Standalone binary

[mo8it]

Here is a proof of concept for #1919 of how the file embedding would be done with some macro magic 🪄

You can take a look at the macro expansion generated by cargo-expand:

Macro expansion

static EMBEDDED_FILES: EmbeddedFiles = EmbeddedFiles {
    info_toml_content: "...",
    exercises_dir: ExercisesDir {
        readme: EmbeddedFile {
            path: "exercises/README.md",
            content: b"...",
        },
        files: &[
            EmbeddedFile {
                path: "exercises/quiz1.rs",
                content: b"...",
            },
            EmbeddedFile {
                path: "exercises/quiz2.rs",
                content: b"...",
            },
            EmbeddedFile {
                path: "exercises/quiz3.rs",
                content: b"...",
            },
        ],
        dirs: &[
            EmbeddedFlatDir {
                path: "exercises/00_intro",
                readme: EmbeddedFile {
                    path: "exercises/00_intro/README.md",
                    content: b"...",
                },
                content: &[
                    EmbeddedFile {
                        path: "exercises/00_intro/intro1.rs",
                        content: b"...",
                    },
                    EmbeddedFile {
                        path: "exercises/00_intro/intro2.rs",
                        content: b"...",
                    },
                ],
            },
            ...
        ],
    },
};

Now that we have this static instance of the type EmbeddedFiles, we can implement further logic on this type and use the instance anywhere in the code :D

[mo8it]

The proof of concept is now done! Ignore the failing tests and the missing polish, again. It is still a draft. I want @shadows-withal's approval before finishing this :)

How to try it out

1. Run cargo install --path . in this git branch.
2. Go into some temporary directory.
3. Run rustlings and notice the hint about initialization.
4. Run rustlings init
5. A directory with the name rustlings will be created
6. The exercises directory will be dumped from the binary into the rustlings directory and the rust-project.json Cargo.toml file will be automatically generated.
7. Run cd rustlings to go into the generated directory
8. Now test the commands watch, list, run, verify, reset and hint and do some exercises. Everything should work.
9. Note that reset now dumps the exercise file from the binary. There is no git repository. The user can optionally initialize a repo like with any project.

[mo8it]

I discarded the rust-project.json file. rustlings now automatically generates a Cargo.toml file on initialization. This file contains a [[bin]] entry for every exercise!

This should make things much smoother and less hacky, especially because we have many issues related to the language server.

This should also enable us to use Cargo instead of rustc to run the exercises. That would especially make Clippy exercises less of a trouble. This approach also allows us to easily add dependencies to the exercises in case we want to do so in the future.