fix: support running embedded_path! from a "remote" crate

This includes if cargo is building a crate that depends on some crates.io or git
repo crate that contains embedded assets.

crates/bevy_asset/src/io/embedded/mod.rs

@@ -108,12 +108,57 @@ macro_rules! embedded_path {
  }};
 
  ($source_path: expr, $path_str: expr) => {{
- let crate_name = module_path!().split(':').next().unwrap();
- let file_path = std::path::Path::new(file!());
- let after_src = file_path
- .strip_prefix($source_path)
- .unwrap_or_else(|_| panic!("{file_path:?} does not have prefix {}", $source_path));
+ /// Strip `src_path` from `file_path` and return only the suffix that
+ /// follows.
+ fn split_path(
+ src_path: &std::path::Path,
+ file_path: &std::path::Path,
+ ) -> std::path::PathBuf {
+ if file_path.is_absolute() {
+ // Absolute paths show up if this macro is being invoked by an
+ // external dependency, e.g. one that's being checked out from a
+ // crates repo or git.
+ //
+ // It's possible that `file_path` includes some components
+ // preceding `src_path`. For example:
+ //
+ // src_path = src
+ // file_path = /path/to/crate/src/foo.rs
+ //
+ // We want to return "foo.rs".
+ //
+ // # stupid edge case
+ //
+ // There is an annoying edge case where if `src_path` shows up
+ // twice after the workspace root:
+ //
+ // src_path = src
+ // file_path = /path/to/crate/src/src/foo.rs
+ //
+ // Then we won't know which one is legit. We can't fix this case
+ // without knowing the actual path to the external crate.
+ let mut maybe_parent = file_path.parent();
+ while let Some(parent) = maybe_parent {
+ if parent.ends_with(src_path) {
+ return file_path.strip_prefix(parent).unwrap().into();
+ }
+ maybe_parent = parent.parent();
+ }
+ panic!("Failed to find src_path {src_path:?} in {file_path:?}")
+ } else {
+ // Relative paths show up if this macro is being invoked by a
+ // local crate. In this case we know the relative path is a sub-
+ // path of the workspace root.
+ file_path
+ .strip_prefix(src_path)
+ .unwrap_or_else(|_| panic!("{file_path:?} does not have prefix {src_path:?}"))
+ .into()
+ }
+ }
+
+ let after_src = split_path($source_path.as_ref(), file!().as_ref());
  let file_path = after_src.parent().unwrap().join($path_str);
+ let crate_name = module_path!().split(':').next().unwrap();
  std::path::Path::new(crate_name).join(file_path)
  }};
 }