defmt issue when crate name starts with number

[jessetp]

defmt does not work when the crate name starts with a number (e.g. 01_hello_extended.rs). I used the app template generator as suggested in the Knurling-session-20q4.

Dependencies used in Cargo.toml:

[dependencies]
nrf52840-hal = "0.15.1"
embedded-hal = "0.2.7"
cortex-m = "0.7.6"
cortex-m-rt = "0.7.1"
defmt = "0.3.2"
defmt-rtt = "0.3.2"
panic-probe = { version = "0.3.0", features = ["print-defmt"] }
nb = "1.0.0"
crc_all = "0.2.2"

[Urhengulas]

Hi @jessetp, what error message are you getting?

[jessetp]

error: `03_temperature` is not a valid identifier
  --> src/bin/01_temperature_03.rs:32:5
   |
32 |     defmt::info!("{=f32} °C", temperature);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `defmt::info` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `co2-app` due to previous error

@Urhengulas
Renaming the file to start with an alphabetic character fixes the error.

[Urhengulas]

Thank you. Can you please also share the whole example code?

[jessetp]

@Urhengulas , I've attached the zipped project, minus the target folder (for size limits).

co2-app.zip

[Urhengulas]

I am able to reproduce your issue by renaming src/bin/temperature_03.rs to src/bin/01_temperature_03.rs and running it:

$ # download and extract zip
$ cd co2-app/

$ cargo run --bin temperature_03
<this suceeds>

$ mv src/bin/temperature_03.rs src/bin/01_temperature_03.rs
$ cargo run --bin 01_temperature_03
error: `01_temperature_03` is not a valid identifier
  --> src/bin/01_temperature_03.rs:32:5
   |
32 |     defmt::info!("{=f32} °C", temperature);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in the macro `defmt::info` (in Nightly builds, run with -Z macro-backtrace for more info)

I am tried to run cargo expand but this doesn't give more info atm and notably also doesn't include the expanded defmt::info call:

$ DEFMT_LOG=info cargo expand --bin 01_temperature_03

#![feature(prelude_import)]
#![no_main]
#![no_std]
#[prelude_import]
use core::prelude::rust_2018::*;
#[macro_use]
extern crate core;
#[macro_use]
extern crate compiler_builtins;
use co2_app as _;
use embedded_hal::blocking::delay::DelayMs;
use nrf52840_hal::{self as hal, Temp, Timer};
#[doc(hidden)]
#[export_name = "main"]
pub unsafe extern "C" fn __cortex_m_rt_main_trampoline() {
    __cortex_m_rt_main()
}
fn __cortex_m_rt_main() -> ! {
    let board = hal::pac::Peripherals::take().unwrap();
    let mut timer = Timer::new(board.TIMER0);
    let mut temp = Temp::new(board.TEMP);
    loop {
        let temperature: f32 = temp.measure().to_num();
        timer.delay_ms(2000_u32);
    }
}

I also tried to run it with -Z macro-backtrace as the error message suggests, but couldn't get that to run, despite running it on nightly.

Will continue later.

[Urhengulas]

The error ...

• does not occur with defmt::println!, but all the log-level-macros
• also occurs when there is no variable passed to the macro

  #![no_main]
  #![no_std]
  
  use krate as _; // global logger + panicking-behavior + memory layout
  
  #[cortex_m_rt::entry]
  fn main() -> ! {
      defmt::info!("Hello, world!");
  
      krate::exit()
  }

• occurs no matter what is passed to DEFMT_LOG
• originates from: https://github.com/knurling-rs/defmt/blob/16d7f0d56f509963f6dae43219a27f048c619511/macros/src/function_like/log/env_filter/parse.rs#L101

[Urhengulas]

I tried one approach to fixing this, which is just ignoring leading numbers: https://github.com/knurling-rs/defmt/tree/accept-crate-names-with-leading-numbers

It works for bin names like 123_hello.rs, 123hello.rs, but not 123.rs, which (surprising to me) is a valid bin name.