chore: copy rust lib only when it changes

rust/xtask/src/install_dependency.rs

@@ -156,6 +156,31 @@ pub fn get_godot_executable_path() -> Option<String> {
     Some(os_url)
 }
 
+fn copy_if_modified<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dest: Q) -> io::Result<()> {
+    let src_path = src.as_ref();
+    let dest_path = dest.as_ref();
+
+    // Obtain the metadata of the source and destination file
+    let metadata_src = fs::metadata(src_path);
+    let metadata_dest = fs::metadata(dest_path);
+
+    // If both files exist, we compare their modification times
+    if metadata_src.is_ok() && metadata_dest.is_ok() {
+        let time_src = metadata_src?.modified()?;
+        let time_dest = metadata_dest?.modified()?;
+
+        // If the destination file is more recent or equal to the source file, we do not copy
+        if time_dest >= time_src {
+            println!("Skip copy, equal file {}", dest_path.to_string_lossy());
+            return Ok(());
+        }
+    }
+
+    // If the destination file does not exist or is older, we copy the source file to the destination
+    fs::copy(src_path, dest_path).map(|_| println!("Copying {}", dest_path.to_string_lossy()))?;
+    Ok(())
+}
+
 pub fn copy_library(debug_mode: bool) -> Result<(), anyhow::Error> {
     let os = env::consts::OS;
     let arch = env::consts::ARCH;
@@ -174,14 +199,14 @@ pub fn copy_library(debug_mode: bool) -> Result<(), anyhow::Error> {
     };
 
     let source_folder = format!("{RUST_LIB_PROJECT_FOLDER}{source_folder}");
-    println!("Copying {source_folder:?}");
+
     let source_file =
         adjust_canonicalization(fs::canonicalize(source_folder)?.join(file_name.clone()));
 
     let lib_folder = format!("{GODOT_PROJECT_FOLDER}lib/");
     let destination_file =
         adjust_canonicalization(fs::canonicalize(lib_folder.as_str())?.join(file_name));
-    fs::copy(source_file, destination_file)?;
+    copy_if_modified(source_file, destination_file)?;
 
     copy_ffmpeg_libraries(lib_folder)?;
 
@@ -203,7 +228,7 @@ pub fn copy_ffmpeg_libraries(dest_folder: String) -> Result<(), anyhow::Error> {
 
                 if file_name.ends_with(".dll") {
                     let dest_path = format!("{dest_folder}{file_name}");
-                    fs::copy(entry.path(), dest_path)?;
+                    copy_if_modified(entry.path(), dest_path)?;
                 }
             }
         }