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Prioritize target libs when there's multiple candidates #14650

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Prioritize target libs when there's multiple candidates #14650

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65 changes: 41 additions & 24 deletions src/librustc/metadata/loader.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -347,11 +347,11 @@ impl<'a> Context<'a> {
// read the metadata from it if `*slot` is `None`. If the metadata couldn't
// be read, it is assumed that the file isn't a valid rust library (no
// errors are emitted).
//
// If there are multiple candidates, and one of them lives in the target
// lib path, pick that candidate instead of erroring out.
fn extract_one(&mut self, m: HashSet<Path>, flavor: &str,
slot: &mut Option<MetadataBlob>) -> Option<Path> {
let mut ret = None::<Path>;
let mut error = 0;

if slot.is_some() {
// FIXME(#10786): for an optimization, we only read one of the
// library's metadata sections. In theory we should
Expand All @@ -364,6 +364,8 @@ impl<'a> Context<'a> {
}
}

let mut candidates: Vec<(Path, MetadataBlob)> = Vec::new();

for lib in m.move_iter() {
info!("{} reading metadata from: {}", flavor, lib.display());
let metadata = match get_metadata_section(self.os, &lib) {
Expand All @@ -380,30 +382,45 @@ impl<'a> Context<'a> {
continue
}
};
if ret.is_some() {
candidates.push((lib, metadata));
}
let (lib, metadata) = if candidates.len() > 1 {
info!("multiple {} candidates for `{}`", flavor, self.crate_id.name);
// look for one from the target lib path
let target_lib_path = self.filesearch.get_lib_path();

let (idx_opt, has_multiple) = {
let mut idxs = candidates.iter().enumerate().filter_map(|(i,&(ref lib, _))| {
if target_lib_path.is_ancestor_of(lib) { Some(i) } else { None }
});
(idxs.next(), idxs.next().is_some())
};
if idx_opt.is_some() && !has_multiple {
// only one library is in the target lib path
let idx = idx_opt.unwrap();
let (lib, metadata) = candidates.move_iter().nth(idx).unwrap();
info!("found candidate in target lib path: {}", lib.display());
(lib, metadata)
} else {
// either multiple libraries were found in the target lib path, or none
self.sess.span_err(self.span,
format!("multiple {} candidates for `{}` \
found",
flavor,
self.crate_id.name).as_slice());
self.sess.span_note(self.span,
format!(r"candidate \#1: {}",
ret.get_ref()
.display()).as_slice());
error = 1;
ret = None;
format!("multiple {} candidates for `{}` found",
flavor, self.crate_id.name).as_slice());
for (i, (lib, _)) in candidates.move_iter().enumerate() {
self.sess.span_note(self.span,
format!(r"candidate \#{}: {}", i+1,
lib.display()).as_slice());
}
return None;
}
if error > 0 {
error += 1;
self.sess.span_note(self.span,
format!(r"candidate \#{}: {}", error,
lib.display()).as_slice());
continue
} else {
match candidates.move_iter().next() {
Some(x) => x,
None => return None
}
*slot = Some(metadata);
ret = Some(lib);
}
return if error > 0 {None} else {ret}
};
*slot = Some(metadata);
Some(lib)
}

fn crate_matches(&mut self, crate_data: &[u8], libpath: &Path) -> bool {
Expand Down