feat: add support for writing tracing debug info to file (#3790)

# Description

## Problem\*

Turning rtacing on/off by adding code each time is cumbersome.

## Summary\*

Allows to turn tracing on by defining `env` `NARGO_LOG_DIR` =
`/path/to/directory/with/logs/`

Our own tracing would be aded gradually on as needed basis. By enabling
this we still benefit from other crates using tracing.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: Tom French <[email protected]>

Cargo.toml

@@ -122,6 +122,8 @@ num-traits = "0.2"
 similar-asserts = "1.5.0"
 log = "0.4.17"
 
+tracing = "0.1.40"
+
 [profile.dev]
 # This is required to be able to run `cargo test` in acvm_js due to the `locals exceeds maximum` error.
 # See https://ritik-mishra.medium.com/resolving-the-wasm-pack-error-locals-exceed-maximum-ec3a9d96685b

cspell.json

@@ -5,6 +5,7 @@
         "acir",
         "acvm",
         "aeiou",
+        "appender",
         "arithmetization",
         "arity",
         "arkworks",

tooling/nargo_cli/Cargo.toml

@@ -53,6 +53,11 @@ tokio = { version = "1.0", features = ["io-std"] }
 backend-interface = { path = "../backend_interface" }
 bb_abstraction_leaks.workspace = true
 
+# Logs
+tracing.workspace = true
+tracing-subscriber = "0.3.18"
+tracing-appender = "0.2.3"
+
 [target.'cfg(not(unix))'.dependencies]
 tokio-util = { version = "0.7.8", features = ["compat"] }
 

tooling/nargo_cli/src/main.rs

@@ -11,15 +11,28 @@ mod backends;
 mod cli;
 mod errors;
 
+use std::env;
+
 use color_eyre::config::HookBuilder;
 use env_logger::{Builder, Env};
+use tracing_appender::rolling;
 
 const PANIC_MESSAGE: &str = "This is a bug. We may have already fixed this in newer versions of Nargo so try searching for similar issues at https://github.com/noir-lang/noir/issues/.\nIf there isn't an open issue for this bug, consider opening one at https://github.com/noir-lang/noir/issues/new?labels=bug&template=bug_report.yml";
 
 fn main() {
     let env = Env::default().filter_or("NOIR_LOG", "error"); // Default to 'error' if NOIR_LOG is not set
     Builder::from_env(env).init();
 
+    // Setup tracing
+    if let Ok(log_dir) = env::var("NARGO_LOG_DIR") {
+        let debug_file = rolling::daily(log_dir, "nargo-log");
+        tracing_subscriber::fmt()
+            .with_writer(debug_file)
+            .with_ansi(false)
+            .with_max_level(tracing::Level::TRACE)
+            .init();
+    }
+
     // Register a panic hook to display more readable panic messages to end-users
     let (panic_hook, _) =
         HookBuilder::default().display_env_section(false).panic_section(PANIC_MESSAGE).into_hooks();