feat!: Set up human_panic in hugr-cli

hugr-cli/Cargo.toml

@@ -26,6 +26,7 @@ anyhow.workspace = true
 thiserror.workspace = true
 tracing = "0.1.41"
 tracing-subscriber = { version = "0.3.19", features = ["fmt"] }
+human-panic = "2"
 
 [lints]
 workspace = true
@@ -37,6 +38,9 @@ workspace = true
 enum_missing = "warn"
 struct_missing = "warn"
 
+[features]
+panic-test = []
+
 [dev-dependencies]
 assert_cmd = { workspace = true }
 assert_fs = { workspace = true }

hugr-cli/src/main.rs

@@ -9,6 +9,15 @@ use hugr_cli::{CliArgs, CliCommand};
 use tracing::{error, metadata::LevelFilter};
 
 fn main() {
+    // Enable human-panic for release builds, or when tests force it via env.
+    if cfg!(not(debug_assertions)) || std::env::var_os("FORCE_HUMAN_PANIC").is_some() {
+        human_panic::setup_panic!();
+    }
+
+    // Test-only panic trigger (harmless in production; only fires if env is set).
+    if std::env::var_os("PANIC_FOR_TESTS").is_some() {
+        panic!("triggered by test");
+    }
     let cli_args = CliArgs::parse();
 
     let level = match cli_args.verbose.filter() {

hugr-cli/tests/human_panic_integration.rs

@@ -0,0 +1,64 @@
+//! Integration test for `human-panic`.
+//!
+//! Builds the release binary with the `panic-test` feature, runs it with a
+//! test-only panic trigger and an isolated temp dir, asserts the banner,
+//! and verifies a TOML report is written. Temp dir is removed at the end.
+
+//! Black-box integration test for `human-panic`.
+
+use predicates::str::contains; // for cargo_bin()
+use std::process::Command;
+use tempfile::TempDir;
+
+#[test]
+fn human_panic_writes_report() {
+    // Isolated temp dir for the crash report.
+    let tmp = TempDir::new().expect("create tempdir");
+    let tmp_path = tmp.path();
+
+    // Run the release CLI binary from the workspace root.
+    // No features needed: main() installs human-panic in release builds.
+    let mut cmd = Command::new("cargo");
+    cmd.args([
+        "run",
+        "--release",
+        "-p",
+        "hugr-cli",
+        "--bin",
+        "hugr",
+        "--", // end cargo args; program args would follow
+    ]);
+
+    // Isolate temp location & trigger the test panic in the child process.
+    if cfg!(windows) {
+        cmd.env("TEMP", tmp_path).env("TMP", tmp_path);
+    } else {
+        cmd.env("TMPDIR", tmp_path);
+    }
+    cmd.env("PANIC_FOR_TESTS", "1");
+
+    // Expect non-zero exit and the banner on stderr (release only).
+    assert_cmd::Command::from_std(cmd)
+        .assert()
+        .failure()
+        .stderr(contains("Well, this is embarrassing."));
+
+    // Confirm a .toml report exists in our temp dir.
+    let made_report = std::fs::read_dir(tmp_path)
+        .unwrap()
+        .filter_map(Result::ok)
+        .any(|e| {
+            e.path()
+                .extension()
+                .and_then(|ext| ext.to_str())
+                .is_some_and(|ext| ext.eq_ignore_ascii_case("toml"))
+        });
+    assert!(
+        made_report,
+        "expected a human-panic report in {:?}",
+        tmp_path
+    );
+
+    // Explicit cleanup; surface any removal errors.
+    tmp.close().expect("failed to remove temp dir");
+}