build.rs: re-run after any file inside directories have changed

this is needed to regenerate the build timestamp properly

build.rs

@@ -1,28 +1,43 @@
 extern crate serde_json;
 
+use std::fs;
 use std::io::prelude::*;
 use std::time::*;
 
 fn main() {
     println!("cargo:rerun-if-changed=config.json");
-    println!("cargo:rerun-if-changed=src");
-    println!("cargo:rerun-if-changed=theme");
     println!("cargo:rerun-if-changed=Cargo.toml");
+    rerun_if_dir_changed("src");
+    rerun_if_dir_changed("theme");
     // Load theme name from config.json and output code to load the theme via include_dir!
     let config: serde_json::Value = 
-        serde_json::from_str(&std::fs::read_to_string("./config.json").unwrap()).unwrap();
+        serde_json::from_str(&fs::read_to_string("./config.json").unwrap()).unwrap();
 
     generate_build_timestamp();
     generate_theme_loader(&config);
     generate_hljs_loader(&config);
 }
 
+fn rerun_if_dir_changed(dir: &str) {
+    for f in fs::read_dir(dir).unwrap() {
+        let f = f.unwrap();
+        let t = f.file_type().unwrap();
+        let path = f.path();
+        let path = path.to_str().unwrap();
+        println!("cargo:rerun-if-changed={}", path);
+
+        if t.is_dir() {
+            rerun_if_dir_changed(path);
+        }
+    }
+}
+
 fn generate_build_timestamp() {
     let build_time = format!(
         "pub const BUILD_TIMESTAMP: u64 = {};",
         SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap().as_secs());
     let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
-    let mut out_file = std::fs::File::create(out_path.join("build_timestamp.rs")).unwrap();
+    let mut out_file = fs::File::create(out_path.join("build_timestamp.rs")).unwrap();
     out_file.write(build_time.as_bytes()).unwrap();
     out_file.sync_data().unwrap();
 }
@@ -34,7 +49,7 @@ fn generate_theme_loader(config: &serde_json::Value) {
     };
     let theme_load_code = format!("const THEME_DIR: Dir = include_dir!(\"theme/{}\");", theme_name.as_str().unwrap());
     let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
-    let mut out_file = std::fs::File::create(out_path.join("load_theme.rs")).unwrap();
+    let mut out_file = fs::File::create(out_path.join("load_theme.rs")).unwrap();
     out_file.write_all(theme_load_code.as_bytes()).unwrap();
     out_file.sync_data().unwrap();
 }
@@ -58,10 +73,10 @@ fn generate_hljs_loader(config: &serde_json::Value) {
     let js_code = format!(
         "const hljs = require(\\\"highlight.js/lib/highlight.js\\\");\n{}module.exports = hljs;",
         highlight_lang);
-    let rs_code = std::fs::read_to_string("./src/hljs_tpl.rs").unwrap();
+    let rs_code = fs::read_to_string("./src/hljs_tpl.rs").unwrap();
     let rs_code = format!("#[wasm_bindgen(inline_js = \"{}\")]\n{}", js_code, rs_code);
     let out_path = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
-    let mut out_file = std::fs::File::create(out_path.join("load_hljs.rs")).unwrap();
+    let mut out_file = fs::File::create(out_path.join("load_hljs.rs")).unwrap();
     out_file.write_all(rs_code.as_bytes()).unwrap();
     out_file.sync_data().unwrap();
 }