Update all submodules that rustbuild doesn't depend on lazily

This only updates the submodules the first time they're needed, instead
of unconditionally the first time you run x.py.

Ideally, this would move *all* submodules and not exclude some tools and
backtrace. Unfortunately, cargo requires all `Cargo.toml` files in the
whole workspace to be present to build any crate.

On my machine, this takes the time for an initial submodule clone (for
`x.py --help`) from 55.70 to 15.87 seconds.

This uses exactly the same logic as the LLVM update used, modulo some
minor cleanups:
- Use a local variable for `src.join(relative_path)`
- Remove unnecessary arrays for `book!` macro and make the macro simpler to use
- Add more comments

src/bootstrap/bootstrap.py

@@ -989,21 +989,30 @@ def update_submodules(self):
         slow_submodules = self.get_toml('fast-submodules') == "false"
         start_time = time()
         if slow_submodules:
-            print('Unconditionally updating all submodules')
+            print('Unconditionally updating submodules')
         else:
             print('Updating only changed submodules')
         default_encoding = sys.getdefaultencoding()
-        submodules = [s.split(' ', 1)[1] for s in subprocess.check_output(
-            ["git", "config", "--file",
-             os.path.join(self.rust_root, ".gitmodules"),
-             "--get-regexp", "path"]
-        ).decode(default_encoding).splitlines()]
+        # Only update submodules that are needed to build bootstrap.  These are needed because Cargo
+        # currently requires everything in a workspace to be "locally present" when starting a
+        # build, and will give a hard error if any Cargo.toml files are missing.
+        # FIXME: Is there a way to avoid cloning these eagerly? Bootstrap itself doesn't need to
+        #   share a workspace with any tools - maybe it could be excluded from the workspace?
+        #   That will still require cloning the submodules the second you check the standard
+        #   library, though...
+        # FIXME: Is there a way to avoid hard-coding the submodules required?
+        # WARNING: keep this in sync with the submodules hard-coded in bootstrap/lib.rs
+        submodules = [
+            "src/tools/rust-installer",
+            "src/tools/cargo",
+            "src/tools/rls",
+            "src/tools/miri",
+            "library/backtrace",
+            "library/stdarch"
+        ]
         filtered_submodules = []
         submodules_names = []
         for module in submodules:
-            # This is handled by native::Llvm in rustbuild, not here
-            if module.endswith("llvm-project"):
-                continue
             check = self.check_submodule(module, slow_submodules)
             filtered_submodules.append((module, check))
             submodules_names.append(module)

src/bootstrap/check.rs

@@ -7,7 +7,7 @@ use crate::config::TargetSelection;
 use crate::tool::{prepare_tool_cargo, SourceType};
 use crate::INTERNER;
 use crate::{Compiler, Mode, Subcommand};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub struct Std {
@@ -72,6 +72,8 @@ impl Step for Std {
     }
 
     fn run(self, builder: &Builder<'_>) {
+        builder.update_submodule(&Path::new("library").join("stdarch"));
+
         let target = self.target;
         let compiler = builder.compiler(builder.top_stage, builder.config.build);
 

src/bootstrap/compile.rs

@@ -79,6 +79,8 @@ impl Step for Std {
             return;
         }
 
+        builder.update_submodule(&Path::new("library").join("stdarch"));
+
         let mut target_deps = builder.ensure(StartupObjects { compiler, target });
 
         let compiler_to_use = builder.compiler_for(compiler.stage, compiler.host, target);

src/bootstrap/doc.rs

@@ -22,8 +22,17 @@ use crate::config::{Config, TargetSelection};
 use crate::tool::{self, prepare_tool_cargo, SourceType, Tool};
 use crate::util::symlink_dir;
 
