Improve panic messaging and process behavior.

- Replaced main() to use custom panic hook
- Updated log formatting
- Switched to panic=abort, since we don't need to unwind now.
- Process will now abort if any thread panics.

CHANGELOG.md

@@ -4,6 +4,10 @@
 * Added `--watch` argument to `rojo build`. ([#284](https://github.com/rojo-rbx/rojo/pull/284))
 * Added dark theme support to plugin. ([#241](https://github.com/rojo-rbx/rojo/issues/241))
 * Simplified filesystem access code dramatically.
+* Improved error reporting and logging across the board.
+    * Log messages have a less noisy prefix.
+    * Any thread panicking now causes Rojo to abort instead of existing as a zombie.
+    * Errors now have a list of causes, helping make many errors more clear.
 
 ## [0.6.0 Alpha 2](https://github.com/rojo-rbx/rojo/releases/tag/v0.6.0-alpha.2) (March 6, 2020)
 * Fixed `rojo upload` command always uploading models.

Cargo.lock

@@ -1665,6 +1665,7 @@ dependencies = [
 name = "rojo"
 version = "0.6.0-alpha.2"
 dependencies = [
+ "backtrace 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)",
  "criterion 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "crossbeam-channel 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "csv 1.1.3 (registry+https://github.com/rust-lang/crates.io-index)",

Cargo.toml

@@ -15,6 +15,12 @@ exclude = [
     "/test-projects/**",
 ]
 
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+
 [features]
 default = []
 
@@ -56,6 +62,7 @@ harness = false
 
 [dependencies]
 memofs = { version = "0.1.0", path = "memofs" }
+backtrace = "0.3"
 
 crossbeam-channel = "0.4.0"
 csv = "1.1.1"

src/bin.rs

@@ -1,49 +1,10 @@
-use std::{error::Error, panic, process};
+use std::{env, error::Error, panic, process};
 
-use log::error;
+use backtrace::Backtrace;
 use structopt::StructOpt;
 
 use librojo::cli::{self, Options, Subcommand};
 
-fn main() {
-    let options = Options::from_args();
-
-    {
-        let log_filter = match options.verbosity {
-            0 => "warn",
-            1 => "warn,librojo=info",
-            2 => "warn,librojo=trace",
-            _ => "trace",
-        };
-
-        let log_env = env_logger::Env::default().default_filter_or(log_filter);
-
-        env_logger::Builder::from_env(log_env)
-            .format_timestamp(None)
-            .init();
-    }
-
-    let panic_result = panic::catch_unwind(|| {
-        if let Err(err) = run(options.subcommand) {
-            log::error!("{}", err);
-            process::exit(1);
-        }
-    });
-
-    if let Err(error) = panic_result {
-        let message = match error.downcast_ref::<&str>() {
-            Some(message) => message.to_string(),
-            None => match error.downcast_ref::<String>() {
-                Some(message) => message.clone(),
-                None => "<no message>".to_string(),
-            },
-        };
-
-        show_crash_message(&message);
-        process::exit(1);
-    }
-}
-
 fn run(subcommand: Subcommand) -> Result<(), Box<dyn Error>> {
     match subcommand {
         Subcommand::Init(init_options) => cli::init(init_options)?,
@@ -55,11 +16,74 @@ fn run(subcommand: Subcommand) -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
-fn show_crash_message(message: &str) {
+fn main() {
-    error!("Rojo crashed!");
+    panic::set_hook(Box::new(|panic_info| {
-    error!("This is a bug in Rojo.");
+        // PanicInfo's payload is usually a &'static str or String.
-    error!("");
+        // See: https://doc.rust-lang.org/beta/std/panic/struct.PanicInfo.html#method.payload
-    error!("Please consider filing a bug: https://github.com/rojo-rbx/rojo/issues");
+        let message = match panic_info.payload().downcast_ref::<&str>() {
-    error!("");
+            Some(message) => message.to_string(),
-    error!("Details: {}", message);
+            None => match panic_info.payload().downcast_ref::<String>() {
+                Some(message) => message.clone(),
+                None => "<no message>".to_string(),
+            },
+        };
+
+        log::error!("Rojo crashed!");
+        log::error!("This is probably a Rojo bug.");
+        log::error!("");
+        log::error!("Please consider filing an issue: https://github.com/rojo-rbx/rojo/issues");
+        log::error!("");
+        log::error!("Details: {}", message);
+
+        if let Some(location) = panic_info.location() {
+            log::error!("in file {} on line {}", location.file(), location.line());
+        }
+
+        // When using the backtrace crate, we need to check the RUST_BACKTRACE
+        // environment variable ourselves. Once we switch to the (currently
+        // unstable) std::backtrace module, we won't need to do this anymore.
+        let should_backtrace = env::var("RUST_BACKTRACE")
+            .map(|var| var == "1")
+            .unwrap_or(false);
+
+        if should_backtrace {
+            eprintln!("{:?}", Backtrace::new());
+        } else {
+            eprintln!(
+                "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace."
+            );
+        }
+
+        process::exit(1);
+    }));
+
+    let options = Options::from_args();
+
+    let log_filter = match options.verbosity {
+        0 => "warn",
+        1 => "warn,librojo=info",
+        2 => "warn,librojo=trace",
+        _ => "trace",
+    };
+
+    let log_env = env_logger::Env::default().default_filter_or(log_filter);
+
+    env_logger::Builder::from_env(log_env)
+        .format_module_path(false)
+        .format_timestamp(None)
+        // Indent following lines equal to the log level label, like `[ERROR] `
+        .format_indent(Some(8))
+        .init();
+
+    if let Err(err) = run(options.subcommand) {
+        log::error!("{}", err);
+
+        let mut current_err: &dyn Error = &*err;
+        while let Some(source) = current_err.source() {
+            log::error!("  caused by {}", err);
+            current_err = &*source;
+        }
+
+        process::exit(1);
+    }
 }