[workerd-cxx] eliminate source copying (#28)

* [workerd-cxx] eliminate source copying

The original cxx crate uses symlinks to share code between its
sub-crates. I assume this is because of cargo limitation that
forces you to share such shared code as an independent crate that
anyone can use.

Symlinks don't work well on windows, so we got rid of them by copying
the code during compilation. This has the unfortunate effect of
rust-analyzer (and other tools) not working properly.

We currently consume workerd-cxx only through bazel and we do not
have such limitations.

This change eliminates the copy and adjusts visibilities (and some
minor detail of implementation) for things to compile.

I hope that usability gains will overweight the additional merge
difficulties.

* clippy

Author: mikea

BUILD.bazel

@@ -1,7 +1,5 @@
 load("@rules_cc//cc:defs.bzl", "cc_library")
 load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_library", "rust_proc_macro")
-load("@bazel_skylib//lib:paths.bzl", "paths")
-load(":copy_srcs.bzl", "copy_srcs")
 
 rust_library(
     name = "cxx",
@@ -27,17 +25,41 @@ alias(
     visibility = ["//visibility:public"],
 )
 
-copy_srcs(
-    name = "cxxbridge-cmd-srcs",
-    srcs = glob(["gen/cmd/src/*.rs"])
+rust_library(
+    name = "syntax",
+    srcs = glob(["syntax/*.rs"]),
+    crate_root = "syntax/mod.rs",
+    edition = "2021",
+    deps = [
+        "@crates.io//:proc-macro2",
+        "@crates.io//:quote",
+        "@crates.io//:syn",
+    ],
+)
+
+rust_library(
+    name = "gen",
+    srcs = glob(["gen/src/*.rs"]),
+    compile_data = ["include/cxx.h"],
+    crate_root = "gen/src/mod.rs",
+    edition = "2021",
+    deps = [
+        ":syntax",
+        "@crates.io//:codespan-reporting",
+        "@crates.io//:proc-macro2",
+        "@crates.io//:quote",
+        "@crates.io//:syn",
+    ],
 )
 
 rust_binary(
     name = "cxxbridge",
-    srcs = [":cxxbridge-cmd-srcs"],
+    srcs = glob(["gen/cmd/src/*.rs"]),
     compile_data = ["include/cxx.h"],
     edition = "2021",
     deps = [
+        ":gen",
+        ":syntax",
         "@crates.io//:clap",
         "@crates.io//:codespan-reporting",
         "@crates.io//:proc-macro2",
@@ -61,38 +83,32 @@ cc_library(
     linkstatic = True,
 )
 
-copy_srcs(
-    name = "cxxbridge-macro-srcs",
-    srcs = glob(["macro/src/*.rs"])
-)
-
 rust_proc_macro(
     name = "cxxbridge-macro",
-    srcs = [":cxxbridge-macro-srcs"],
+    srcs = glob(["macro/src/*.rs"]),
     edition = "2021",
     proc_macro_deps = [
         "@crates.io//:rustversion",
     ],
     deps = [
+        ":gen",
+        ":syntax",
         "@crates.io//:proc-macro2",
         "@crates.io//:quote",
         "@crates.io//:syn",
     ],
 )
 
-copy_srcs(
-    name = "cxx-build-srcs",
-    srcs = glob(["gen/build/src/*.rs"])
-)
-
 rust_library(
     name = "cxx-build",
-    srcs = [":cxx-build-srcs"],
+    srcs = glob(["gen/build/src/*.rs"]),
     compile_data = [
         "include/cxx.h",
     ],
     edition = "2021",
     deps = [
+        ":gen",
+        ":syntax",
         "@crates.io//:cc",
         "@crates.io//:codespan-reporting",
         "@crates.io//:proc-macro2",
@@ -102,20 +118,16 @@ rust_library(
     ],
 )
 
