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It's a reasonable result for this functionality to stay unpublished, and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.

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;

tracing-attributes/tests/targets.rs

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

tracing-futures/Cargo.toml

@@ -38,6 +38,7 @@ tokio = { version = "0.1", optional = true }
 tokio = "0.1.22"
 tokio-test = "0.2"
 tracing-core = { path = "../tracing-core", version = "0.2" }
+tracing-mock = { path = "../tracing-mock" }
 
 [badges]
 maintenance = { status = "actively-developed" }

tracing-futures/src/lib.rs

@@ -512,17 +512,10 @@ impl<T> WithDispatch<T> {
     }
 }
 
-#[cfg(test)]
-pub(crate) use self::support as test_support;
-// This has to have the same name as the module in `tracing`.
-#[path = "../../tracing/tests/support/mod.rs"]
-#[cfg(test)]
-#[allow(unreachable_pub)]
-pub(crate) mod support;
-
 #[cfg(test)]
 mod tests {
-    use super::{test_support::*, *};
+    use super::*;
+    use tracing_mock::*;
 
     #[cfg(feature = "futures-01")]
     mod futures_01_tests {

tracing-futures/tests/std_future.rs

@@ -1,8 +1,6 @@
-mod support;
-use support::*;
-
 use tracing::Instrument;
 use tracing::{collect::with_default, Level};
+use tracing_mock::*;
 
 #[test]
 fn enter_exit_is_reasonable() {

tracing-mock/Cargo.toml

@@ -0,0 +1,27 @@
+## BIG SCARY NOTE
+# This Cargo.toml does not match the repo conventions YET
+# Before releasing to crates.io: make it so!
+
+[package]
+name = "tracing-mock"
+version = "0.2.0"
+authors = [
+    "Eliza Weisman <eliza@buoyant.io>",
+    "Tokio Contributors <team@tokio.rs>",
+]
+license = "MIT"
+readme = "README.md"
+repository = "https://github.com/tokio-rs/tracing"
+homepage = "https://tokio.rs"
+edition = "2018"
+rust-version = "1.49.0"
+publish = false
+
+[dependencies]
+tracing = { path = "../tracing", version = "0.2", default-features = false }
+tracing-core = { path = "../tracing-core", version = "0.2", default-features = false }
+tokio-test = { version = "0.2.0", optional = true }
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]

tracing-mock/LICENSE

@@ -0,0 +1,25 @@
+Copyright (c) 2019 Tokio Contributors
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

tracing/tests/support/event.rs → tracing-mock/src/event.rs

@@ -10,7 +10,7 @@ use std::fmt;
 #[derive(Debug, Default, Eq, PartialEq)]
 pub struct MockEvent {
     pub fields: Option<field::Expect>,
-    pub(in crate::support) parent: Option<Parent>,
+    pub(crate) parent: Option<Parent>,
     metadata: metadata::Expect,
 }
 
@@ -78,7 +78,7 @@ impl MockEvent {
         }
     }
 
-    pub(in crate::support) fn check(&mut self, event: &tracing::Event<'_>) {
+    pub(crate) fn check(&mut self, event: &tracing::Event<'_>) {
         let meta = event.metadata();
         let name = meta.name();
         self.metadata

tracing-futures/tests/support.rs → tracing-mock/src/lib.rs

@@ -1,15 +1,21 @@
-// this is the only way to make the path attribute play nice with `in
-// crate::support`...
-#[allow(clippy::module_inception)]
-#[path = "../../tracing/tests/support/mod.rs"]
-mod support;
 use std::{
-    future::Future,
     pin::Pin,
     task::{Context, Poll},
 };
-pub use support::*;
-use tokio_test::task;
+
+pub mod collector;
+pub mod event;
+pub mod field;
+mod metadata;
+pub mod span;
+
+#[derive(Debug, Eq, PartialEq)]
+pub(crate) enum Parent {
+    ContextualRoot,
+    Contextual(String),
+    ExplicitRoot,
+    Explicit(String),
+}
 
 pub struct PollN<T, E> {
     and_return: Option<Result<T, E>>,
@@ -56,10 +62,13 @@ impl PollN<(), ()> {
     }
 }
 
