Unrolled build for rust-lang#124242

Rollup merge of rust-lang#124242 - workingjubilee:describe-bootstrap-files-better, r=Mark-Simulacrum

bootstrap: Describe build_steps modules

One of my preferred ways to understand source code is to start with its API. This implies the code is documented reasonably accurately, even if it is a private API. The description of one of these modules had not been updated since 2015 and so was both terse and confusing, so I rewrote it. Then I noticed many others went unremarked, so I offered some remarks.

src/bootstrap/src/core/build_steps/clean.rs

@@ -1,4 +1,4 @@
-//! Implementation of `make clean` in rustbuild.
+//! `./x.py clean`
 //!
 //! Responsible for cleaning out a build directory of all old and stale
 //! artifacts to prepare for a fresh build. Currently doesn't remove the

src/bootstrap/src/core/build_steps/run.rs

@@ -1,3 +1,8 @@
+//! Build-and-run steps for in-repo tools
+//!
+//! A bit of a hodge-podge as e.g. if a tool's a test fixture it should be in `build_steps::test`.
+//! If it can be reached from `./x.py run` it can go here.
+
 use std::path::PathBuf;
 use std::process::Command;
 

src/bootstrap/src/core/build_steps/setup.rs

@@ -1,3 +1,10 @@
+//! First time setup of a dev environment
+//!
+//! These are build-and-run steps for `./x.py setup`, which allows quickly setting up the directory
+//! for modifying, building, and running the compiler and library. Running arbitrary configuration
+//! allows setting up things that cannot be simply captured inside the config.toml, in addition to
+//! leading people away from manually editing most of the config.toml values.
+
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::t;
 use crate::utils::change_tracker::CONFIG_CHANGE_HISTORY;
@@ -25,6 +32,8 @@ pub enum Profile {
     None,
 }
 
+static PROFILE_DIR: &str = "src/bootstrap/defaults";
+
 /// A list of historical hashes of `src/etc/rust_analyzer_settings.json`.
 /// New entries should be appended whenever this is updated so we can detect
 /// outdated vs. user-modified settings files.
@@ -41,7 +50,7 @@ static RUST_ANALYZER_SETTINGS: &str = include_str!("../../../../etc/rust_analyze
 
 impl Profile {
     fn include_path(&self, src_path: &Path) -> PathBuf {
-        PathBuf::from(format!("{}/src/bootstrap/defaults/config.{}.toml", src_path.display(), self))
+        PathBuf::from(format!("{}/{PROFILE_DIR}/config.{}.toml", src_path.display(), self))
     }
 
     pub fn all() -> impl Iterator<Item = Self> {
@@ -220,7 +229,7 @@ fn setup_config_toml(path: &PathBuf, profile: Profile, config: &Config) {
 
     let latest_change_id = CONFIG_CHANGE_HISTORY.last().unwrap().change_id;
     let settings = format!(
-        "# Includes one of the default files in src/bootstrap/defaults\n\
+        "# Includes one of the default files in {PROFILE_DIR}\n\
     profile = \"{profile}\"\n\
     change-id = {latest_change_id}\n"
     );

src/bootstrap/src/core/build_steps/suggest.rs

@@ -1,3 +1,5 @@
+//! Attempt to magically identify good tests to run
+
 #![cfg_attr(feature = "build-metrics", allow(unused))]
 
 use clap::Parser;

src/bootstrap/src/core/build_steps/test.rs

@@ -1,7 +1,7 @@
-//! Implementation of the test-related targets of the build system.
+//! Build-and-run steps for `./x.py test` test fixtures
 //!
-//! This file implements the various regression test suites that we execute on
-//! our CI.
+//! `./x.py test` (aka [`Kind::Test`]) is currently allowed to reach build steps in other modules.
+//! However, this contains ~all test parts we expect people to be able to build and run locally.
 
 use std::env;
 use std::ffi::OsStr;

src/bootstrap/src/core/build_steps/toolstate.rs

@@ -1,3 +1,9 @@
+//! [Toolstate] checks to keep tools building
+//!
+//! Reachable via `./x.py test` but mostly relevant for CI, since it isn't run locally by default.
+//!
+//! [Toolstate]: https://forge.rust-lang.org/infra/toolstate.html
+
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::utils::helpers::t;
 use serde_derive::{Deserialize, Serialize};