Rollup merge of #143180 - jieyouxu:forest, r=Kobzol

Use `tracing-forest` instead of `tracing-tree` for bootstrap tracing

I find the `tracing-forest` output easier to comprehend.

Note that this is not a strict improvement -- `tracing-forest` output contains some emojis and redundant log levels, but customizing it seems to be... non-trivial. Despite this, I still find `tracing-forest` easier to follow than `tracing-tree`, even when I tried to tune `tracing-tree` output.

### Preview

```bash
BOOTSTRAP_TRACING=debug ./x test library/std --dry-run
```

With `tracing-forest` (this PR), it looks like

![Screenshot 2025-06-29 174802](https://github.com/user-attachments/assets/1ab9150f-48f8-4fb3-b004-27bcf8bbc0f5)

With `tracing-tree` (before this PR), it looked like

![Screenshot 2025-06-29 175227](https://github.com/user-attachments/assets/659e254d-15ab-47dd-af11-98e2331d4d7a)

r? `@Kobzol`

Author: matthiaskrgr

src/bootstrap/Cargo.lock

@@ -11,6 +11,15 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "ansi_term"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d52a9bb7ec0cf484c551830a7ce27bd20d67eac647e1befb56b0be4ee39a55d2"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "anstyle"
 version = "1.0.10"
@@ -62,8 +71,8 @@ dependencies = [
  "toml",
  "tracing",
  "tracing-chrome",
+ "tracing-forest",
  "tracing-subscriber",
- "tracing-tree",
  "walkdir",
  "windows",
  "xz2",
@@ -449,15 +458,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "nu-ansi-term"
-version = "0.50.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d4a28e057d01f97e61255210fcff094d74ed0466038633e95017f5beb68e4399"
-dependencies = [
- "windows-sys 0.52.0",
-]
-
 [[package]]
 name = "objc2-core-foundation"
 version = "0.3.1"
@@ -775,6 +775,26 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6aaf5339b578ea85b50e080feb250a3e8ae8cfcdff9a461c9ec2904bc923f52"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "thread_local"
 version = "1.1.8"
@@ -837,6 +857,19 @@ dependencies = [
  "valuable",
 ]
 
+[[package]]
+name = "tracing-forest"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee40835db14ddd1e3ba414292272eddde9dad04d3d4b65509656414d1c42592f"
+dependencies = [
+ "ansi_term",
+ "smallvec",
+ "thiserror",
+ "tracing",
+ "tracing-subscriber",
+]
+
 [[package]]
 name = "tracing-log"
 version = "0.2.0"
@@ -855,7 +888,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e8189decb5ac0fa7bc8b96b7cb9b2701d60d48805aca84a238004d665fcc4008"
 dependencies = [
  "matchers",
- "nu-ansi-term 0.46.0",
+ "nu-ansi-term",
  "once_cell",
  "regex",
  "sharded-slab",
@@ -866,18 +899,6 @@ dependencies = [
  "tracing-log",
 ]
 
-[[package]]
-name = "tracing-tree"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f459ca79f1b0d5f71c54ddfde6debfc59c8b6eeb46808ae492077f739dc7b49c"
-dependencies = [
- "nu-ansi-term 0.50.1",
- "tracing-core",
- "tracing-log",
- "tracing-subscriber",
-]
-
 [[package]]
 name = "typenum"
 version = "1.17.0"

src/bootstrap/Cargo.toml

@@ -7,7 +7,7 @@ default-run = "bootstrap"
 
 [features]
 build-metrics = ["sysinfo"]
-tracing = ["dep:tracing", "dep:tracing-chrome", "dep:tracing-subscriber", "dep:tracing-tree"]
+tracing = ["dep:tracing", "dep:tracing-chrome", "dep:tracing-subscriber", "dep:tracing-forest"]
 
 [lib]
 path = "src/lib.rs"
@@ -64,7 +64,7 @@ sysinfo = { version = "0.35.0", default-features = false, optional = true, featu
 tracing = { version = "0.1", optional = true, features = ["attributes"] }
 tracing-chrome = { version = "0.7", optional = true }
 tracing-subscriber = { version = "0.3", optional = true, features = ["env-filter", "fmt", "registry", "std"] }
-tracing-tree = { version = "0.4.0", optional = true }
+tracing-forest = { version = "0.1.6", optional = true, default-features =  false, features = ["smallvec", "ansi", "env-filter"] }
 
 [target.'cfg(windows)'.dependencies.junction]
 version = "1.0.0"

src/bootstrap/src/bin/main.rs

@@ -217,12 +217,11 @@ fn check_version(config: &Config) -> Option<String> {
 //   "tracing", instrument(..))]`.
 #[cfg(feature = "tracing")]
 fn setup_tracing() -> impl Drop {
+    use tracing_forest::ForestLayer;
     use tracing_subscriber::EnvFilter;
     use tracing_subscriber::layer::SubscriberExt;
 
     let filter = EnvFilter::from_env("BOOTSTRAP_TRACING");
-    // cf. <https://docs.rs/tracing-tree/latest/tracing_tree/struct.HierarchicalLayer.html>.
-    let layer = tracing_tree::HierarchicalLayer::default().with_targets(true).with_indent_amount(2);
 
     let mut chrome_layer = tracing_chrome::ChromeLayerBuilder::new().include_args(true);
 
@@ -233,7 +232,8 @@ fn setup_tracing() -> impl Drop {
 
     let (chrome_layer, _guard) = chrome_layer.build();
 
-    let registry = tracing_subscriber::registry().with(filter).with(layer).with(chrome_layer);
+    let registry =
+        tracing_subscriber::registry().with(filter).with(ForestLayer::default()).with(chrome_layer);
 
     tracing::subscriber::set_global_default(registry).unwrap();
     _guard