Can't Scaffold A New Project With Name Beginning With Number?

[JimLynchCodes]

Problem
Problem is that cargo gives an error "error: Package names starting with a digit cannot be used as a crate name" rather than creating a project with name beginning with number.

Steps

run this:

cargo new 1-hello-world

Possible Solution(s)

Notes

There is the additional output in the console, "use --name to override crate name", but I'm not really sure how to change my command to make it work. 🤔

Output of cargo version: cargo 1.42.0 (8633429 2020-01-31)

[hbina]

I am not sure I understand this issue. cargo simply does not allow crates to have names starting with a digit. This is a reasonable restriction imo.

In particular, here's the exact code that checks against this

cargo/src/cargo/util/restricted_names.rs

Lines 45 to 57 in ab32ee8

	pub fn validate_package_name(name: &str, what: &str, help: &str) -> CargoResult<()> {
	let mut chars = name.chars();
	if let Some(ch) = chars.next() {
	if ch.is_digit(10) {
	// A specific error for a potentially common case.
	bail!(
	"the name `{}` cannot be used as a {}, \
	the name cannot start with a digit{}",
	name,
	what,
	help
	);
	}

Or did I misunderstood you?

[JimLynchCodes]

@hbina "This is a reasonable restriction imo."

To me is seems like a completely unnecessary restriction. Folder names beginning with numbers are perfectly valid, and in this case I do want to create a folder name that begins with a number (mostly because these folders represent chapters, and I want them to be ordered automatically by the file system).

Can we remove this digit check altogether? I don't see what purpose or benefit it serves.

[Eh2406]

This works if you want the folder to start with a number:
cargo new 1-hello-world --name hello-world
or
cargo new hello-world && mv hello-world 1-hello-world
The fact that the name field in Cargo.toml can not start with a digit is connected to the fact that in Rust identifiers can not start with a digit. That would be hard to change.

Now, I'd be excited for a PR that improved the error message to something like:

> cargo new 1-hello-world
error: Package names starting with a digit cannot be used as a crate name
did you mean "cargo new 1-hello-world --name hello-world"?

I don't know how hard that would be.

[JimLynchCodes]

Thanks for the explanation @Eh2406 🙏

I agree that your proposed error message would be a nicer UX.

[lofiguy]

I know that it's been a long time @JimLynchCodes. However maybe someone encounter this problem again so the solution is:

$ cargo new hello-world

And you can simply change the directory's name:

$ mv hello-world/ 1-hello-world/

And after that operation if you go to project dir:

$ cd 1-hello-world/

You can simply run the project without any problems:

┌─(~/dev/rust//0-hello-world)
└─(12:01:55 on master ✭)──> cargo run                                                                                                                                                                                                                                  ──(Sun,Jun26)─┘
   Compiling hello-world v0.1.0 (/home/ax/dev/rust/book-1.58/by-example/0-hello-world)
    Finished dev [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/hello-world
Hello, world!

Important:

You shouldn't change the name field in Cargo.toml for 1-hello-world. The file should looks like this:

[package]
name = "hello-world"
version = "0.1.0"
edition = "2021"

[Anynomouss]

@lofiguy Is your answer not unnecessary long and complex?
The simple answer is that you can specify a project folder with a number, but not a crate name with a number using the cargo --name option:

cargo new 1-hello-world --name hello-world

The above code will create a folder 1-hello-world with a crate with the name hello-world

The code in the directory 1-hello-world can be run like any project using cargo run