Add rerun --strict: crash if any warning or error is logged (#1812)

* Add `rerun --strict`: crash if any warning or error is logged

Part of #1483

* Can't doc-test private functions

crates/re_log/src/lib.rs

@@ -35,6 +35,11 @@ pub use {
     setup::*,
 };
 
+/// Re-exports of other crates.
+pub mod external {
+    pub use log;
+}
+
 /// Never log anything less serious than a `WARN` from these crates.
 const CRATES_AT_WARN_LEVEL: [&str; 3] = [
     // wgpu crates spam a lot on info level, which is really annoying

crates/rerun/src/crash_handler.rs

@@ -23,7 +23,7 @@ fn install_panic_hook(_build_info: BuildInfo) {
     let previous_panic_hook = std::panic::take_hook();
 
     std::panic::set_hook(Box::new(move |panic_info: &std::panic::PanicInfo<'_>| {
-        let callstack = callstack_from("panicking::panic_fmt\n");
+        let callstack = callstack_from(&["panicking::panic_fmt\n"]);
 
         let file_line = panic_info.location().map(|location| {
             let file = anonymize_source_file_path(&std::path::PathBuf::from(location.file()));
@@ -215,21 +215,38 @@ fn install_signal_handler(build_info: BuildInfo) {
     }
 
     fn callstack() -> String {
-        callstack_from("install_signal_handler::signal_handler\n")
+        callstack_from(&["install_signal_handler::signal_handler\n"])
     }
 }
 
-fn callstack_from(start_pattern: &str) -> String {
+/// Get a nicely formatted callstack.
+///
+/// You can give this function a list of substrings to look for, e.g. names of functions.
+/// If any of these substrings matches, anything before that is removed from the callstack.
+/// For example:
+///
+/// ```ignore
+/// fn print_callstack() {
+///     eprintln!("{}", callstack_from(&["print_callstack"]));
+/// }
+/// ```
+pub fn callstack_from(start_patterns: &[&str]) -> String {
     let backtrace = backtrace::Backtrace::new();
     let stack = backtrace_to_string(&backtrace);
 
     // Trim it a bit:
     let mut stack = stack.as_str();
 
+    let start_patterns = start_patterns
+        .iter()
+        .chain(std::iter::once(&"callstack_from"));
+
     // Trim the top (closest to the panic handler) to cut out some noise:
-    if let Some(offset) = stack.find(start_pattern) {
-        let prev_newline = stack[..offset].rfind('\n').map_or(0, |newline| newline + 1);
-        stack = &stack[prev_newline..];
+    for start_pattern in start_patterns {
+        if let Some(offset) = stack.find(start_pattern) {
+            let prev_newline = stack[..offset].rfind('\n').map_or(0, |newline| newline + 1);
+            stack = &stack[prev_newline..];
+        }
     }
 
     // Trim the bottom to cut out code that sets up the callstack:

crates/rerun/src/run.rs

@@ -64,6 +64,10 @@ struct Args {
     #[clap(long)]
     profile: bool,
 
+    /// Exit with a non-zero exit code if any warning or error is logged. Useful for tests.
+    #[clap(long)]
+    strict: bool,
+
     /// An upper limit on how much memory the Rerun Viewer should use.
     ///
     /// When this limit is used, Rerun will purge the oldest data.
@@ -187,6 +191,11 @@ where
         return Ok(0);
     }
 
+    if args.strict {
+        re_log::add_boxed_logger(Box::new(StrictLogger {})).expect("Failed to enter --strict mode");
+        re_log::info!("--strict mode: any warning or error will cause Rerun to panic.");
+    }
+
     let res = if let Some(commands) = &args.commands {
         match commands {
             #[cfg(all(feature = "analytics"))]
@@ -539,3 +548,35 @@ pub fn setup_ctrl_c_handler() -> (tokio::sync::broadcast::Receiver<()>, Arc<Atom
     .expect("Error setting Ctrl-C handler");
     (receiver, shutdown_return)
 }
+
+// ----------------------------------------------------------------------------
+
+use re_log::external::log;
+
+struct StrictLogger {}
+
+impl log::Log for StrictLogger {
+    fn enabled(&self, metadata: &log::Metadata<'_>) -> bool {
+        match metadata.level() {
+            log::Level::Error | log::Level::Warn => true,
+            log::Level::Info | log::Level::Debug | log::Level::Trace => false,
+        }
+    }
+
+    fn log(&self, record: &log::Record<'_>) {
+        let level = match record.level() {
+            log::Level::Error => "error",
+            log::Level::Warn => "warning",
+            log::Level::Info | log::Level::Debug | log::Level::Trace => return,
+        };
+
+        eprintln!("{level} logged in --strict mode: {}", record.args());
+        eprintln!(
+            "{}",
+            crate::crash_handler::callstack_from(&["log::__private_api_log"])
+        );
+        std::process::exit(1);
+    }
+
+    fn flush(&self) {}
+}