[hermes] Take responsibility for all terminal UI

tools/hermes/Cargo.toml

@@ -23,6 +23,8 @@ syn = { version = "2.0.114", features = ["full", "visit", "extra-traits", "parsi
 quote = "1.0"
 thiserror = "2.0.18"
 walkdir = "2.5.0"
+indicatif = { version = "0.18.3", features = ["improved_unicode"] }
+console = "0.16.2"
 
 [dev-dependencies]
 syn = { version = "2.0.114", features = ["printing", "full", "visit", "extra-traits", "parsing"] }
@@ -35,6 +37,8 @@ datatest-stable = "0.3.3"
 serde = { version = "1.0", features = ["derive"] }
 toml = "0.8"
 which = "6.0"
+regex.workspace = true
+strip-ansi-escapes = "0.2.1"
 
 [[test]]
 name = "integration"

tools/hermes/src/charon.rs

@@ -1,6 +1,10 @@
-use std::process::Command;
+use std::{
+    io::{BufRead, BufReader},
+    process::Command,
+};
 
 use anyhow::{bail, Context as _, Result};
+use cargo_metadata::{diagnostic::DiagnosticLevel, Message};
 
 use crate::{
     resolve::{Args, HermesTargetKind, Roots},
@@ -39,6 +43,9 @@ pub fn run_charon(args: &Args, roots: &Roots, packages: &[HermesArtifact]) -> Re
         // Separator for the underlying cargo command
         cmd.arg("--");
 
+        // Ensure cargo emits json msgs which charon-driver natively generates
+        cmd.arg("--message-format=json");
+
         cmd.arg("--manifest-path").arg(&artifact.shadow_manifest_path);
 
         match artifact.target_kind {
@@ -77,9 +84,95 @@ pub fn run_charon(args: &Args, roots: &Roots, packages: &[HermesArtifact]) -> Re
 
         log::debug!("Command: {:?}", cmd);
 
-        let status = cmd.status().context("Failed to execute charon")?;
+        cmd.stdout(std::process::Stdio::piped());
+        cmd.stderr(std::process::Stdio::piped());
+        let mut child = cmd.spawn().context("Failed to spawn charon")?;
+
+        let mut output_error = false;
+
+        let safety_buffer = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
+        let safety_buffer_clone = std::sync::Arc::clone(&safety_buffer);
+        if let Some(stderr) = child.stderr.take() {
+            std::thread::spawn(move || {
+                use std::io::{BufRead, BufReader};
+                let reader = BufReader::new(stderr);
+                for line in reader.lines() {
+                    if let Ok(line) = line {
+                        if let Ok(mut buf) = safety_buffer_clone.lock() {
+                            buf.push(line);
+                        }
+                    }
+                }
+            });
+        }
 