+#[cfg(feature = "tokio-test")]
 pub fn block_on_future<F>(future: F) -> F::Output
 where
-    F: Future,
+    F: std::future::Future,
 {
+    use tokio_test::task;
+
     let mut task = task::spawn(future);
     loop {
         if let Poll::Ready(v) = task.poll() {

tracing/tests/support/metadata.rs → tracing-mock/src/metadata.rs

@@ -9,7 +9,7 @@ pub struct Expect {
 }
 
 impl Expect {
-    pub(in crate::support) fn check(&self, actual: &Metadata<'_>, ctx: fmt::Arguments<'_>) {
+    pub(crate) fn check(&self, actual: &Metadata<'_>, ctx: fmt::Arguments<'_>) {
         if let Some(ref expected_name) = self.name {
             let name = actual.name();
             assert!(

tracing/tests/support/span.rs → tracing-mock/src/span.rs

@@ -8,14 +8,14 @@ use std::fmt;
 /// `subscriber` module.
 #[derive(Clone, Debug, Default, Eq, PartialEq)]
 pub struct MockSpan {
-    pub(in crate::support) metadata: metadata::Expect,
+    pub(crate) metadata: metadata::Expect,
 }
 
 #[derive(Debug, Default, Eq, PartialEq)]
 pub struct NewSpan {
-    pub(in crate::support) span: MockSpan,
-    pub(in crate::support) fields: field::Expect,
-    pub(in crate::support) parent: Option<Parent>,
+    pub(crate) span: MockSpan,
+    pub(crate) fields: field::Expect,
+    pub(crate) parent: Option<Parent>,
 }
 
 pub fn mock() -> MockSpan {
@@ -96,11 +96,6 @@ impl MockSpan {
             ..Default::default()
         }
     }
-
-    pub(in crate::support) fn check_metadata(&self, actual: &tracing::Metadata<'_>) {
-        self.metadata.check(actual, format_args!("span {}", self));
-        assert!(actual.is_span(), "expected a span but got {:?}", actual);
-    }
 }
 
 impl fmt::Display for MockSpan {

tracing-subscriber/Cargo.toml

@@ -65,6 +65,7 @@ thread_local = { version = "1.1.4", optional = true }
 
 [dev-dependencies]
 tracing = { path = "../tracing", version = "0.2" }
+tracing-mock = { path = "../tracing-mock" }
 log = "0.4"
 tracing-log = { path = "../tracing-log", version = "0.2" }
 criterion = { version = "0.3", default_features = false }

tracing-subscriber/tests/duplicate_spans.rs

@@ -1,5 +1,4 @@
 #![cfg(all(feature = "env-filter", feature = "fmt"))]
-mod support;
 use tracing::{self, collect::with_default, Span};
 use tracing_subscriber::{filter::EnvFilter, fmt::Collector};
 

tracing-subscriber/tests/field_filter.rs

@@ -1,7 +1,7 @@
 #![cfg(feature = "env-filter")]
-mod support;
-use self::support::*;
+
 use tracing::{self, collect::with_default, Level};
+use tracing_mock::*;
 use tracing_subscriber::{filter::EnvFilter, prelude::*};
 
 #[test]

tracing-subscriber/tests/filter.rs

@@ -1,8 +1,7 @@
 #![cfg(feature = "env-filter")]
 
-mod support;
-use self::support::*;
 use tracing::{self, collect::with_default, Level};
+use tracing_mock::*;
 use tracing_subscriber::{
     filter::{EnvFilter, LevelFilter},
     prelude::*,

tracing-subscriber/tests/filter_log.rs

@@ -1,7 +1,7 @@
 #![cfg(all(feature = "env-filter", feature = "tracing-log"))]
-mod support;
-use self::support::*;
+
 use tracing::{self, Level};
+use tracing_mock::*;
 use tracing_subscriber::{filter::EnvFilter, prelude::*};
 
 mod my_module {

tracing-subscriber/tests/reload_max_log_level.rs

@@ -1,8 +1,7 @@
 #![cfg(all(feature = "env-filter", feature = "tracing-log"))]
 
-mod support;
-use self::support::*;
 use tracing::{self, Level};
+use tracing_mock::*;
 use tracing_subscriber::{filter::LevelFilter, prelude::*, reload};
 
 #[test]

tracing-subscriber/tests/same_len_filters.rs

@@ -1,9 +1,9 @@
 // These tests include field filters with no targets, so they have to go in a
 // separate file.
 #![cfg(feature = "env-filter")]
-mod support;
-use self::support::*;
+
 use tracing::{self, collect::with_default, Level};
+use tracing_mock::*;
 use tracing_subscriber::{filter::EnvFilter, prelude::*};
 
 #[test]