wip(windows): make sure app panics show up in the logs (#3085)

Related to this discussion
https://github.com/firezone/firezone/pull/2990#discussion_r1439629571

Add a dependency on the `tracing-panic` crate. This is about 100 lines
of code that adds a panic handle so app panics get a line number, file
name, etc. in the logs. No backtrace I think since we stripe symbols for
release builds. I _think_ the line numbers are baked into the panic
macro so those might still stay.

@conectado I should remove the debug command before closing it, right?

rust/Cargo.lock

@@ -2068,6 +2068,7 @@ dependencies = [
  "tokio",
  "tracing",
  "tracing-log 0.2.0",
+ "tracing-panic",
  "tracing-subscriber",
  "url",
  "uuid",
@@ -6619,6 +6620,16 @@ dependencies = [
  "tracing-subscriber",
 ]
 
+[[package]]
+name = "tracing-panic"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eaf80030ce049691c9922d75be63cadf345110a245cd4581833c66f87c02ad25"
+dependencies = [
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "tracing-serde"
 version = "0.1.3"

rust/windows-client/src-tauri/Cargo.toml

@@ -34,6 +34,7 @@ tracing-log = "0.2"
 tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }
 url = { version = "2.5.0", features = ["serde"] }
 uuid = { version = "1.5.0", features = ["v4"] }
+tracing-panic = "0.1.1"
 zip = { version = "0.6.6", features = ["deflate", "time"], default-features = false }
 
 # These dependencies are locked behind `cfg(windows)` because they either can't compile at all on Linux, or they need native dependencies like glib that are difficult to get. Try not to add more here.

rust/windows-client/src-tauri/src/client.rs

@@ -32,6 +32,7 @@ pub(crate) struct AppLocalDataDir(std::path::PathBuf);
 const CREATE_NO_WINDOW: u32 = 0x08000000;
 
 pub(crate) fn run() -> Result<()> {
+    std::panic::set_hook(Box::new(tracing_panic::panic_hook));
     let cli = cli::Cli::parse();
 
     match cli.command {
@@ -66,6 +67,7 @@ pub(crate) fn run() -> Result<()> {
             println!("debug");
             Ok(())
         }
+        Some(Cmd::DebugCrash) => debug_commands::crash(),
         Some(Cmd::DebugHostname) => debug_commands::hostname(),
         Some(Cmd::DebugPipeServer) => debug_commands::pipe_server(),
         Some(Cmd::DebugWintun) => debug_commands::wintun(cli),

rust/windows-client/src-tauri/src/client/cli.rs

@@ -12,6 +12,7 @@ pub struct Cli {
 #[derive(clap::Subcommand)]
 pub enum CliCommands {
     Debug,
+    DebugCrash,
     DebugHostname,
     DebugPipeServer,
     DebugWintun,

rust/windows-client/src-tauri/src/client/debug_commands.rs

@@ -8,6 +8,14 @@ use tokio::runtime::Runtime;
 // TODO: In tauri-plugin-deep-link, this is the identifier in tauri.conf.json
 const PIPE_NAME: &str = "dev.firezone.client";
 
+pub fn crash() -> Result<()> {
+    // `_` doesn't seem to work here, the log files end up empty
+    let _handles = crate::client::logging::setup("debug")?;
+    tracing::info!("started log (DebugCrash)");
+
+    panic!("purposely crashing to see if it shows up in logs");
+}
+
 pub fn hostname() -> Result<()> {
     println!(
         "{:?}",

rust/windows-client/src-tauri/src/client/logging.rs

@@ -16,6 +16,9 @@ use tracing::subscriber::set_global_default;
 use tracing_log::LogTracer;
 use tracing_subscriber::{fmt, layer::SubscriberExt, reload, EnvFilter, Layer, Registry};
 
+/// If you don't store `Handles` in a variable, the file logger handle will drop immediately,
+/// resulting in empty log files.
+#[must_use]
 pub(crate) struct Handles {
     pub logger: file_logger::Handle,
     pub _reloader: reload::Handle<EnvFilter, Registry>,