feat: Add unstable rustc-unicode flag

src/cargo/core/compiler/mod.rs

@@ -1095,11 +1095,14 @@ fn add_error_format_and_color(build_runner: &BuildRunner<'_, '_>, cmd: &mut Proc
     cmd.arg("--error-format=json");
     let mut json = String::from("--json=diagnostic-rendered-ansi,artifacts,future-incompat");
 
-    match build_runner.bcx.build_config.message_format {
-        MessageFormat::Short | MessageFormat::Json { short: true, .. } => {
-            json.push_str(",diagnostic-short");
-        }
-        _ => {}
+    if let MessageFormat::Short | MessageFormat::Json { short: true, .. } =
+        build_runner.bcx.build_config.message_format
+    {
+        json.push_str(",diagnostic-short");
+    } else if build_runner.bcx.gctx.shell().err_unicode()
+        && build_runner.bcx.gctx.cli_unstable().rustc_unicode
+    {
+        json.push_str(",diagnostic-unicode");
     }
 
     if enable_timings {

src/cargo/core/features.rs

@@ -881,6 +881,7 @@ unstable_cli_options!(
     public_dependency: bool = ("Respect a dependency's `public` field in Cargo.toml to control public/private dependencies"),
     publish_timeout: bool = ("Enable the `publish.timeout` key in .cargo/config.toml file"),
     root_dir: Option<PathBuf> = ("Set the root directory relative to which paths are printed (defaults to workspace root)"),
+    rustc_unicode: bool = ("Enable `rustc`'s unicode error format in Cargo's error messages"),
     rustdoc_depinfo: bool = ("Use dep-info files in rustdoc rebuild detection"),
     rustdoc_map: bool = ("Allow passing external documentation mappings to rustdoc"),
     rustdoc_scrape_examples: bool = ("Allows Rustdoc to scrape code examples from reverse-dependencies"),
@@ -1411,6 +1412,7 @@ impl CliUnstable {
             "trim-paths" => self.trim_paths = parse_empty(k, v)?,
             "publish-timeout" => self.publish_timeout = parse_empty(k, v)?,
             "root-dir" => self.root_dir = v.map(|v| v.into()),
+            "rustc-unicode" => self.rustc_unicode = parse_empty(k, v)?,
             "rustdoc-depinfo" => self.rustdoc_depinfo = parse_empty(k, v)?,
             "rustdoc-map" => self.rustdoc_map = parse_empty(k, v)?,
             "rustdoc-scrape-examples" => self.rustdoc_scrape_examples = parse_empty(k, v)?,

src/cargo/core/shell.rs

@@ -2,6 +2,7 @@ use std::fmt;
 use std::io::IsTerminal;
 use std::io::prelude::*;
 
+use annotate_snippets::renderer::DecorStyle;
 use annotate_snippets::{Renderer, Report};
 use anstream::AutoStream;
 use anstyle::Style;
@@ -57,6 +58,7 @@ impl Shell {
                 stdout_unicode: supports_unicode(&std::io::stdout()),
                 stderr_unicode: supports_unicode(&std::io::stderr()),
                 stderr_term_integration: supports_term_integration(&std::io::stderr()),
+                unstable_flags_rustc_unicode: false,
             },
             verbosity: Verbosity::Verbose,
             needs_clear: false,
@@ -380,6 +382,27 @@ impl Shell {
         Some(url)
     }
 
+    fn unstable_flags_rustc_unicode(&self) -> bool {
+        match &self.output {
+            ShellOut::Write(_) => false,
+            ShellOut::Stream {
+                unstable_flags_rustc_unicode,
+                ..
+            } => *unstable_flags_rustc_unicode,
+        }
+    }
+
+    pub(crate) fn set_unstable_flags_rustc_unicode(&mut self, yes: bool) -> CargoResult<()> {
+        if let ShellOut::Stream {
+            unstable_flags_rustc_unicode,
+            ..
+        } = &mut self.output
+        {
+            *unstable_flags_rustc_unicode = yes;
+        }
+        Ok(())
+    }
+
     /// Prints a message to stderr and translates ANSI escape code into console colors.
     pub fn print_ansi_stderr(&mut self, message: &[u8]) -> CargoResult<()> {
         if self.needs_clear {
@@ -419,7 +442,15 @@ impl Shell {
             .err_width()
             .diagnostic_terminal_width()
             .unwrap_or(annotate_snippets::renderer::DEFAULT_TERM_WIDTH);
-        let rendered = Renderer::styled().term_width(term_width).render(report);
+        let decor_style = if self.err_unicode() && self.unstable_flags_rustc_unicode() {
+            DecorStyle::Unicode
+        } else {
+            DecorStyle::Ascii
+        };
+        let rendered = Renderer::styled()
+            .term_width(term_width)
+            .decor_style(decor_style)
+            .render(report);
         self.err().write_all(rendered.as_bytes())?;
         self.err().write_all(b"\n")?;
         Ok(())
@@ -446,6 +477,7 @@ enum ShellOut {
         stdout_unicode: bool,
         stderr_unicode: bool,
         stderr_term_integration: bool,
+        unstable_flags_rustc_unicode: bool,
     },
 }
 

