rustc_log: expose tracing-tree "wraparound" in an env var

Author: RalfJung

compiler/rustc_log/src/lib.rs

@@ -57,6 +57,7 @@ pub struct LoggerConfig {
  pub verbose_entry_exit: Result<String, VarError>,
  pub verbose_thread_ids: Result<String, VarError>,
  pub backtrace: Result<String, VarError>,
+ pub wraptree: Result<String, VarError>,
 }
 
 impl LoggerConfig {
@@ -67,6 +68,7 @@ impl LoggerConfig {
  verbose_entry_exit: env::var(format!("{env}_ENTRY_EXIT")),
  verbose_thread_ids: env::var(format!("{env}_THREAD_IDS")),
  backtrace: env::var(format!("{env}_BACKTRACE")),
+ wraptree: env::var(format!("{env}_WRAPTREE")),
  }
  }
 }
@@ -99,7 +101,7 @@ pub fn init_logger(cfg: LoggerConfig) -> Result<(), Error> {
  Err(_) => false,
  };
 
- let layer = tracing_tree::HierarchicalLayer::default()
+ let mut layer = tracing_tree::HierarchicalLayer::default()
  .with_writer(io::stderr)
  .with_indent_lines(true)
  .with_ansi(color_logs)
@@ -110,6 +112,16 @@ pub fn init_logger(cfg: LoggerConfig) -> Result<(), Error> {
  .with_thread_ids(verbose_thread_ids)
  .with_thread_names(verbose_thread_ids);
 
+ match cfg.wraptree {
+ Ok(v) => match v.parse::<usize>() {
+ Ok(v) => {
+ layer = layer.with_wraparound(v);
+ }
+ Err(_) => return Err(Error::InvalidWraptree(v)),
+ },
+ Err(_) => {} // no wraptree
+ }
+
  let subscriber = tracing_subscriber::Registry::default().with(filter).with(layer);
  match cfg.backtrace {
  Ok(str) => {
@@ -164,6 +176,7 @@ pub fn stderr_isatty() -> bool {
 pub enum Error {
  InvalidColorValue(String),
  NonUnicodeColorValue,
+ InvalidWraptree(String),
 }
 
 impl std::error::Error for Error {}
@@ -179,6 +192,10 @@ impl Display for Error {
  formatter,
  "non-Unicode log color value: expected one of always, never, or auto",
  ),
+ Error::InvalidWraptree(value) => write!(
+ formatter,
+ "invalid log WRAPTREE value '{value}': expected a non-negative integer",
+ ),
  }
  }
 }