fix(rustdoc): Color doctest errors

Author: Muscraft

compiler/rustc_errors/src/emitter.rs

@@ -3466,14 +3466,9 @@ impl Drop for Buffy {
 
 pub fn stderr_destination(color: ColorConfig) -> Destination {
     let buffer_writer = std::io::stderr();
-    let choice = color.to_color_choice();
     // We need to resolve `ColorChoice::Auto` before `Box`ing since
     // `ColorChoice::Auto` on `dyn Write` will always resolve to `Never`
-    let choice = if matches!(choice, ColorChoice::Auto) {
-        AutoStream::choice(&buffer_writer)
-    } else {
-        choice
-    };
+    let choice = get_stderr_color_choice(color, &buffer_writer);
     // On Windows we'll be performing global synchronization on the entire
     // system for emitting rustc errors, so there's no need to buffer
     // anything.
@@ -3488,6 +3483,11 @@ pub fn stderr_destination(color: ColorConfig) -> Destination {
     }
 }
 
+pub fn get_stderr_color_choice(color: ColorConfig, stderr: &std::io::Stderr) -> ColorChoice {
+    let choice = color.to_color_choice();
+    if matches!(choice, ColorChoice::Auto) { AutoStream::choice(stderr) } else { choice }
+}
+
 /// On Windows, BRIGHT_BLUE is hard to read on black. Use cyan instead.
 ///
 /// See #36178.

src/librustdoc/doctest/make.rs

@@ -8,8 +8,8 @@ use std::sync::Arc;
 use rustc_ast::token::{Delimiter, TokenKind};
 use rustc_ast::tokenstream::TokenTree;
 use rustc_ast::{self as ast, AttrStyle, HasAttrs, StmtKind};
-use rustc_errors::emitter::stderr_destination;
-use rustc_errors::{AutoStream, ColorConfig, DiagCtxtHandle};
+use rustc_errors::emitter::get_stderr_color_choice;
+use rustc_errors::{AutoStream, ColorChoice, ColorConfig, DiagCtxtHandle};
 use rustc_parse::lexer::StripTokens;
 use rustc_parse::new_parser_from_source_str;
 use rustc_session::parse::ParseSess;
@@ -446,7 +446,7 @@ fn parse_source(
     span: Span,
 ) -> Result<ParseSourceInfo, ()> {
     use rustc_errors::DiagCtxt;
-    use rustc_errors::emitter::{Emitter, HumanEmitter};
+    use rustc_errors::emitter::HumanEmitter;
     use rustc_span::source_map::FilePathMapping;
 
     let mut info =
@@ -458,9 +458,12 @@ fn parse_source(
 
     let sm = Arc::new(SourceMap::new(FilePathMapping::empty()));
     let translator = rustc_driver::default_translator();
-    info.supports_color =
-        HumanEmitter::new(stderr_destination(ColorConfig::Auto), translator.clone())
-            .supports_color();
+    let supports_color = match get_stderr_color_choice(ColorConfig::Auto, &std::io::stderr()) {
+        ColorChoice::Auto => unreachable!(),
+        ColorChoice::AlwaysAnsi | ColorChoice::Always => true,
+        ColorChoice::Never => false,
+    };
+    info.supports_color = supports_color;
     // Any errors in parsing should also appear when the doctest is compiled for real, so just
     // send all the errors that the parser emits directly into a `Sink` instead of stderr.
     let emitter = HumanEmitter::new(AutoStream::never(Box::new(io::sink())), translator);