-        if !status.success() {
+        let pb = indicatif::ProgressBar::new_spinner();
+        pb.set_style(
+            indicatif::ProgressStyle::default_spinner().template("{spinner:.green} {msg}").unwrap(),
+        );
+        pb.enable_steady_tick(std::time::Duration::from_millis(100));
+        pb.set_message("Compiling...");
+
+        if let Some(stdout) = child.stdout.take() {
+            let reader = BufReader::new(stdout);
+
+            let mut mapper = crate::diagnostics::DiagnosticMapper::new(
+                artifact.shadow_manifest_path.parent().unwrap().to_path_buf(),
+                roots.workspace.clone(),
+            );
+
+            for line in reader.lines() {
+                if let Ok(line) = line {
+                    if let Ok(msg) = serde_json::from_str::<cargo_metadata::Message>(&line) {
+                        match msg {
+                            Message::CompilerArtifact(a) => {
+                                pb.set_message(format!("Compiling {}", a.target.name));
+                            }
+                            Message::CompilerMessage(msg) => {
+                                pb.suspend(|| {
+                                    mapper.render_miette(&msg.message, |s| eprintln!("{}", s));
+                                });
+                                if matches!(
+                                    msg.message.level,
+                                    DiagnosticLevel::Error | DiagnosticLevel::Ice
+                                ) {
+                                    output_error = true;
+                                }
+                            }
+                            Message::TextLine(t) => {
+                                if let Ok(mut buf) = safety_buffer.lock() {
+                                    buf.push(t);
+                                }
+                            }
+                            _ => {}
+                        }
+                    } else {
+                        if let Ok(mut buf) = safety_buffer.lock() {
+                            buf.push(line);
+                        }
+                    }
+                }
+            }
+        }
+
+        pb.finish_and_clear();
+
+        let status = child.wait().context("Failed to wait for charon")?;
+
+        // FIXME: There's a subtle edge case here – if we get error output AND
+        // Rustc ICE's, there's a good chance that the JSON error messages we
+        // print won't include all relevant information – some will be printed
+        // via stderr. In this case, `output_error = true` and so we bail and
+        // discard stderr, which will swallow information from the user.
+        if output_error {
+            bail!("Diagnostic error in charon");
+        } else if !status.success() {
+            // "Silent Death" dump
+            if let Ok(buf) = safety_buffer.lock() {
+                for line in buf.iter() {
+                    eprintln!("{}", line);
+                }
+            }
             bail!("Charon failed with status: {}", status);
         }
     }

