Rename build script rather and include it as bytes

src/util/common.rs

@@ -4,9 +4,9 @@ use anyhow::{anyhow, bail, ensure, Context, Result};
 use once_cell::sync::Lazy;
 use std::{
     env,
-    fs::{canonicalize, set_permissions, Permissions},
+    fs::canonicalize,
     io::Write,
-    os::unix::{ffi::OsStrExt, fs::PermissionsExt},
+    os::unix::ffi::OsStrExt,
     path::Path,
     process::{Command, Output, Stdio},
     str::Utf8Error,
@@ -29,8 +29,8 @@ const DEFAULT_PROFILE: &str = r#"(version 1)
 /// Executes `command`, forwards its output to stdout and stderr, and optionally checks whether
 /// `command` succeeded.
 ///
-/// Called by [`unpack_and_exec`]. Since this file is included in the wrapper build script's
-/// src/main.rs file, `exec_forwarding_output` should appear here, alongside [`unpack_and_exec`].
+/// Called by [`exec_sibling`]. Since this file is included in the wrapper build script's
+/// src/main.rs file, `exec_forwarding_output` should appear here, alongside [`exec_sibling`].
 ///
 /// # Errors
 ///
@@ -63,15 +63,16 @@ pub fn exec_forwarding_output(mut command: Command, failure_is_error: bool) -> R
 /// Essentially the body of the wrapper build script's `main` function. Not called by `build-wrap`
 /// itself.
 #[allow(dead_code)]
-fn unpack_and_exec(bytes: &[u8]) -> Result<()> {
-    let (mut file, temp_path) =
-        tempfile::NamedTempFile::new().map(tempfile::NamedTempFile::into_parts)?;
+fn exec_sibling(sibling_path_as_str: &str) -> Result<()> {
+    let current_exe = env::current_exe()?;
 
-    file.write_all(bytes)?;
+    let parent = current_exe
+        .parent()
+        .ok_or_else(|| anyhow!("failed to get `current_exe` parent"))?;
 
-    drop(file);
+    let sibling_path = Path::new(sibling_path_as_str);
 
-    set_permissions(&temp_path, Permissions::from_mode(0o755))?;
+    assert!(sibling_path.starts_with(parent));
 
     // smoelius: The `BUILD_WRAP_CMD` used is the one set when set when the wrapper build script is
     // compiled, not when it is run. So if the wrapped build script prints the following and the
@@ -81,7 +82,7 @@ fn unpack_and_exec(bytes: &[u8]) -> Result<()> {
     // cargo:rerun-if-env-changed=BUILD_WRAP_CMD
     // ```
     // They will cause the wrapped build script to be rerun, however.
-    let expanded_args = split_and_expand(&temp_path)?;
+    let expanded_args = split_and_expand(sibling_path)?;
 
     let allow_enabled = enabled("BUILD_WRAP_ALLOW");
 
@@ -93,12 +94,10 @@ fn unpack_and_exec(bytes: &[u8]) -> Result<()> {
     // `BUILD_WRAP_ALLOW` is enabled.
     if !output.status.success() {
         debug_assert!(allow_enabled);
-        let command = Command::new(&temp_path);
+        let command = Command::new(sibling_path);
         let _: Output = exec_forwarding_output(command, true)?;
     }
 
-    drop(temp_path);
-
     Ok(())
 }
 

src/wrapper.rs

@@ -1,22 +1,32 @@
 use crate::util::ToUtf8;
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use std::{
-    fs::{create_dir, write},
+    fs::{create_dir, rename, write},
     path::Path,
 };
-use tempfile::{tempdir, TempDir};
+use tempfile::{tempdir, NamedTempFile, TempDir};
 
 #[allow(clippy::disallowed_methods)]
 pub fn package(build_script_path: &Path) -> Result<TempDir> {
-    let build_script_path_as_str = build_script_path.to_utf8()?;
+    let parent = build_script_path
+        .parent()
+        .ok_or_else(|| anyhow!("failed to get `build_script_path` parent"))?;
+
+    let temp_file = NamedTempFile::new_in(parent)?;
+
+    let (_file, sibling_path) = temp_file.keep()?;
+
+    rename(build_script_path, &sibling_path)?;
+
+    let sibling_path_as_str = sibling_path.to_utf8()?;
 
     let tempdir = tempdir()?;
 
     write(tempdir.path().join("Cargo.toml"), CARGO_TOML)?;
     create_dir(tempdir.path().join("src"))?;
     write(
         tempdir.path().join("src/main.rs"),
-        main_rs(build_script_path_as_str),
+        main_rs(sibling_path_as_str),
     )?;
 
     Ok(tempdir)
@@ -39,19 +49,19 @@ tempfile = "3.10"
 /// A wrapper build script's src/main.rs consists of the following:
 ///
 /// - the contents of util/common.rs (included verbatim)
-/// - the original build script as a byte slice (`BYTES`)
+/// - the path of the renamed original build script (`PATH`)
 /// - a `main` function
 ///
 /// See [`package`].
-fn main_rs(build_script_path_as_str: &str) -> Vec<u8> {
+fn main_rs(sibling_path_as_str: &str) -> Vec<u8> {
     [
         COMMON_RS,
         format!(
             r#"
-const BYTES: &[u8] = include_bytes!("{build_script_path_as_str}");
+const PATH: &str = "{sibling_path_as_str}";
 
 fn main() -> Result<()> {{
-    unpack_and_exec(BYTES)
+    exec_sibling(PATH)
 }}
 "#,
         )

tests/integration/cargo_config.rs

@@ -1,5 +1,5 @@
 use crate::util;
-use std::{env::temp_dir, path::Path, process::Command};
+use std::{path::Path, process::Command};
 
 const DIR: &str = "fixtures/cargo_config";
 
@@ -16,8 +16,19 @@ fn cargo_config() {
     // smoelius: When `build-wrap` builds the wrapper package, it expects the target directory to be
     // `target`. So building the wrapper package in `fixtures/cargo_config` would fail because it
     // contains a `.cargo/config.toml` that sets the target directory to `target-custom`.
+
+    // smoelius: The build script in `fixtures/cargo_config` prints the path of the current
+    // executable, i.e., the wrapped, original build script. Previously, this was unpacked into
+    // `std::env::temp_dir()`. However, `build-wrap` now renames the original build script so that
+    // it is a sibling of the wrapper build script. Hence, when this test is run, the current
+    // executable should be in `target-custom` alongside the wrapper build script.
     let command = util::build_with_build_wrap();
-    test_build(command, &temp_dir());
+    test_build(
+        command,
+        &Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join(DIR)
+            .join("target-custom/debug"),
+    );
 }
 
 fn test_build(mut command: Command, expected_dir: &Path) {