From 8c4726b55e829d6e9bd1000f96a7f78c46c18546 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 18 Feb 2022 11:34:53 +0000
Subject: [PATCH] Provide error reporter and use it in the arti binary

---
 Cargo.lock                     |  1 +
 crates/arti/Cargo.toml         |  1 +
 crates/arti/src/main.rs        |  6 ++++-
 crates/tor-error/src/lib.rs    |  3 +++
 crates/tor-error/src/report.rs | 40 ++++++++++++++++++++++++++++++++++
 5 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 crates/tor-error/src/report.rs

diff --git a/Cargo.lock b/Cargo.lock
index d8aba3640..ef38e6d3b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -86,6 +86,7 @@ dependencies = [
  "rlimit",
  "serde",
  "tokio",
+ "tor-error",
  "tor-rtcompat",
  "tor-socksproto",
  "tracing",
diff --git a/crates/arti/Cargo.toml b/crates/arti/Cargo.toml
index f8d30d00a..7f1e39273 100644
--- a/crates/arti/Cargo.toml
+++ b/crates/arti/Cargo.toml
@@ -21,6 +21,7 @@ journald = [ "tracing-journald" ]
 
 [dependencies]
 arti-client = { package="arti-client", path = "../arti-client", version = "0.0.4", default-features=false}
+tor-error = { path="../tor-error", version = "0.0.1", default-features=false }
 tor-rtcompat = { path="../tor-rtcompat", version = "0.0.4", default-features=false }
 tor-socksproto = { path="../tor-socksproto", version = "0.0.3"}
 arti-config = { path="../arti-config", version = "0.0.4"}
diff --git a/crates/arti/src/main.rs b/crates/arti/src/main.rs
index 0bce0c4a4..d5fb444ad 100644
--- a/crates/arti/src/main.rs
+++ b/crates/arti/src/main.rs
@@ -125,7 +125,11 @@ async fn run<R: Runtime>(
     )
 }
 
-fn main() -> Result<()> {
+fn main() {
+    main_main().unwrap_or_else(tor_error::report_and_exit)
+}
+
+fn main_main() -> Result<()> {
     // We describe a default here, rather than using `default()`, because the
     // correct behavior is different depending on whether the filename is given
     // explicitly or not.
diff --git a/crates/tor-error/src/lib.rs b/crates/tor-error/src/lib.rs
index d3e50a3a2..25c4daf91 100644
--- a/crates/tor-error/src/lib.rs
+++ b/crates/tor-error/src/lib.rs
@@ -41,6 +41,9 @@ use derive_more::Display;
 mod internal;
 pub use internal::*;
 
+mod report;
+pub use report::*;
+
 mod truncated;
 pub use truncated::*;
 
diff --git a/crates/tor-error/src/report.rs b/crates/tor-error/src/report.rs
new file mode 100644
index 000000000..8ebcde671
--- /dev/null
+++ b/crates/tor-error/src/report.rs
@@ -0,0 +1,40 @@
+//! The Report type which reports errors nicely
+
+use std::fmt::{self, Debug, Display};
+
+/// Wraps any Error, providing a nicely-reporting Display impl
+#[derive(Debug, Copy, Clone)]
+pub struct Report<E>(pub E);
+
+impl<E> Display for Report<E> where E: AsRef<dyn std::error::Error> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fn inner(mut e: &dyn std::error::Error, f: &mut fmt::Formatter) -> fmt::Result {
+            if let Some(progname) = std::env::args().next() {
+                write!(f, "{}: ", progname)?;
+            }
+            write!(f, "error")?;
+            let mut last = String::new();
+            loop {
+                let this = e.to_string();
+                if ! last.contains(&this) {
+                    write!(f, ": {}", &this)?;
+                }
+                last = this;
+
+                if let Some(ne) = e.source() {
+                    e = ne
+                } else {
+                    break
+                }
+            }
+            Ok(())
+        }
+
+        inner(self.0.as_ref(), f)
+    }
+}
+
+pub fn report_and_exit<E, R>(e: E) -> R where E: AsRef<dyn std::error::Error> {
+    eprintln!("{}", Report(e));
+    std::process::exit(127)
+}