observability: tracing gum, automatically cross ref traceID (#5079)

* add some gum

* bump expander

* gum

* fix all remaining issues

* last fixup

* Update node/gum/proc-macro/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* change

* netowrk

* fixins

* chore

* allow optional fmt str + args, prep for expr as kv field

* tracing -> gum rename fallout

* restrict further

* allow multiple levels of field accesses

* another round of docs and a slip of the pen

* update ADR

* fixup lock fiel

* use target: instead of target=

* minors

* fix

* chore

* Update node/gum/README.md

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

polkadot/node/gum/src/lib.rs

@@ -0,0 +1,35 @@
+// Copyright 2022 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+#![deny(unused_crate_dependencies)]
+#![deny(missing_docs)]
+#![deny(clippy::dbg_macro)]
+
+//! A wrapper around `tracing` macros, to provide semi automatic
+//! `traceID` annotation without codebase turnover.
+
+pub use tracing::{enabled, event, Level};
+
+#[doc(hidden)]
+pub use jaeger::hash_to_trace_identifier;
+
+#[doc(hidden)]
+pub use polkadot_primitives::v2::{CandidateHash, Hash};
+
+pub use gum_proc_macro::{debug, error, info, trace, warn};
+
+#[cfg(test)]
+mod tests;

polkadot/node/gum/src/tests.rs

@@ -0,0 +1,104 @@
+// Copyright 2022 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+use super::*;
+pub use polkadot_primitives::v2::{CandidateHash, Hash};
+
+#[derive(Default, Debug)]
+struct Y {
+	#[allow(dead_code)]
+	x: u8,
+}
+
+#[test]
+fn plain() {
+	error!("plain");
+}
+
+#[test]
+fn wo_alias() {
+	let a: i32 = 7;
+	error!(target: "foo",
+		"Something something {}, {:?}, or maybe {}",
+		a,
+		b = Y::default(),
+		c = a
+	);
+}
+
+#[test]
+fn wo_unnecessary() {
+	let a: i32 = 7;
+	warn!(target: "bar",
+		a = a,
+		b = ?Y::default(),
+		"fff {c}",
+		c = a,
+	);
+}
+
+#[test]
+fn w_candidate_hash_value_assignment() {
+	let a: i32 = 7;
+	info!(target: "bar",
+		a = a,
+		// ad-hoc value
+		candidate_hash = %CandidateHash(Hash::repeat_byte(0xF0)),
+		b = ?Y::default(),
+		c = ?a,
+		"xxx",
+	);
+}
+
+#[test]
+fn w_candidate_hash_from_scope() {
+	let a: i32 = 7;
+	let candidate_hash = CandidateHash(Hash::repeat_byte(0xF1));
+	debug!(target: "bar",
+		a = a,
+		?candidate_hash,
+		b = ?Y::default(),
+		c = ?a,
+		"xxx",
+	);
+}
+
+#[test]
+fn w_candidate_hash_aliased() {
+	let a: i32 = 7;
+	let c_hash = Hash::repeat_byte(0xFA);
+	trace!(target: "bar",
+		a = a,
+		candidate_hash = ?c_hash,
+		b = ?Y::default(),
+		c = a,
+		"xxx",
+	);
+}
+
+#[test]
+fn w_candidate_hash_aliased_unnecessary() {
+	let a: i32 = 7;
+	let candidate_hash = CandidateHash(Hash::repeat_byte(0xFA));
+	info!(
+		target: "bar",
+		a = a,
+		candidate_hash = ?candidate_hash,
+		b = ?Y::default(),
+		c = a,
+		"xxx",
+	);
+}