Fix mozjs-sys always being out of date (#524)

* Fix mozjs-sys always being out of date

- `src/rustfmt.toml` does not exist, so always out of date
- the configure script is touched by the makefile, so the
  second build will always be out of date, even without changes.
- bindgen::CargoCallbacks will by default tell Cargo to rerun
  the build-script if any of the included files change.
  In our case some of the included files are generated by the
  build-script, so their mtime will always be newer than
  when the build-script last ran causing cargo to needlessly
  rerun the build-script.
  Writing a customized Callback that ignores generated include
  files avoids this problem

Signed-off-by: Jonathan Schwender <[email protected]>

* Bump mozjs_sys to 128.3-5

Signed-off-by: Jonathan Schwender <[email protected]>

---------

Signed-off-by: Jonathan Schwender <[email protected]>
Signed-off-by: Jonathan Schwender <[email protected]>

mozjs-sys/Cargo.toml

@@ -2,7 +2,7 @@
 name = "mozjs_sys"
 description = "System crate for the Mozilla SpiderMonkey JavaScript engine."
 repository.workspace = true
-version = "0.128.3-4"
+version = "0.128.3-5"
 authors = ["Mozilla"]
 links = "mozjs"
 build = "build.rs"

mozjs-sys/build.rs

@@ -2,6 +2,7 @@
  * 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 bindgen::callbacks::ParseCallbacks;
 use bindgen::Formatter;
 use flate2::read::GzDecoder;
 use flate2::write::GzEncoder;
@@ -55,8 +56,7 @@ const SM_TARGET_ENV_VARS: &'static [&'static str] = &[
     "OBJCOPY",
 ];
 
-const EXTRA_FILES: &'static [&'static str] =
-    &["makefile.cargo", "src/rustfmt.toml", "src/jsapi.cpp"];
+const EXTRA_FILES: &'static [&'static str] = &["makefile.cargo", "src/jsapi.cpp"];
 
 /// Which version of moztools we expect
 #[cfg(windows)]
@@ -647,6 +647,10 @@ fn ignore(path: &Path) -> bool {
         return true;
     }
 
+    if path.ends_with("js/src/configure") {
+        return true;
+    }
+
     let ignored_extensions = ["pyc", "o", "so", "dll", "dylib"];
 
     path.extension().map_or(false, |extension| {
@@ -656,7 +660,37 @@ fn ignore(path: &Path) -> bool {
     })
 }
 
+/// Customization of [`bindgen::CargoCallbacks`]
+///
+/// This accounts for generated header files, to prevent needless rebuilds
+#[derive(Debug)]
+struct CustomCargoCallbacks;
+
+impl CustomCargoCallbacks {
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+impl ParseCallbacks for CustomCargoCallbacks {
+    fn header_file(&self, filename: &str) {
+        println!("cargo:rerun-if-changed={}", filename);
+    }
+    fn include_file(&self, filename: &str) {
+        // These header files are generated by the build-script
+        // so cargo checking for changes would only cause needless rebuilds.
+        if !filename.contains("dist/include") {
+            println!("cargo:rerun-if-changed={}", filename);
+        }
+    }
+
+    fn read_env_var(&self, key: &str) {
+        println!("cargo:rerun-if-env-changed={}", key);
+    }
+}
+
 mod jsglue {
+    use crate::CustomCargoCallbacks;
     use std::env;
     use std::path::{Path, PathBuf};
 
@@ -692,12 +726,13 @@ mod jsglue {
     pub fn build(outdir: &Path) {
         //let mut build = cxx_build::bridge("src/jsglue.rs"); // returns a cc::Build;
         let mut build = cc::Build::new();
-        let include_path: PathBuf = outdir.join("dist/include");
+        let include_path = outdir.join("dist/include");
 
         build
             .cpp(true)
             .file("src/jsglue.cpp")
             .include(&include_path);
+
         for flag in cc_flags(false) {
             build.flag_if_supported(flag);
         }
@@ -725,7 +760,7 @@ mod jsglue {
         println!("cargo:rerun-if-changed=src/jsglue.cpp");
         let mut builder = bindgen::Builder::default()
             .header("./src/jsglue.cpp")
-            .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
+            .parse_callbacks(Box::new(CustomCargoCallbacks::new()))
             .size_t_is_usize(true)
             .formatter(bindgen::Formatter::Rustfmt)
             .clang_arg("-x")