tests: put mocking functionality into a crate (#2009)

... instead of `#[path = ""]` importing it everywhere.

Make sure to use a diff review tool that understands file renaming 😅
(GitHub's diff view does.)

## Motivation

Transparency: I want to use the mocking functionality in the development
of a tracing component out-of-tree.

Additionally, this reduces the use of `#[path] mod` and file
multiple-inclusion, which aren't that great of a practice.

## Solution

The tracing test support module was already well self-contained, due to
being `#[path] mod` used in multiple places. As such, extracting it to
its own crate is rather mechanical, with no surprising blockers.

We additionally move the tracing-futures support module contents into
tracing_mock, for convenience. The one function which relies on
tokio-test is made optional.

It's a reasonable result for this functionality to stay unpublished, and
only used inside the repo, but pulling it out into a directly reusable
chunk instead of abusing the module system to reuse it via
multiple-inclusion is an improvement to code structure and
modularization.

Author: CAD97

Cargo.toml

@@ -10,6 +10,7 @@ members = [
     "tracing-tower",
     "tracing-log",
     "tracing-macros",
+    "tracing-mock",
     "tracing-opentelemetry",
     "tracing-subscriber",
     "tracing-serde",

tracing-attributes/Cargo.toml

@@ -40,6 +40,7 @@ quote = "1"
 
 [dev-dependencies]
 tracing = { path = "../tracing", version = "0.2" }
+tracing-mock = { path = "../tracing-mock", features = ["tokio-test"] }
 tokio-test = { version = "0.2.0" }
 tracing-core = { path = "../tracing-core", version = "0.2"}
 async-trait = "0.1.44"

tracing-attributes/tests/async_fn.rs

@@ -1,8 +1,4 @@
-#[path = "../../tracing-futures/tests/support.rs"]
-// we don't use some of the test support functions, but `tracing-futures` does.
-#[allow(dead_code)]
-mod support;
-use support::*;
+use tracing_mock::*;
 
 use std::{future::Future, pin::Pin, sync::Arc};
 use tracing::collect::with_default;

tracing-attributes/tests/destructuring.rs

@@ -1,8 +1,6 @@
-mod support;
-use support::*;
-
 use tracing::collect::with_default;
 use tracing_attributes::instrument;
+use tracing_mock::*;
 
 #[test]
 fn destructure_tuples() {

tracing-attributes/tests/err.rs

@@ -1,12 +1,7 @@
-#[path = "../../tracing-futures/tests/support.rs"]
-// we don't use some of the test support functions, but `tracing-futures` does.
-#[allow(dead_code)]
-mod support;
-use support::*;
-
 use tracing::collect::with_default;
 use tracing::Level;
 use tracing_attributes::instrument;
+use tracing_mock::*;
 
 use std::convert::TryFrom;
 use std::num::TryFromIntError;

tracing-attributes/tests/fields.rs

@@ -1,10 +1,8 @@
-mod support;
-use support::*;
-
-use crate::support::field::mock;
-use crate::support::span::NewSpan;
 use tracing::collect::with_default;
 use tracing_attributes::instrument;
+use tracing_mock::field::mock;
+use tracing_mock::span::NewSpan;
+use tracing_mock::*;
 
 #[instrument(fields(foo = "bar", dsa = true, num = 1))]
 fn fn_no_param() {}

tracing-attributes/tests/instrument.rs

@@ -1,9 +1,7 @@
-mod support;
-use support::*;
-
 use tracing::collect::with_default;
 use tracing::Level;
 use tracing_attributes::instrument;
+use tracing_mock::*;
 
 #[test]
 fn override_everything() {

tracing-attributes/tests/levels.rs

@@ -1,9 +1,7 @@
-mod support;
-use support::*;
-
 use tracing::collect::with_default;
 use tracing::Level;
 use tracing_attributes::instrument;
+use tracing_mock::*;
 
 #[test]
 fn named_levels() {

tracing-attributes/tests/names.rs

@@ -1,8 +1,6 @@
-mod support;
-use support::*;
-
 use tracing::collect::with_default;
 use tracing_attributes::instrument;
+use tracing_mock::*;
 
 #[instrument]
 fn default_name() {}

tracing-attributes/tests/ret.rs

@@ -1,11 +1,6 @@
-#[path = "../../tracing-futures/tests/support.rs"]
-// we don't use some of the test support functions, but `tracing-futures` does.
-#[allow(dead_code)]
-mod support;
-use support::*;
-
 use std::convert::TryFrom;
 use std::num::TryFromIntError;
+use tracing_mock::*;
 
 use tracing::{collect::with_default, Level};
 use tracing_attributes::instrument;