Add a newline after metadata when initializing scripts with other metadata blocks

[merlinz01]

Summary

uv doesn't separate the metadata block from other blocks when adding the script block to a script, which results in the next block being considered part of the script block and causes errors when running.

See #12499 for more details.

Closes #12499

Test Plan

I manually tested the most common scenario, but there's a few edge cases that would be good to have tests for.

I would have written the tests also, but I was running into errors like this:

$ cargo test --package uv-scripts
   Compiling uv-configuration v0.0.1 (/home/merlin/Projects/uv/crates/uv-configuration)
error: cannot find attribute `value` in this scope
 --> crates/uv-configuration/src/project_build_backend.rs:8:38
  |
8 |     #[cfg_attr(feature = "schemars", value(hide = true))]
  |                                      ^^^^^

error: could not compile `uv-configuration` (lib) due to 1 previous error

[charliermarsh]

Thanks, a few tests would be great. You can apply this patch:

diff --git a/crates/uv-configuration/src/project_build_backend.rs b/crates/uv-configuration/src/project_build_backend.rs
index fb1a171e9..90fac2ec9 100644
--- a/crates/uv-configuration/src/project_build_backend.rs
+++ b/crates/uv-configuration/src/project_build_backend.rs
@@ -5,7 +5,7 @@
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub enum ProjectBuildBackend {
     #[cfg_attr(feature = "clap", value(hide = true))]
-    #[cfg_attr(feature = "schemars", value(hide = true))]
+    #[cfg_attr(feature = "schemars", schemars(skip))]
     /// Use uv as the project build backend.
     Uv,
     #[default]

[charliermarsh]

Ah, looks like you also need #12504.

[merlinz01]

Hmm, now I'm getting lots of errors like this:

$ cargo test --package uv-scripts
   Compiling uv-settings v0.0.1 (/home/merlin/Projects/uv/crates/uv-settings)
error[E0277]: the trait bound `PythonPreference: ValueEnum` is not satisfied
   --> crates/uv-settings/src/settings.rs:252:35
    |
252 |     pub python_preference: Option<PythonPreference>,
    |                                   ^^^^^^^^^^^^^^^^ the trait `ValueEnum` is not implemented for `PythonPreference`
    |
    = help: the trait `ValueEnum` is implemented for `clap::ColorChoice`
# 25 more similar errors...

This is what I'm running:

$ cargo --version
cargo 1.85.1 (d73d2caf9 2024-12-31)
$ rustup --version
rustup 1.26.0 (2024-04-01)
info: This is the version for the rustup toolchain manager, not the rustc compiler.
info: The currently active `rustc` version is `rustc 1.85.1 (4eb161250 2025-03-15)`
$ rustc --version
rustc 1.85.1 (4eb161250 2025-03-15)
$ uname -a
Linux myhostname 6.8.0-55-generic #57-Ubuntu SMP PREEMPT_DYNAMIC Wed Feb 12 23:42:21 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
$ cat /etc/os-release 
NAME="Linux Mint"
VERSION="22.1 (Xia)"

[charliermarsh]

Those PRs should merge shortly, then you can rebase on top of them if you'd like. (The problem, I think, is that we tend to run cargo test over the entire workspace, so as long as one crate enables the necessary features, all crates have access. Thus, you only see these failures if you try to test a crate individually.)

[merlinz01]

Thanks for the speedy fix! I have added tests.

[charliermarsh]

It might be easier to do this via snapshot testing?

[merlinz01]

I can't find how to import the uv_snapshot macro.

[charliermarsh]

I looked into it briefly but I think insta strips some whitespace, and these tests are intentionally quite whitespace-sensitive, so lets leave it as-is.

[charliermarsh]

Thanks.