tools/hermes/src/diagnostics.rs

@@ -0,0 +1,180 @@
+use std::{
+    collections::HashMap,
+    fs,
+    path::{Path, PathBuf},
+};
+
+use cargo_metadata::diagnostic::{Diagnostic, DiagnosticLevel, DiagnosticSpan};
+use miette::{NamedSource, Report, SourceOffset};
+use thiserror::Error;
+
+pub struct DiagnosticMapper {
+    shadow_root: PathBuf,
+    user_root: PathBuf,
+    user_root_canonical: PathBuf,
+    source_cache: HashMap<PathBuf, String>,
+}
+
+#[derive(Error, Debug)]
+#[error("{message}")]
+struct MappedError {
+    message: String,
+    src: NamedSource<String>,
+    labels: Vec<miette::LabeledSpan>,
+    help: Option<String>,
+    related: Vec<MappedError>,
+}
+
+impl miette::Diagnostic for MappedError {
+    fn source_code(&self) -> Option<&dyn miette::SourceCode> {
+        Some(&self.src)
+    }
+
+    fn labels(&self) -> Option<Box<dyn Iterator<Item = miette::LabeledSpan> + '_>> {
+        if self.labels.is_empty() {
+            None
+        } else {
+            Some(Box::new(self.labels.iter().cloned()))
+        }
+    }
+
+    fn help(&self) -> Option<Box<dyn std::fmt::Display + '_>> {
+        self.help.as_ref().map(|h| Box::new(h.clone()) as Box<dyn std::fmt::Display>)
+    }
+
+    fn related<'a>(&'a self) -> Option<Box<dyn Iterator<Item = &'a dyn miette::Diagnostic> + 'a>> {
+        if self.related.is_empty() {
+            None
+        } else {
+            let iter = self.related.iter().map(|e| e as &dyn miette::Diagnostic);
+            Some(Box::new(iter))
+        }
+    }
+}
+
+impl DiagnosticMapper {
+    pub fn new(shadow_root: PathBuf, user_root: PathBuf) -> Self {
+        let user_root_canonical =
+            fs::canonicalize(&user_root).unwrap_or_else(|_| user_root.clone());
+        Self { shadow_root, user_root, user_root_canonical, source_cache: HashMap::new() }
+    }
+
+    pub fn map_path(&self, path: &Path) -> Option<PathBuf> {
+        let mut p = path.to_path_buf();
+        if p.is_relative() {
+            p = self.user_root.join(p);
+        }
+
+        // Strategy A: Starts with shadow_root
+        if let Ok(suffix) = p.strip_prefix(&self.shadow_root) {
+            return Some(self.user_root.join(suffix));
+        }
+
+        // Strategy B: Starts with user_root or user_root_canonical
+        if p.starts_with(&self.user_root) || p.starts_with(&self.user_root_canonical) {
+            return Some(p);
+        }
+
+        None
+    }
+
+    fn get_source(&mut self, path: &Path) -> Option<String> {
+        if let Some(src) = self.source_cache.get(path) {
+            return Some(src.clone());
+        }
+        if let Ok(src) = fs::read_to_string(path) {
+            self.source_cache.insert(path.to_path_buf(), src.clone());
+            Some(src)
+        } else {
+            None
+        }
+    }
+
+    pub fn render_miette<F>(&mut self, diag: &Diagnostic, mut printer: F)
+    where
+        F: FnMut(String),
+    {
+        let mut mapped_paths_and_spans: HashMap<PathBuf, Vec<&DiagnosticSpan>> = HashMap::new();
+
+        // 1) Group spans by mapped path
+        for s in &diag.spans {
+            let p = PathBuf::from(&s.file_name);
+            if let Some(mapped_path) = self.map_path(&p) {
+                mapped_paths_and_spans.entry(mapped_path).or_default().push(s);
+            }
+        }
+
+        // Check children for help messages
+        let mut help_msg = None;
+        for child in &diag.children {
+            if child.level == DiagnosticLevel::Help {
+                help_msg = Some(child.message.clone());
+            }
+        }
+
+        if !mapped_paths_and_spans.is_empty() {
+            // Find the path that contains the primary span, or just take the first one
+            let primary_path = diag
+                .spans
+                .iter()
+                .find(|s| s.is_primary)
+                .and_then(|s| self.map_path(&PathBuf::from(&s.file_name)))
+                .or_else(|| mapped_paths_and_spans.keys().next().cloned());
+
+            if let Some(main_path) = primary_path {
+                let mut all_errors = Vec::new();
+
+                // Sort the paths to have the primary path first
+                let mut paths: Vec<PathBuf> = mapped_paths_and_spans.keys().cloned().collect();
+                paths.sort_by_key(|p| p != &main_path);
+
+                for p in paths {
+                    if let Some(src) = self.get_source(&p) {
+                        let mut labels = Vec::new();
+                        for s in mapped_paths_and_spans.get(&p).unwrap() {
+                            let label_text = s.label.clone().unwrap_or_default();
+                            let start = s.byte_start as usize;
+                            let len = (s.byte_end - s.byte_start) as usize;
+                            if start <= src.len() && start + len <= src.len() {
+                                let offset = SourceOffset::from(start);
+                                labels.push(miette::LabeledSpan::new(
+                                    Some(label_text),
+                                    offset.offset(),
+                                    len,
+                                ));
+                            }
+                        }
+
+                        let err = MappedError {
+                            message: if p == main_path {
+                                diag.message.clone()
+                            } else {
+                                format!("related to: {}", p.display())
+                            },
+                            src: NamedSource::new(p.to_string_lossy(), src),
+                            labels,
+                            help: if p == main_path { help_msg.clone() } else { None },
+                            related: Vec::new(),
+                        };
+                        all_errors.push(err);
+                    }
+                }
+
+                if !all_errors.is_empty() {
+                    let mut main_err = all_errors.remove(0);
+                    main_err.related = all_errors;
+                    printer(format!("{:?}", Report::new(main_err)));
+                    return;
+                }
+            }
+        }
+
+        // If we get here, no span was successfully mapped
+        let prefix = match diag.level {
+            DiagnosticLevel::Error | DiagnosticLevel::Ice => "[External Error]",
+            DiagnosticLevel::Warning => "[External Warning]",
+            _ => "[External Info]",
+        };
+        printer(format!("{} {}", prefix, diag.message));
+    }
+}

tools/hermes/src/main.rs

@@ -1,4 +1,5 @@
 mod charon;
+mod diagnostics;
 mod errors;
 mod parse;
 mod resolve;