.html
+/// [`panic_any`]: ../std/panic/fn.panic_any.html
+/// [`Box`]: ../std/boxed/struct.Box.html
+/// [`Any`]: crate::any::Any
+/// [`format!`]: ../std/macro.format.html
+/// [book]: ../book/ch09-00-error-handling.html
+/// [`std::result`]: ../std/result/index.html
+///
+/// # Current implementation
+///
+/// If the main thread panics it will terminate all your threads and end your
+/// program with code `101`.
+///
+/// # Examples
+///
+/// ```should_panic
+/// # #![allow(unreachable_code)]
+/// use anstyle_stream::panic;
+/// panic!();
+/// panic!("this is a terrible mistake!");
+/// panic!("this is a {} {message}", "fancy", message = "message");
+/// ```
+#[cfg(feature = "auto")]
+#[macro_export]
+macro_rules! panic {
+    () => {
+        ::std::panic!()
+    };
+    ($($arg:tt)*) => {{
+        use std::io::Write as _;
+
+        let panic_stream = std::io::stderr();
+        let choice = $crate::AutoStream::choice(&panic_stream);
+        let buffer = $crate::Buffer::new();
+        let mut stream = $crate::AutoStream::new(buffer, choice);
+        // Ignore errors rather than panic
+        let _ = ::std::write!(&mut stream, $($arg)*);
+        let buffer = stream.into_inner();
+        // Should be UTF-8 but not wanting to panic
+        let buffer = String::from_utf8_lossy(buffer.as_bytes()).into_owned();
+        ::std::panic!("{}", buffer)
+    }};
+}