Could we form a offcial pattern to emit logs with some contexts

[hyf0]

Roughly, to do debugging I wrote something like

#[derive(Debug, Default, Clone)]
pub struct ContextedTracer {
  context: Vec<String>,
}

impl ContextedTracer {
  pub fn context(mut self, ctxt: String) -> Self {
    self.context.push(ctxt);
    self
  }

  pub fn emit_trace(&self, info: String) {
    for ctxt in &self.context {
      tracing::trace!("{}: {}", ansi_term::Color::Yellow.paint("context"), ctxt);
    }
    tracing::trace!(info)
  }
}

The could is rough. But I managed to use it to find bugs.

More important, I think the dx in the following code is much better.

// init the tracer with some contexts
let tr =  ContextedTracer::default()
  .context("xxx")
  .context("xxx");

// nested
for item in items {
  let tr = tr.clone().context(item.id);

  tr.emit_trace("something happen")
  for key in item.content {
      tr.clone().context(key).emit_trace("something about the key")
  }
}

I post this pattern here to see if the community already has the pattern.