Bug 1751331 - Add a mozbuild crate that exposes some build configuration...

Bug 1751331 - Add a mozbuild crate that exposes some build configuration items. r=firefox-build-system-reviewers,andi

This will be used as a central point of authority rather than individual
crates figuring things out on their own.

Differential Revision: https://phabricator.services.mozilla.com/D136558

Cargo.lock

@@ -6019,3 +6019,7 @@ dependencies = [
  "podio",
  "time",
 ]
+
+[[patch.unused]]
+name = "mozbuild"
+version = "0.1.0"

Cargo.toml

@@ -86,6 +86,9 @@ opt-level = 2
 cmake = { path = "build/rust/cmake" }
 vcpkg = { path = "build/rust/vcpkg" }
 
+# Helper crate for integration in the gecko build system.
+mozbuild = { path = "build/rust/mozbuild" }
+
 # Patch autocfg to hide rustc output. Workaround for https://github.com/cuviper/autocfg/issues/30
 autocfg = { path = "third_party/rust/autocfg" }
 

build/moz.build

@@ -21,6 +21,9 @@ else:
 if CONFIG["MOZ_STDCXX_COMPAT"]:
     DIRS += ["unix/stdc++compat"]
 
+if CONFIG["RUSTC"]:
+    DIRS += ["rust/mozbuild"]
+
 CRAMTEST_MANIFESTS += [
     "tests/cram/cram.ini",
 ]

build/rust/mozbuild/Cargo.toml

+[package]
+name = "mozbuild"
+version = "0.1.0"
+edition = "2018"
+license = "MPL-2.0"
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+once_cell = "1"

build/rust/mozbuild/build.rs

+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::path::PathBuf;
+
+fn main() {
+    let out_dir = PathBuf::from(std::env::var_os("OUT_DIR").unwrap());
+    if let Some(topobjdir) = out_dir
+        .ancestors()
+        .find(|dir| dir.join("config.status").exists())
+    {
+        println!(
+            "cargo:rustc-env=BUILDCONFIG_RS={}",
+            topobjdir
+                .join("build/rust/mozbuild/buildconfig.rs")
+                .display()
+        );
+    }
+}

build/rust/mozbuild/generate_buildconfig.py

+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import buildconfig
+
+
+def generate_bool(name):
+    value = buildconfig.substs.get(name)
+    return f"pub const {name}: bool = {'true' if value else 'false'};\n"
+
+
+def generate(output):
+    output.write(generate_bool("MOZ_FOLD_LIBS"))
+    output.write(generate_bool("NIGHTLY_BUILD"))
+    output.write(generate_bool("RELEASE_OR_BETA"))
+    output.write(generate_bool("EARLY_BETA_OR_EARLIER"))
+    output.write(generate_bool("MOZ_DEV_EDITION"))
+    output.write(generate_bool("MOZ_ESR"))
+    output.write(generate_bool("MOZ_DIAGNOSTIC_ASSERT_ENABLED"))

build/rust/mozbuild/lib.rs

+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use once_cell::sync::Lazy;
+use std::env;
+use std::path::PathBuf;
+
+pub static TOPOBJDIR: Lazy<PathBuf> = Lazy::new(|| {
+    let path = PathBuf::from(
+        env::var_os("MOZ_TOPOBJDIR").expect("MOZ_TOPOBJDIR must be set in the environment"),
+    );
+    assert!(
+        path.is_absolute() && path.is_dir(),
+        "MOZ_TOPOBJDIR must be an absolute directory, was: {}",
+        path.display()
+    );
+    path
+});
+
+#[macro_export]
+macro_rules! objdir_path {
+    ($path:literal) => {
+        concat!(env!("MOZ_TOPOBJDIR"), "/", $path)
+    };
+}
+
+pub static TOPSRCDIR: Lazy<PathBuf> = Lazy::new(|| {
+    let path =
+        PathBuf::from(env::var_os("MOZ_SRC").expect("MOZ_SRC must be set in the environment"));
+    assert!(
+        path.is_absolute() && path.is_dir(),
+        "MOZ_SRC must be an absolute directory, was: {}",
+        path.display()
+    );
+    path
+});
+
+pub mod config {
+    include!(env!("BUILDCONFIG_RS"));
+}

build/rust/mozbuild/moz.build

+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+GeneratedFile(
+    "buildconfig.rs", script="generate_buildconfig.py", entry_point="generate"
+)