-copy_srcs(
-    name = "cxx-gen-srcs",
-    srcs = glob(["gen/lib/src/*.rs"])
-)
-
 rust_library(
     name = "cxx-gen",
-    srcs = [":cxx-gen-srcs"],
+    srcs = glob(["gen/lib/src/*.rs"]),
     compile_data = ["include/cxx.h"],
     edition = "2021",
     visibility = ["//visibility:public"],
     deps = [
+        ":gen",
+        ":syntax",
         "@crates.io//:cc",
-        "@crates.io//:codespan-reporting",
         "@crates.io//:proc-macro2",
         "@crates.io//:quote",
         "@crates.io//:syn",

copy_srcs.bzl

@@ -1,4 +1,4 @@
-use crate::gen::{CfgEvaluator, CfgResult};
+use gen::{CfgEvaluator, CfgResult};
 use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::collections::{BTreeMap as Map, BTreeSet as Set};

gen/build/src/cargo.rs

@@ -342,7 +342,7 @@ pub use self::r#impl::Cfg::CFG;
 #[cfg(not(doc))]
 mod r#impl {
     use crate::intern::{intern, InternedString};
-    use crate::syntax::map::UnorderedMap as Map;
+    use syntax::map::UnorderedMap as Map;
     use crate::vec::{self, InternedVec as _};
     use std::cell::RefCell;
     use std::fmt::{self, Debug};

gen/build/src/cfg.rs

@@ -1,5 +1,5 @@
 use crate::cfg::CFG;
-use crate::gen::fs;
+use gen::fs;
 use std::error::Error as StdError;
 use std::ffi::OsString;
 use std::fmt::{self, Display};

gen/build/src/error.rs

@@ -1,4 +1,4 @@
-use crate::syntax::set::UnorderedSet as Set;
+use syntax::set::UnorderedSet as Set;
 use std::sync::{Mutex, OnceLock, PoisonError};
 
 #[derive(Copy, Clone, Default)]

gen/build/src/intern.rs

@@ -81,21 +81,19 @@ mod cargo;
 mod cfg;
 mod deps;
 mod error;
-mod gen;
 mod intern;
 mod out;
 mod paths;
-mod syntax;
 mod target;
 mod vec;
 
 use crate::cargo::CargoEnvCfgEvaluator;
 use crate::deps::{Crate, HeaderDir};
 use crate::error::{Error, Result};
-use crate::gen::error::report;
-use crate::gen::Opt;
+use gen::error::report;
+use gen::Opt;
 use crate::paths::PathExt;
-use crate::syntax::map::{Entry, UnorderedMap};
+use syntax::map::{Entry, UnorderedMap};
 use crate::target::TargetDir;
 use cc::Build;
 use std::collections::BTreeSet;
@@ -425,7 +423,7 @@ fn generate_bridge(prj: &Project, build: &mut Build, rust_source_file: &Path) ->
 }
 
 fn best_effort_copy_headers(src: &Path, dst: &Path, max_depth: usize) {
-    // Not using crate::gen::fs because we aren't reporting the errors.
+    // Not using gen::fs because we aren't reporting the errors.
     use std::fs;
 
     let mut dst_created = false;

gen/build/src/lib.rs

@@ -1,5 +1,5 @@
 use crate::error::{Error, Result};
-use crate::gen::fs;
+use gen::fs;
 use crate::paths;
 use std::path::{Component, Path, PathBuf};
 use std::{env, io};

gen/build/src/out.rs

@@ -1,5 +1,5 @@
 use crate::error::Result;
-use crate::gen::fs;
+use gen::fs;
 use std::ffi::OsStr;
 use std::path::{Component, Path, PathBuf};
 

gen/build/src/paths.rs

@@ -4,8 +4,8 @@ mod test;
 
 use super::{Opt, Output};
 use crate::cfg::{self, CfgValue};
-use crate::gen::include::Include;
-use crate::syntax::IncludeKind;
+use gen::include::Include;
+use syntax::IncludeKind;
 use clap::builder::{ArgAction, ValueParser};
 use clap::{Arg, Command};
 use std::collections::{BTreeMap as Map, BTreeSet as Set};