bugfix: generated js and css filenames were incorrect

The resource hashes were computed before closing the resource files themselves, creating invalid hashes

That, in turn, caused incorrect file caching, and prevented resource updates in browsers

build.rs

@@ -21,6 +21,15 @@ fn inline_dependencies(path_in: &str, path_out: &Path) {
     // the URL in the generated file.
     println!("cargo:rerun-if-changed={}", path_in);
     let original = File::open(path_in).unwrap();
+    process_input_file(path_out, original);
+    std::fs::write(
+        format!("{}.filename.txt", path_out.display()),
+        hashed_filename(path_out),
+    )
+    .unwrap();
+}
+
+fn process_input_file(path_out: &Path, original: File) {
     let mut outfile = BufWriter::new(File::create(path_out).unwrap());
     for l in BufReader::new(original).lines() {
         let line = l.unwrap();
@@ -36,11 +45,6 @@ fn inline_dependencies(path_in: &str, path_out: &Path) {
             writeln!(outfile, "{}", line).unwrap();
         }
     }
-    std::fs::write(
-        format!("{}.filename.txt", path_out.display()),
-        hashed_filename(path_out),
-    )
-    .unwrap();
 }
 
 // Given a filename, creates a new unique filename based on the file contents
@@ -48,7 +52,10 @@ fn hashed_filename(path: &Path) -> String {
     let mut file = File::open(path).unwrap();
     let mut buf = [0u8; 4096];
     let mut hasher = DefaultHasher::new();
-    while let Ok(bytes_read) = file.read(&mut buf) {
+    loop {
+        let bytes_read = file
+            .read(&mut buf)
+            .expect(&format!("error reading {}", path.display()));
         if bytes_read == 0 {
             break;
         }