Misleading error message when crates.io is replace-with a local source

[hoodmane]

Problem

When using a local source via a replace-with in config.toml and there is a missing package, cargo build gives confusing errors saying that it searched crates-io for the package when it only looked in the local file system. The error it gives is identical to the error from an actually missing package:

error: no matching package named `<package name>` found
location searched: registry `crates-io`
required by package `example v0.1.0`

Possible Solution(s)

If you run cargo seach it gives much more specific information:

$ cargo search ahash
error: crates-io is replaced with non-remote-registry source dir /.../cargo-bug/vendor;
include `--registry crates-io` to use crates.io

It would be great if the original error included this "crates-io is replaced with non-remote-registry source" remark.

Steps

1. Unpack this zip archive: cargo-bug.zip
2. Run cargo build in root
3. Get error:

   error: no matching package named `ahasha` found
   location searched: registry `crates-io`
   required by package `example v0.1.0 (/home/rchatham/Documents/programming/tmp/cargo-bug)`
   

As an alternative, instead of unpacking, make an empty folder, cd into it, make the following files and then do the following shell instructions:

Cargo.toml

[package]
name = "example"
version = "0.1.0"
edition = "2021"

[dependencies]
ahash = { version = "^0.8.9" }

.cargo/config.toml

[source.crates-io]
replace-with = "vendored-sources"

[source.vendored-sources]
directory = "vendor"

Shell instructions

Then:

mkdir src
touch src/lib.rs
mkdir vendor
cargo build

Version

cargo 1.84.0-nightly (15fbd2f 2024-10-08)
release: 1.84.0-nightly
commit-hash: 15fbd2f
commit-date: 2024-10-08
host: x86_64-unknown-linux-gnu
libgit2: 1.8.1 (sys:0.19.0 vendored)
libcurl: 8.9.0-DEV (sys:0.4.74+curl-8.9.0 vendored ssl:OpenSSL/1.1.1w)
ssl: OpenSSL 1.1.1w 11 Sep 2023
os: Ubuntu 22.4.0 (jammy) [64-bit]

[weihanglo]

Thanks for the report.

It might be improved by using a similar mechanism you pointed out. The relevant code cargo-search handling error resides here and here.

We might want a simpler message for resolver errors, such as

error: no matching package named `ahash` found
location searched: registry `crates-io` (replaced with registry `/path/to/vendor`)
required by package `example v0.1.0 (/home/rchatham/Documents/programming/tmp/cargo-bug)`

Calling SourceId::display_registry_name should give a good enough descriptive name of the source I believe.

[chentodd]

Hi,

I did some research on the issue the used Registry::describe_source in resolver/errors to get replacement message, and it showed following messages when building cargo-bug.zip:

error:` no matching package named `ahasha` found
location searched: registry `crates-io`, directory source `/home/todd/Desktop/cargo-bug/vendor` (which is replacing registry `crates-io`)
required by package `example v0.1.0 (/home/todd/Desktop/cargo-bug)`

Since I'm new to both open source and Rust, I'm not sure if this is the right way to approach the issue, and I would greatly appreciate any feedback.

Thanks.

[weihanglo]

Feel free to claim this issue and submit a pull request!

Personally I lean toward keeping the message concise, and prefer showing the replaced source first. Other may have different preference.

[chentodd]

@rustbot claim

[weihanglo]

I did some research on the issue the used Registry::describe_source in resolver/errors to get replacement message, and it showed following messages when building cargo-bug.zip:

error:` no matching package named `ahasha` found
location searched: registry `crates-io`, directory source `/home/todd/Desktop/cargo-bug/vendor` (which is replacing registry `crates-io`)
required by package `example v0.1.0 (/home/todd/Desktop/cargo-bug)`

I just understood what you meant. We already have such a message, so probably we can just apply this a simple fix, and update all test snapshots.

diff --git a/src/cargo/core/resolver/errors.rs b/src/cargo/core/resolver/errors.rs
index 7fbf4e22c0e..64503b9401a 100644
--- a/src/cargo/core/resolver/errors.rs
+++ b/src/cargo/core/resolver/errors.rs
@@ -355,3 +355,6 @@ pub(super) fn activation_error(
         }
-        msg.push_str(&format!("location searched: {}\n", dep.source_id()));
+        msg.push_str(&format!(
+            "location searched {}\n",
+            registry.describe_source(dep.source_id())
+        ));
         msg.push_str("required by ");

[chentodd]

Thanks, I'll follow the advice!