+macro_rules! submodule_helper {
+    ($path:expr, submodule) => {
+        $path
+    };
+    ($path:expr, submodule = $submodule:literal) => {
+        $submodule
+    };
+}
+
 macro_rules! book {
-    ($($name:ident, $path:expr, $book_name:expr;)+) => {
+    ($($name:ident, $path:expr, $book_name:expr $(, submodule $(= $submodule:literal)? )? ;)+) => {
         $(
             #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
         pub struct $name {
@@ -46,6 +55,10 @@ macro_rules! book {
             }
 
             fn run(self, builder: &Builder<'_>) {
+                $(
+                    let path = Path::new(submodule_helper!( $path, submodule $( = $submodule )? ));
+                    builder.update_submodule(&path);
+                )?
                 builder.ensure(RustbookSrc {
                     target: self.target,
                     name: INTERNER.intern_str($book_name),
@@ -59,13 +72,16 @@ macro_rules! book {
 
 // NOTE: When adding a book here, make sure to ALSO build the book by
 // adding a build step in `src/bootstrap/builder.rs`!
+// NOTE: Make sure to add the corresponding submodule when adding a new book.
+// FIXME: Make checking for a submodule automatic somehow (maybe by having a list of all submodules
+// and checking against it?).
 book!(
-    CargoBook, "src/tools/cargo/src/doc", "cargo";
-    EditionGuide, "src/doc/edition-guide", "edition-guide";
-    EmbeddedBook, "src/doc/embedded-book", "embedded-book";
-    Nomicon, "src/doc/nomicon", "nomicon";
-    Reference, "src/doc/reference", "reference";
-    RustByExample, "src/doc/rust-by-example", "rust-by-example";
+    CargoBook, "src/tools/cargo/src/doc", "cargo", submodule = "src/tools/cargo";
+    EditionGuide, "src/doc/edition-guide", "edition-guide", submodule;
+    EmbeddedBook, "src/doc/embedded-book", "embedded-book", submodule;
+    Nomicon, "src/doc/nomicon", "nomicon", submodule;
+    Reference, "src/doc/reference", "reference", submodule;
+    RustByExample, "src/doc/rust-by-example", "rust-by-example", submodule;
     RustdocBook, "src/doc/rustdoc", "rustdoc";
 );
 
@@ -197,22 +213,25 @@ impl Step for TheBook {
     /// * Index page
     /// * Redirect pages
     fn run(self, builder: &Builder<'_>) {
+        let relative_path = Path::new("src").join("doc").join("book");
+        builder.update_submodule(&relative_path);
+
         let compiler = self.compiler;
         let target = self.target;
 
         // build book
         builder.ensure(RustbookSrc {
             target,
             name: INTERNER.intern_str("book"),
-            src: INTERNER.intern_path(builder.src.join("src/doc/book")),
+            src: INTERNER.intern_path(builder.src.join(&relative_path)),
         });
 
         // building older edition redirects
         for edition in &["first-edition", "second-edition", "2018-edition"] {
             builder.ensure(RustbookSrc {
                 target,
                 name: INTERNER.intern_string(format!("book/{}", edition)),
-                src: INTERNER.intern_path(builder.src.join("src/doc/book").join(edition)),
+                src: INTERNER.intern_path(builder.src.join(&relative_path).join(edition)),
             });
         }
 
@@ -221,7 +240,7 @@ impl Step for TheBook {
 
         // build the redirect pages
         builder.info(&format!("Documenting book redirect pages ({})", target));
-        for file in t!(fs::read_dir(builder.src.join("src/doc/book/redirects"))) {
+        for file in t!(fs::read_dir(builder.src.join(&relative_path).join("redirects"))) {
             let file = t!(file);
             let path = file.path();
             let path = path.to_str().unwrap();

src/bootstrap/lib.rs

@@ -477,17 +477,120 @@ impl Build {
         slice::from_ref(&self.build.triple)
     }
 
