cargo-new: `workspace` is added as an inline table

[weihanglo]

Problem

In #12779, cargo adds new packages to [workspace.members] automatically. This is great when workspace.member array alreay exists, but the format doesn't look good when workspace array is missing.

Steps

1. cargo new foo && cd foo
2. cargo add bar --lib

And you'll get the resulting TOML

workspace = { members = ["bar"] }
[package]
name = "foo"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

Possible Solution(s)

Don't add the new package to workspace.members if there is no existing workspace in Cargo.toml.

Notes

No response

Version

cargo 1.77.0-nightly (1ae631085 2024-01-17)
release: 1.77.0-nightly
commit-hash: 1ae631085f01c1a72d05df1ec81f3759a8360042
commit-date: 2024-01-17

[epage]

... is the error instead that we shouldn't be doing this if foo doesn't have a [workspace] at all?

If the existing toml contains an empty inline workspace table like workspace = {}, should we reformat it to [workspace]?

So far, we've taken the approach of preserving what the user already has rather than cleaning it up. That is rustfmt's job.

[weihanglo]

... is the error instead that we shouldn't be doing this if foo doesn't have a [workspace] at all?

This sounds better 👍🏾.

[linyihai]

@rustbot claim

I'll try.