Implement `cargo new --script` by tomassedovic · Pull Request #17627 · rust-lang/cargo

tomassedovic · 2026-10-23T13:49:44Z

What does this PR try to resolve?

This adds a new --script flag to the unstable script feature (the flag is behind the same feature flag).

With it, cargo new --script script.rs will create a script.rs file with the following contents:

#!/usr/bin/env -S cargo +nightly -Zscript
---
package.edition = "2024"
[dependencies]
---
fn main() {
    println!("Hello, world!");
}

This makes it a little easier to create cargo scripts. By specifying the edition, the script will run with no warning and provide basic front matter scaffolding.

Notes to reviewers

Partially implements: #16849

This is related to the cargo script stabilisation effort (project goal: rust-lang/goals#119), but not a blocker.

It aims to improve the end-user experience for creating new scripts -- especially depending on how exactly will the edition discussion be resolved (rust-lang/rust#152254).

I fixed the obvious CI failures, but haven't added new tests nor fixed the UI ones yet.

At this point, it's a proof-of-concept for a feature that's not been accepted yet (cargo#16849). I'd love to hear from the maintainers whether it's worth doing this now/ever (I use use cargo script and wished this existed).

If so, I'm happy to work out the final shape and push it forward.

🤖 LLM involvement: no LLM/AI was (knowingly) used anywhere in the process of working on this feature.

This will create a new "cargo script" file. It's a single file ending with `.rs` which can be run with `cargo <file>`. The contents of the file are a hello world example as well as a front matter manifest that includes the current edition and an empty `dependencies` section.

It doesn't make sense for `cargo init`.

Previously, we generated: ``` [package] edition = "2024" ``` which is needlessly verbose compared to the new: ``` package.edition = "2024" ```

rustbot · 2026-10-23T13:49:55Z

r? @Muscraft

rustbot has assigned @Muscraft.
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Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: @Muscraft, @epage, @weihanglo
@Muscraft, @epage, @weihanglo expanded to Muscraft, epage, weihanglo
Random selection from Muscraft, epage, weihanglo

tomassedovic · 2026-10-23T13:50:51Z

        )
        .arg_new_opts()
+        // NOTE: add the flag here instead of `arg_new_opts`, because it makes no sense for `cargo init`
+        // TODO: show the flag in `cargo help new`


I haven't figured out how to make this show in help yet. Waiting to see if this work is even desirable (now) before figuring that out.

I'll be grateful for pointers of course.

View changes since the review

tomassedovic · 2026-10-23T13:52:57Z

-            (_, false) => NewProjectKind::Bin,
+        let kind = match (bin, lib, script) {
+            (true, true, _) | (_, true, true) | (true, _, true) => {
+                anyhow::bail!("must specify exactly one of: lib, bin or script outputs")


This function is called from both cargo new and cargo init, but --script makes no sense in cargo init (I think).

So this error message will be appropriate in cargo new, but less so in cargo init.

Do we want to print a different error in either case?

View changes since the review

tomassedovic · 2026-10-23T13:54:46Z

    let cfg = gctx.get::<CargoNewConfig>(["cargo-new"])?;

+    // TODO: cleaner way to detect it's a script? E.g. by passing the `kind` to `MkOptions`?
+    let is_script = name.ends_with(".rs") && opts.source_files.is_empty();


Do we want to support creating files that don't end with .rs (or any extension)?

The likely use case would be "regular" unix scripts relying on the executable permission and shebang.

View changes since the review

tomassedovic · 2026-10-23T13:55:29Z

        None => Edition::LATEST_STABLE.to_string(),
    };
-    manifest["package"]["edition"] = toml_edit::value(edition);
+    manifest["package"]["edition"] = toml_edit::value(&edition);


Note, this is to prevent an error saying edition was moved here.

View changes since the review

tomassedovic · 2026-10-23T13:59:15Z

+    if is_script {
+        let default_script_content = format!(
+            "\
+#!/usr/bin/env -S cargo +nightly -Zscript


This shebang targets rustup-installed cargo. It wouldn't work with cargo installed as an OS package or user-compiled cargo.

I'm assuming that while the feature is unstable, most nightly users use rustup so this is the right default before stabilisation.

What do you think?

View changes since the review

tomassedovic · 2026-10-23T14:00:00Z

+            "\
+#!/usr/bin/env -S cargo +nightly -Zscript
+---
+package.edition = \"{}\"


I opted for the shorter syntax (instead of specifying the [package] table.

Happy to change that if desirable.

View changes since the review

tomassedovic · 2026-10-23T14:01:10Z

+#!/usr/bin/env -S cargo +nightly -Zscript
+---
+package.edition = \"{}\"
+[dependencies]


This also differs from what the issue proposes, but I think it's more convenient for the end-user.

It (a) shows that dependencies can be specified and (b) makes it easier to do so at the cost of an extra line.

View changes since the review

tomassedovic · 2026-10-23T14:03:59Z

I don't want to override a reviewer just yet, but @epage should be at least aware, given his involvement in cargo script.

epage · 2026-10-23T14:31:21Z

At this point, it's a proof-of-concept for a feature that's not been accepted yet (cargo#16849). I'd love to hear from the maintainers whether it's worth doing this now/ever (I use use cargo script and wished this existed).

Note that that is a conversation for the Issue.

tomassedovic · 2026-10-26T15:31:27Z

Thank you, I posted the comments there.

tomassedovic added 6 commits October 22, 2026 09:46

Put the --script flag behind the script unstable feature

97dcaeb

Move the --script flag to cargo new

0f873b0

It doesn't make sense for `cargo init`.

Remove todo comment that's no longer needed

2e9697e

Fix a failing test

cb10d22

Use oneline package.edition syntax for the default script frontmatter

043e451

Previously, we generated: ``` [package] edition = "2024" ``` which is needlessly verbose compared to the new: ``` package.edition = "2024" ```

rustbot added A-cli Area: Command-line interface, option parsing, etc. Command-new S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 23, 2026

rustbot assigned Muscraft Oct 23, 2026

tomassedovic commented Oct 23, 2026

View reviewed changes

tomassedovic marked this pull request as draft October 23, 2026 14:04

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 23, 2026

tomassedovic mentioned this pull request Oct 23, 2026

cargo new --script #16849

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Implement `cargo new --script` - #17627

Implement `cargo new --script`#17627
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What does this PR try to resolve?

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