src/cargo/util/context/mod.rs

@@ -1174,6 +1174,9 @@ impl GlobalContext {
         let cli_target_dir = target_dir.as_ref().map(|dir| Filesystem::new(dir.clone()));
         self.target_dir = cli_target_dir;
 
+        self.shell()
+            .set_unstable_flags_rustc_unicode(self.unstable_flags.rustc_unicode)?;
+
         Ok(())
     }
 

src/doc/src/reference/unstable.md

@@ -116,6 +116,7 @@ Each new feature described below should explain how to use it.
     * [unit-graph](#unit-graph) --- Emits JSON for Cargo's internal graph structure.
     * [`cargo rustc --print`](#rustc---print) --- Calls rustc with `--print` to display information from rustc.
     * [Build analysis](#build-analysis) --- Record and persist detailed build metrics across runs, with new commands to query past builds.
+    * [`rustc-unicode`](#rustc-unicode) --- Enables `rustc`'s unicode error format in Cargo's error messages 
 * Configuration
     * [config-include](#config-include) --- Adds the ability for config files to include other files.
     * [`cargo config`](#cargo-config) --- Adds a new subcommand for viewing config files.
@@ -2028,6 +2029,12 @@ cargo +nightly build --compile-time-deps -Z unstable-options
 cargo +nightly check --compile-time-deps --all-targets -Z unstable-options
 ```
 
+# `rustc-unicode`
+* Tracking Issue: [rust#148607](https://github.com/rust-lang/rust/issues/148607)
+
+Enable `rustc`'s unicode error format in Cargo's error messages
+
+
 # Stabilized and removed features
 
 ## Compile progress

tests/testsuite/lints/mod.rs

@@ -323,3 +323,42 @@ workspace = true
 "#]])
         .run();
 }
+
+#[cargo_test(nightly, reason = "-Zrustc-unicode is unstable")]
+fn unicode_report() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+cargo-features = ["test-dummy-unstable"]
+
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2015"
+authors = []
+im-a-teapot = true
+
+[lints.cargo]
+im_a_teapot = { level = "warn", priority = 10 }
+"#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("check -Zcargo-lints -Zrustc-unicode")
+        .masquerade_as_nightly_cargo(&["cargo-lints", "rustc-unicode", "test-dummy-unstable"])
+        .with_stderr_data(str![[r#"
+[WARNING] `im_a_teapot` is specified
+  ╭▸ Cargo.toml:9:1
+  │
+9 │ im-a-teapot = true
+  │ ━━━━━━━━━━━━━━━━━━
+  │
+  ╰ [NOTE] `cargo::im_a_teapot` is set to `warn` in `[lints]`
+[CHECKING] foo v0.0.1 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
+"#]])
+        .run();
+}

tests/testsuite/message_format.rs

@@ -162,6 +162,42 @@ failures:
 test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in [ELAPSED]s
 
 
+"#]])
+        .run();
+}
+
+#[cargo_test(nightly, reason = "-Zrustc-unicode is unstable")]
+fn cargo_passes_unicode_output() {
+    let foo = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.0.1"
+                edition = "2015"
+            "#,
+        )
+        .file(
+            "src/lib.rs",
+            "\
+mod tests {
+    #[test]
+    fn t1() {
+        use std::io;
+    }
+}
+            ",
+        )
+        .build();
+
+    foo.cargo("check -v -Zrustc-unicode")
+        .masquerade_as_nightly_cargo(&["rustc-unicode"])
+        .with_stderr_data(str![[r#"
+[CHECKING] foo v0.0.1 ([ROOT]/foo)
+[RUNNING] `rustc [..] --json=diagnostic-rendered-ansi,artifacts,future-incompat,diagnostic-unicode [..]`
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
 "#]])
         .run();
 }