+    // modified from `check_submodule` and `update_submodule` in bootstrap.py
+    /// Given a path to the directory of a submodule, update it.
+    ///
+    /// `relative_path` should be relative to the root of the git repository, not an absolute path.
+    pub(crate) fn update_submodule(&self, relative_path: &Path) {
+        fn dir_is_empty(dir: &Path) -> bool {
+            t!(std::fs::read_dir(dir)).next().is_none()
+        }
+
+        if !self.config.submodules {
+            return;
+        }
+
+        let absolute_path = self.config.src.join(relative_path);
+
+        // NOTE: The check for the empty directory is here because when running x.py the first time,
+        // the submodule won't be checked out. Check it out now so we can build it.
+        if !channel::GitInfo::new(false, relative_path).is_git() && !dir_is_empty(&absolute_path) {
+            return;
+        }
+
+        // check_submodule
+        if self.config.fast_submodules {
+            let checked_out_hash = output(
+                Command::new("git").args(&["rev-parse", "HEAD"]).current_dir(&absolute_path),
+            );
+            // update_submodules
+            let recorded = output(
+                Command::new("git")
+                    .args(&["ls-tree", "HEAD"])
+                    .arg(relative_path)
+                    .current_dir(&self.config.src),
+            );
+            let actual_hash = recorded
+                .split_whitespace()
+                .nth(2)
+                .unwrap_or_else(|| panic!("unexpected output `{}`", recorded));
+
+            // update_submodule
+            if actual_hash == checked_out_hash.trim_end() {
+                // already checked out
+                return;
+            }
+        }
+
+        println!("Updating submodule {}", relative_path.display());
+        self.run(
+            Command::new("git")
+                .args(&["submodule", "-q", "sync"])
+                .arg(relative_path)
+                .current_dir(&self.config.src),
+        );
+
+        // Try passing `--progress` to start, then run git again without if that fails.
+        let update = |progress: bool| {
+            let mut git = Command::new("git");
+            git.args(&["submodule", "update", "--init", "--recursive"]);
+            if progress {
+                git.arg("--progress");
+            }
+            git.arg(relative_path).current_dir(&self.config.src);
+            git
+        };
+        // NOTE: doesn't use `try_run` because this shouldn't print an error if it fails.
+        if !update(true).status().map_or(false, |status| status.success()) {
+            self.run(&mut update(false));
+        }
+
+        self.run(Command::new("git").args(&["reset", "-q", "--hard"]).current_dir(&absolute_path));
+        self.run(Command::new("git").args(&["clean", "-qdfx"]).current_dir(absolute_path));
+    }
+
+    /// If any submodule has been initialized already, sync it unconditionally.
+    /// This avoids contributors checking in a submodule change by accident.
+    pub fn maybe_update_submodules(&self) {
+        // WARNING: keep this in sync with the submodules hard-coded in bootstrap.py
+        const BOOTSTRAP_SUBMODULES: &[&str] = &[
+            "src/tools/rust-installer",
+            "src/tools/cargo",
+            "src/tools/rls",
+            "src/tools/miri",
+            "library/backtrace",
+            "library/stdarch",
+        ];
+        // Avoid running git when there isn't a git checkout.
+        if !self.config.submodules {
+            return;
+        }
+        let output = output(
+            Command::new("git")
+                .args(&["config", "--file"])
+                .arg(&self.config.src.join(".gitmodules"))
+                .args(&["--get-regexp", "path"]),
+        );
+        for line in output.lines() {
+            // Look for `submodule.$name.path = $path`
+            // Sample output: `submodule.src/rust-installer.path src/tools/rust-installer`
+            let submodule = Path::new(line.splitn(2, ' ').nth(1).unwrap());
+            // avoid updating submodules twice
+            if !BOOTSTRAP_SUBMODULES.iter().any(|&p| Path::new(p) == submodule)
+                && channel::GitInfo::new(false, submodule).is_git()
+            {
+                self.update_submodule(submodule);
+            }
+        }
+    }
+
     /// Executes the entire build, as configured by the flags and configuration.
     pub fn build(&mut self) {
         unsafe {
             job::setup(self);
         }
 
