Merge pull request dtolnay#1087 from dtolnay/windows

Fix cxx-build on Windows when `target` dir is populated from a cache with dangling symlinks

gen/build/src/out.rs

@@ -8,7 +8,7 @@ pub(crate) fn write(path: impl AsRef<Path>, content: &[u8]) -> Result<()> {
  let path = path.as_ref();
 
  let mut create_dir_error = None;
- if path.exists() {
+ if fs::exists(path) {
  if let Ok(existing) = fs::read(path) {
  if existing == content {
  // Avoid bumping modified time with unchanged contents.
@@ -34,7 +34,7 @@ pub(crate) fn symlink_file(original: impl AsRef<Path>, link: impl AsRef<Path>) -
  let link = link.as_ref();
 
  let mut create_dir_error = None;
- if link.exists() {
+ if fs::exists(link) {
  best_effort_remove(link);
  } else {
  let parent = link.parent().unwrap();
@@ -68,7 +68,7 @@ pub(crate) fn symlink_dir(original: impl AsRef<Path>, link: impl AsRef<Path>) ->
  let link = link.as_ref();
 
  let mut create_dir_error = None;
- if link.exists() {
+ if fs::exists(link) {
  best_effort_remove(link);
  } else {
  let parent = link.parent().unwrap();
@@ -86,24 +86,34 @@ pub(crate) fn symlink_dir(original: impl AsRef<Path>, link: impl AsRef<Path>) ->
 fn best_effort_remove(path: &Path) {
  use std::fs;
 
- let file_type = match if cfg!(windows) {
+ if cfg!(windows) {
  // On Windows, the correct choice of remove_file vs remove_dir needs to
  // be used according to what the symlink *points to*. Trying to use
  // remove_file to remove a symlink which points to a directory fails
  // with "Access is denied".
- fs::metadata(path)
+ if let Ok(metadata) = fs::metadata(path) {
+ if metadata.is_dir() {
+ let _ = fs::remove_dir_all(path);
+ } else {
+ let _ = fs::remove_file(path);
+ }
+ } else if fs::symlink_metadata(path).is_ok() {
+ // The symlink might exist but be dangling, in which case there is
+ // no standard way to determine what "kind" of symlink it is. Try
+ // deleting both ways.
+ if fs::remove_dir_all(path).is_err() {
+ let _ = fs::remove_file(path);
+ }
+ }
  } else {
  // On non-Windows, we check metadata not following symlinks. All
  // symlinks are removed using remove_file.
- fs::symlink_metadata(path)
- } {
- Ok(metadata) => metadata.file_type(),
- Err(_) => return,
- };
-
- if file_type.is_dir() {
- let _ = fs::remove_dir_all(path);
- } else {
- let _ = fs::remove_file(path);
+ if let Ok(metadata) = fs::symlink_metadata(path) {
+ if metadata.is_dir() {
+ let _ = fs::remove_dir_all(path);
+ } else {
+ let _ = fs::remove_file(path);
+ }
+ }
  }
 }

gen/src/fs.rs

@@ -68,6 +68,13 @@ pub(crate) fn current_dir() -> Result<PathBuf> {
  }
 }
 
+pub(crate) fn exists(path: impl AsRef<Path>) -> bool {
+ let path = path.as_ref();
+ // If path is a symlink, this returns true, regardless of whether the
+ // symlink points to a path that exists.
+ std::fs::symlink_metadata(path).is_ok()
+}
+
 pub(crate) fn read(path: impl AsRef<Path>) -> Result<Vec<u8>> {
  let path = path.as_ref();
  match std::fs::read(path) {