From bbaf5119ed75f08aa0df2dc7311d21c5ee4f6fdb Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@meta.com>
Date: Tue, 6 Aug 2024 16:50:53 -0700
Subject: [PATCH] Synthesize build scripts that Cargo failed to vendor

Summary:
This is a workaround for [rust-lang/cargo#14348](https://github.com/rust-lang/cargo/issues/14348), which is a regression in Rust 1.80's `cargo vendor`.

4 crates in fbsource/third-party/rust are currently impacted:

- `cxx-build`
- `cxxbridge-cmd`
- `cxxbridge-macro`
- `orjson` (https://github.com/ijl/orjson)

The workaround works by writing a build.rs containing just `fn main() {}` for crates where Cargo has injected `build = "build.rs"` into their manifest without vendoring the corresponding build.rs.

We can delete this workaround once the Cargo bug is fixed.

Reviewed By: diliop

Differential Revision: D60855541

fbshipit-source-id: 553c3e45e8f0998fb3091b1f1a82f33b2d7c0a6f
---
 Cargo.lock    | 11 +++++++++
 Cargo.toml    |  1 +
 src/vendor.rs | 67 ++++++++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 353c9454..bf49b4df 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -201,6 +201,16 @@ dependencies = [
  "url",
 ]
 
+[[package]]
+name = "cargo_toml"
+version = "0.17.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a969e13a7589e9e3e4207e153bae624ade2b5622fb4684a4923b23ec3d57719"
+dependencies = [
+ "serde",
+ "toml 0.8.5",
+]
+
 [[package]]
 name = "cc"
 version = "1.0.90"
@@ -1006,6 +1016,7 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "cached",
+ "cargo_toml",
  "clap",
  "dunce",
  "env_logger",
diff --git a/Cargo.toml b/Cargo.toml
index 4618eec9..faba3354 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,6 +11,7 @@ license = "MIT"
 [dependencies]
 anyhow = "1.0.75"
 cached = "0.39.0"
+cargo_toml = "0.17.2"
 clap = { version = "4.5.11", features = ["derive", "env", "string", "unicode", "wrap_help"] }
 dunce = "1.0.2"
 env_logger = "0.10"
diff --git a/src/vendor.rs b/src/vendor.rs
index 3abde03f..ee8d5ce9 100644
--- a/src/vendor.rs
+++ b/src/vendor.rs
@@ -10,6 +10,7 @@ use std::io::ErrorKind;
 use std::path::Path;
 
 use anyhow::Context;
+use cargo_toml::OptionalFile;
 use globset::GlobBuilder;
 use globset::GlobSetBuilder;
 use ignore::gitignore::GitignoreBuilder;
@@ -70,6 +71,7 @@ pub(crate) fn cargo_vendor(
 
     if let Some(vendor_config) = &config.vendor {
         filter_checksum_files(&paths.third_party_dir, vendordir, vendor_config)?;
+        write_excluded_build_scripts(&paths.third_party_dir, vendordir)?;
     }
 
     if audit_sec {
@@ -158,8 +160,8 @@ fn filter_checksum_files(
 
     for entry in fs::read_dir(third_party_dir.join(vendordir))? {
         let entry = entry?;
-        let path = entry.path(); // full/path/to/vendor/foo-1.2.3
-        let checksum = path.join(".cargo-checksum.json"); // full/path/to/vendor/foo-1.2.3/.cargo-checksum.json
+        let manifest_dir = entry.path(); // full/path/to/vendor/foo-1.2.3
+        let checksum = manifest_dir.join(".cargo-checksum.json"); // full/path/to/vendor/foo-1.2.3/.cargo-checksum.json
 
         log::trace!("Reading checksum {}", checksum.display());
 
@@ -181,7 +183,7 @@ fn filter_checksum_files(
 
         let mut changed = false;
 
-        let pkgdir = relative_path(third_party_dir, &path); // vendor/foo-1.2.3
+        let pkgdir = relative_path(third_party_dir, &manifest_dir); // vendor/foo-1.2.3
 
         checksums.files.retain(|k, _| {
             log::trace!("{}: checking {}", checksum.display(), k);
@@ -204,3 +206,62 @@ fn filter_checksum_files(
 
     Ok(())
 }
+
+// Work around https://github.com/rust-lang/cargo/issues/14348.
+//
+// This step can be deleted if that `cargo vendor` bug is fixed in a future
+// version of Cargo.
+fn write_excluded_build_scripts(third_party_dir: &Path, vendordir: &Path) -> anyhow::Result<()> {
+    type TomlManifest = cargo_toml::Manifest<serde::de::IgnoredAny>;
+
+    let third_party_vendor = third_party_dir.join(vendordir);
+    if !third_party_vendor.try_exists()? {
+        // If there are no dependencies from a remote registry (because there
+        // are no dependencies whatsoever, or all dependencies are local path
+        // dependencies) then `cargo vendor` won't have created a "vendor"
+        // directory.
+        return Ok(());
+    }
+
+    for entry in fs::read_dir(third_party_vendor)? {
+        let entry = entry?;
+        let manifest_dir = entry.path(); // full/path/to/vendor/foo-1.2.3
+        let cargo_toml = manifest_dir.join("Cargo.toml");
+
+        log::trace!("Reading manifest {}", cargo_toml.display());
+
+        let content = match fs::read_to_string(&cargo_toml) {
+            Ok(file) => file,
+            Err(err) => {
+                log::warn!("Failed to read {}: {}", cargo_toml.display(), err);
+                continue;
+            }
+        };
+
+        let manifest: TomlManifest = match toml::from_str(&content) {
+            Ok(cs) => cs,
+            Err(err) => {
+                log::warn!("Failed to deserialize {}: {}", cargo_toml.display(), err);
+                continue;
+            }
+        };
+
+        let Some(package) = &manifest.package else {
+            continue;
+        };
+        let Some(OptionalFile::Path(build_script_path)) = &package.build else {
+            continue;
+        };
+
+        let expected_build_script = manifest_dir.join(build_script_path);
+        if !expected_build_script.try_exists()? {
+            log::trace!(
+                "Synthesizing build script {}",
+                expected_build_script.display(),
+            );
+            fs::write(expected_build_script, "fn main() {}\n")?;
+        }
+    }
+
+    Ok(())
+}