-        // If the LLVM submodule has been initialized already, sync it unconditionally. This avoids
-        // contributors checking in a submodule change by accident.
-        if self.in_tree_llvm_info.is_git() {
-            native::update_llvm_submodule(self);
-        }
+        self.maybe_update_submodules();
 
         if let Subcommand::Format { check, paths } = &self.config.cmd {
             return format::format(self, *check, &paths);

src/bootstrap/native.rs

@@ -21,7 +21,7 @@ use build_helper::{output, t};
 use crate::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::config::TargetSelection;
 use crate::util::{self, exe};
-use crate::{Build, GitRepo};
+use crate::GitRepo;
 use build_helper::up_to_date;
 
 pub struct Meta {
@@ -91,86 +91,6 @@ pub fn prebuilt_llvm_config(
     Err(Meta { stamp, build_llvm_config, out_dir, root: root.into() })
 }
 
-// modified from `check_submodule` and `update_submodule` in bootstrap.py
-pub(crate) fn update_llvm_submodule(build: &Build) {
-    let llvm_project = &Path::new("src").join("llvm-project");
-
-    fn dir_is_empty(dir: &Path) -> bool {
-        t!(std::fs::read_dir(dir)).next().is_none()
-    }
-
-    if !build.config.submodules {
-        return;
-    }
-
-    // NOTE: The check for the empty directory is here because when running x.py
-    // the first time, the llvm submodule won't be checked out. Check it out
-    // now so we can build it.
-    if !build.in_tree_llvm_info.is_git() && !dir_is_empty(&build.config.src.join(llvm_project)) {
-        return;
-    }
-
-    // check_submodule
-    if build.config.fast_submodules {
-        let checked_out_hash = output(
-            Command::new("git")
-                .args(&["rev-parse", "HEAD"])
-                .current_dir(build.config.src.join(llvm_project)),
-        );
-        // update_submodules
-        let recorded = output(
-            Command::new("git")
-                .args(&["ls-tree", "HEAD"])
-                .arg(llvm_project)
-                .current_dir(&build.config.src),
-        );
-        let actual_hash = recorded
-            .split_whitespace()
-            .nth(2)
-            .unwrap_or_else(|| panic!("unexpected output `{}`", recorded));
-
-        // update_submodule
-        if actual_hash == checked_out_hash.trim_end() {
-            // already checked out
-            return;
-        }
-    }
-
-    println!("Updating submodule {}", llvm_project.display());
-    build.run(
-        Command::new("git")
-            .args(&["submodule", "-q", "sync"])
-            .arg(llvm_project)
-            .current_dir(&build.config.src),
-    );
-
-    // Try passing `--progress` to start, then run git again without if that fails.
-    let update = |progress: bool| {
-        let mut git = Command::new("git");
-        git.args(&["submodule", "update", "--init", "--recursive"]);
-        if progress {
-            git.arg("--progress");
-        }
-        git.arg(llvm_project).current_dir(&build.config.src);
-        git
-    };
-    // NOTE: doesn't use `try_run` because this shouldn't print an error if it fails.
-    if !update(true).status().map_or(false, |status| status.success()) {
-        build.run(&mut update(false));
-    }
-
-    build.run(
-        Command::new("git")
-            .args(&["reset", "-q", "--hard"])
-            .current_dir(build.config.src.join(llvm_project)),
-    );
-    build.run(
-        Command::new("git")
-            .args(&["clean", "-qdfx"])
-            .current_dir(build.config.src.join(llvm_project)),
-    );
-}
-
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct Llvm {
     pub target: TargetSelection,
@@ -208,9 +128,7 @@ impl Step for Llvm {
                 Err(m) => m,
             };
 
-        if !builder.config.dry_run {
-            update_llvm_submodule(builder);
-        }
+        builder.update_submodule(&Path::new("src").join("llvm-project"));
         if builder.config.llvm_link_shared
             && (target.contains("windows") || target.contains("apple-darwin"))
         {