Can't find extern crate

[duartebranco01]

Describe the bug

Hello, I'm having an error when the Rust code generated by the optimizer builder can't import extern crate:

 --> C:\Users\User\.cargo\registry\src\index.crates.io-6f17d22bba15001f\optimization_engine-0.9.0\src\constraints\affine_space.rs:3:1
  |
3 | extern crate modcholesky;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error[E0463]: can't find crate for ndarray
 --> C:\Users\User\.cargo\registry\src\index.crates.io-6f17d22bba15001f\optimization_engine-0.9.0\src\constraints\affine_space.rs:4:1
  |
4 | extern crate ndarray;
  | ^^^^^^^^^^^^^^^^^^^^^ can't find crate

error[E0433]: failed to resolve: use of undeclared crate or module roots
  --> C:\Users\User\.cargo\registry\src\index.crates.io-6f17d22bba15001f\optimization_engine-0.9.0\src\constraints\epigraph_squared_norm.rs:53:32
   |
53 |         let cubic_poly_roots = roots::find_roots_cubic(a3, a2, a1, a0);
   |                                ^^^^^ use of undeclared crate or module roots

These crates exist in the index.crates.io-6f17d22bba15001f folder.

Do I need to configure some kind of path variable or use specific versions of something?

To Reproduce

Steps to reproduce the behavior:

Run the builder (with the versions of programs indicated bellow):

builder = og.builder.OpEnOptimizerBuilder(problem, meta, build_cfg, solver_cfg)
builder.build()

Expected behavior

No problem importing extern crate.

System information:

⚠️ Please, provide the following information:

• System/Platform: PC
• OS: Windows 10
• rustup version: 1.27.1
• rustc version: 1.78.0
• cargo version: 1.78.0
• Python version: 3.9.13

Additional context

Builder params:

problem = og.builder.Problem(u, p, sum_squared_error) \
    .with_penalty_constraints(penalty_constraints) \
    .with_constraints(u_bounds)

build_cfg = og.config.BuildConfiguration() \
    .with_build_directory("build") \
    .with_tcp_interface_config() \
    .with_build_c_bindings()

meta = og.config.OptimizerMeta() \
    .with_optimizer_name("my_optimizer")

solver_cfg=og.config.SolverConfiguration()\
    .with_tolerance(1e-5)\
    .with_delta_tolerance(1e-4)\
    .with_initial_penalty(1e3)

builder = og.builder.OpEnOptimizerBuilder(problem, meta, build_cfg, solver_cfg)

builder.build()

[alphaville]

I've never encountered something like this on Linux or MacOS. The code also works on Google Colab.

@ruairimoran have you seen anything similar on Windows?

@duartebranco01 a possible explanation can be that you're trying to run the code on a machine without an Internet connection, so cargo fails to download the dependencies.

[alphaville]

It seems that this error is only likely to happen if the machine on which you're compiling is not connected to the Internet. When we need to use OpEn on a robot or vehicle, I would first compile on my laptop, test the code in simulations, then move it to the robot and compile there with cargo build.

Let me know if this resolves the issue.

[alphaville]

Fixed in #355