CODEWITHSUNDEEP
ruststructopt
womble
womble

Reputation: 12426

structopt unable to find its Args parser when defined in a separate file

I'm starting on a command-line tool in Rust, and hitting a wall right from the get-go. I can parse command-line arguments using StructOpt if the Opt struct is defined in main.rs, but since I want to be able to pass the Opt struct into the library code, I'm defining it in its own file so that other parts of the library know what it's all about.

Here's the version of the code that's dumping the fewest errors, although I concede that it's largely cobbled together by trying things suggested by the compiler and some random SO suggestions, so it may be completely wrong.

The build error I'm getting is:

$ cargo run
   Compiling basic v0.1.0 (/home/mpalmer/src/action-validator/blobble)
error[E0433]: failed to resolve: maybe a missing crate `structopt`?
 --> src/opt.rs:8:5
  |
8 |     /// Activate debug mode
  |     ^^^^^^^^^^^^^^^^^^^^^^^ not found in `structopt::clap`
  |
help: consider importing this struct
  |
3 | use opt::structopt::clap::Arg;
  |

For more information about this error, try `rustc --explain E0433`.
error: could not compile `basic` due to previous error
$ cargo --version
cargo 1.56.0 (4ed5d137b 2021-10-04)
$ rustc --version
rustc 1.56.0 (09c42c458 2021-10-18)

(Yes, I have tried adding use opt::structopt::clap::Arg;, just in case, but the error doesn't go away and I get a warning about an unused import -- while still being told to try adding the same use that is unused, which is amusing)

Cargo.toml

[package]
name = "basic"
version = "0.1.0"
authors = ["User"]

[dependencies]
structopt = "0.3"

src/main.rs

extern crate basic;
extern crate structopt;

use basic::Opt;
use structopt::StructOpt;

fn main() {
    let opt = Opt::from_args();
    println!("{:#?}", opt)
}

src/lib.rs

mod opt;

pub use crate::opt::Opt;

src/opt.ts

extern crate structopt;

use self::structopt::StructOpt;

#[derive(StructOpt, Debug)]
#[structopt(name = "basic")]
pub struct Opt {
    /// Activate debug mode
    #[structopt(short,long)]
    debug: bool,
}

Suggestions gratefully appreciated.

Upvotes: 1

Views: 398

Answers (1)

Zeppi
Zeppi

Reputation: 1245

A working version is

Cargo.toml

[package]
name = "basic"
version = "0.1.0"
authors = ["User"]
edition = "2018"

[dependencies]
structopt = "0.3"

lib.rs

#[macro_use] extern crate structopt;
use structopt::StructOpt;

pub mod opt;

opt.rs

#[derive(StructOpt, Debug)]
#[structopt(name = "basic")]
pub struct Opt {
    /// Activate debug mode
    #[structopt(short,long)]
    debug: bool,
}

main.rs

#[macro_use] extern crate structopt;
use structopt::StructOpt;

fn main() {
    let opt = basic::opt::Opt::from_args();
    println!("{:#?}", opt);
}

You need to declare use structopt::StructOpt because from_args trait must be in the scope.

Upvotes: 2

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