Rust: run sample .fsx via cargo-script (?)

[jkone27]

Description

trying to run a sample .fsx and have it executed by cargo script but i get some errors,
maybe we should have a way to keep/compile also comments, so that cargo script can still read comments in the output?

i have checked this: https://github.com/alfonsogarciacaro/fable-rust-sample/blob/main/Cargo.toml, not clear though how to do it with cargo script if possible..

Repro code

dotnet new tool-manifest
dotnet tool install fable --prerelease
touch test.fsx
dotnet fable test.fsx --lang rust
cargo install cargo-script
cargo script test.fs.rs // seems to fail for missing deps
cargo script -D cargo_fable test.fs.rs // fails as no loop or expr provided...

Expected and actual results

we are able to execute some F# code as Rust code

Related information

• Fable version: dotnet fable --version : 4.1.4
• Operating system: Mac OS

[ncave]

@jkone27 Unfortunately comments are not available in the Fable AST.

We could add a Fable.Core.Rust helper to emit Rust comments in the future.

Perhaps using a cargo-script template can work, something like this:

//! ```cargo
//! [dependencies]
//! fable_library_rust = { path = "./fable_modules/fable-library-rust" }
//! ```
#![allow(unused_imports)]
#{prelude}
extern crate fable_library_rust;
#{script}

(although I wasn't able to make templates work, but perhaps I'm not doing something right).

Anyway, it's all about the dependency on fable_library_rust, so if you find a way to provide that dependency, it should work.

Personally I don't see much difference between using cargo-script vs. just putting your .fsx script in a /src folder and having a simple Cargo.toml (like the one you linked to above) to define the dependencies, therefore skipping the need for cargo-script to generate the package. But that's obviously up to you.

[jkone27]

cannot find that lib on crates.io, is it still there?

Updating crates.io index
error: no matching package named `fable_library_rust` found

[jkone27]

was trying to follow the sample here, but then had to modify toml to include a different bin,

[package]
name = "fable-rust-sample"
version = "0.1.0"
edition = "2021"

[[bin]]
name = "testRust"
path = "testRust.rs"

[dependencies]
fable_library_rust = { path = "./fable_modules/fable-library-rust" }

and eventually ended up with this build error ..

.> cargo run --manifest-path /Users/admin/Repositories/scripts/test_fable_rust/Cargo.toml
Watching .
   Compiling core-foundation-sys v0.8.4
   Compiling cfg-if v1.0.0
   Compiling libc v0.2.146
   Compiling num-traits v0.2.15
   Compiling memchr v2.5.0
   Compiling regex-syntax v0.7.2
   Compiling arrayvec v0.7.3
   Compiling iana-time-zone v0.1.57
   Compiling time v0.1.45
   Compiling getrandom v0.2.10
   Compiling aho-corasick v1.0.2
   Compiling uuid v1.3.4
   Compiling num-integer v0.1.45
   Compiling rust_decimal v1.29.1
   Compiling chrono v0.4.26
   Compiling num-bigint v0.4.3
error: couldn't read /Users/admin/Repositories/scripts/test_fable_rust/target/debug/build/num-bigint-27dce587fe4d8a0f/out/radix_bases.rs: No such file or directory (os error 2)
   --> /Users/admin/.cargo/registry/src/github.com-1ecc6299db9ec823/num-bigint-0.4.3/src/biguint/convert.rs:759:9
    |
759 |         include! { concat!(env!("OUT_DIR"), "/radix_bases.rs") }
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: this error originates in the macro `include` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not compile `num-bigint` due to previous error

[jkone27]

is it related to this one? rust-num/num-bigint#218.

[ncave]

@jkone27 Could be, not sure. I haven't encountered it cause I usually run stable.

It might have been fixed in the master branch, but the last num-bigint release is from 2021, so we might have to reference it from github.

I just tried rustc 1.72.0-nightly, seems to compile fine, are you running something else?

[jkone27]

i will update my rustc, i have : rustc 1.69.0 (84c898d65 2023-04-16)

[jkone27]

same error with latest stable from rustup (1.70)...

admin@LT-NLAMS-3108 ~ % rustc --version
rustc 1.70.0 (90c541806 2023-05-31)

ok sorry it worked after cargo clean and cargo run, but not when using fable clean and fable run commands...

i get error only when running via (error above with this script sequence) as in the fable rust test project

dotnet fable --lang rs -e rs --watch --runScript

this gives that error, but if i simply compile with fable to rust, and run instead

cargo clean
cargo run myscript.fsx

then it works fine!

[ncave]

@jkone27 Yes, --watch and --runScript flags are mostly for targeting JavaScript where there is no subsequent compilation step after Fable is done. Same thing for clean, it only cleans Fable-produced files, not build artifacts of compilations that happen after that.

I'm glad it works, feel free to close this, or rename to a more specific issue if you have one.
Thanks for testing and providing feedback!