fix(publish): Move .crate out of final artifact location

When `target_dir == build_dir`, ensure `cargo publish` doesn't put
intermediate artifacts in the final artifact location of `cargo
package`.

If anyone was relying on this behavior of `cargo publish`, it will break
them.
We could avoid this and instead consider the location change to be part
of the opt-in of using `build-dir` (until we make it opt-out).
Note that we expect to be able to change the layouf of content written
to `build-dir` even if users aren't opting in.

On the other hand, this will help identify people relying on
intermediate artifacts.

While there aren't any performance benefits to this, it consolidates all
of the uplifting logic and avoids dealing with overlapping `target_dir`
and `build_dir`.
We could optimize this further by doing a `rename` and only doing a copy
if that fails.

Author: epage

src/cargo/ops/cargo_package/mod.rs

@@ -1,7 +1,7 @@
 use std::collections::BTreeMap;
 use std::collections::BTreeSet;
 use std::collections::HashMap;
-use std::fs::{self, File};
+use std::fs::File;
 use std::io::SeekFrom;
 use std::io::prelude::*;
 use std::path::{Path, PathBuf};
@@ -160,11 +160,8 @@ fn create_package(
     }
 
     let filename = pkg.package_id().tarball_name();
-    let dir = ws.build_dir().join("package");
-    let mut dst = {
-        let tmp = format!(".{}", filename);
-        dir.open_rw_exclusive_create(&tmp, gctx, "package scratch space")?
-    };
+    let dir = ws.build_dir().join("package").join("tmp-crate");
+    let dst = dir.open_rw_exclusive_create(&filename, gctx, "package scratch space")?;
 
     // Package up and test a temporary tarball and only move it to the final
     // location if it actually passes all our tests. Any previously existing
@@ -176,16 +173,10 @@ fn create_package(
     let uncompressed_size = tar(ws, opts, pkg, local_reg, ar_files, dst.file(), &filename)
         .context("failed to prepare local package for uploading")?;
 
-    dst.seek(SeekFrom::Start(0))?;
-    let src_path = dst.path();
-    let dst_path = dst.parent().join(&filename);
-    fs::rename(&src_path, &dst_path)
-        .context("failed to move temporary tarball into final location")?;
-
     let dst_metadata = dst
         .file()
         .metadata()
-        .with_context(|| format!("could not learn metadata for: `{}`", dst_path.display()))?;
+        .with_context(|| format!("could not learn metadata for: `{}`", dst.path().display()))?;
     let compressed_size = dst_metadata.len();
 
     let uncompressed = HumanBytes(uncompressed_size);
@@ -219,22 +210,22 @@ pub fn package(ws: &Workspace<'_>, opts: &PackageOpts<'_>) -> CargoResult<Vec<Fi
 
     let packaged = do_package(ws, opts, pkgs)?;
 
+    // Uplifting artifacts
     let mut result = Vec::new();
-    let target_dir = ws.target_dir();
-    let build_dir = ws.build_dir();
-    if target_dir == build_dir {
-        result.extend(packaged.into_iter().map(|(_, _, src)| src));
-    } else {
-        // Uplifting artifacts
-        let artifact_dir = target_dir.join("package");
-        for (pkg, _, src) in packaged {
-            let filename = pkg.package_id().tarball_name();
-            let dst =
-                artifact_dir.open_rw_exclusive_create(filename, ws.gctx(), "uplifted package")?;
-            src.file().seek(SeekFrom::Start(0))?;
-            std::io::copy(&mut src.file(), &mut dst.file())?;
-            result.push(dst);
-        }
+    let artifact_dir = ws.target_dir().join("package");
+    for (pkg, _, src) in packaged {
+        let filename = pkg.package_id().tarball_name();
+
+        let tmp = format!(".{filename}");
+        let dst = artifact_dir.open_rw_exclusive_create(tmp, ws.gctx(), "uplifted package")?;
+        src.file().seek(SeekFrom::Start(0))?;
+        std::io::copy(&mut src.file(), &mut dst.file())?;
+
+        let src_path = dst.path();
+        let dst_path = artifact_dir.join(&filename).into_path_unlocked();
+        std::fs::rename(src_path, dst_path)?;
+
+        result.push(dst);
     }
 
     Ok(result)