fix: do not mutate read-only files (#1155)

* fix: do not mutate read-only files

fixes #1071
related #700

* support is_writable on windows

---------

Co-authored-by: Jake Runzer <jakerunzer@gmail.com>

src/nixpacks/files.rs

@@ -2,6 +2,21 @@ use anyhow::Result;
 use ignore::WalkBuilder;
 use std::{fs, io, path::Path};
 
+#[cfg(unix)]
+fn is_writable<P: AsRef<Path>>(path: P) -> io::Result<bool> {
+ use std::os::unix::fs::PermissionsExt;
+ let metadata = fs::metadata(path)?;
+ let permissions = metadata.permissions();
+ Ok(permissions.mode() & 0o200 != 0)
+}
+
+#[cfg(windows)]
+fn is_writable<P: AsRef<Path>>(path: P) -> io::Result<bool> {
+ use std::os::windows::fs::MetadataExt;
+ let metadata = fs::metadata(path)?;
+ Ok(!metadata.file_attributes() & 1 != 0)
+}
+
 /// Copies a directory and all its contents to the destination path, recursively.
 pub fn recursive_copy_dir<T: AsRef<Path>, Q: AsRef<Path>>(source: T, dest: Q) -> Result<()> {
  let walker = WalkBuilder::new(&source)
@@ -30,9 +45,12 @@ pub fn recursive_copy_dir<T: AsRef<Path>, Q: AsRef<Path>>(source: T, dest: Q) ->
  // copy files
  else if file_type.is_file() {
  fs::copy(from, &to)?;
- // replace CRLF with LF
- if let Ok(data) = fs::read_to_string(from) {
- fs::write(&to, data.replace("\r\n", "\n"))?;
+
+ if is_writable(&to)? {
+ // replace CRLF with LF
+ if let Ok(data) = fs::read_to_string(from) {
+ fs::write(&to, data.replace("\r\n", "\n"))?;
+ }
  }
  }
  }