[][src]Crate sfwtools

Design

In the spirit of Software Tools, the aim is to make components re-usable in three ways:

  1. Implement core features as functions, so they can be re-used within Rust. These functions should generally return a Result type, so the caller can decide how to deal with the error.
  2. Executable commands with a simple interface that typically act as thin wrappers around the library functions, or perhaps combine the library functions in interesting ways.
  3. As well designed code that can be copied as repurposed when necessary.

A fourth avenue may be explored, which is to adopt the nushell approach to transfering tabular data between commands.

For a related project that also follows Software Tools in Rust, and may serve as an interesting comparison, see Sweater.

Functional facilities

Higher-order-functions (HOFs) are frequently used to reduce code complexity, verbosity, and the risk of errors. Primary examples are map, for_each (like map but effectful), and fold. As pointed out in Software Tools, pp 21, "The best programs are designed in terms of loosely coupled functions that each does a simple task."

Currently Implemented Tools

  • [x] cp
  • [x] wc
  • [ ] detab

Dependencies

Since the goal is to make the software both as self-contained and as illustrative as possible, we've tried to rely on very few dependencies. The following exceptions exist:

  • fp-core This is what one would typically find as part the standard library in a functional language, so we have included it here. Though Rust is functional in a sense — it has lamda functions (i.e. Rust closures) and the stand library has many higher-order functions (HOFs) — its standard library doesn't include traits that are commonly found to be helpful abstracts in functional languages. We will use a few of these where it is particularly illustrative or sensible, but will stick with idiomatic Rust where that is obviously simpler.
  • seahorse Seahorse is a minimal argument parser. Judging by some results returned by Google, clap is far more popular, but has additional dependencies; we are striving for being as portable as possible, so the minimality seemed to line up with that goal. Additionally, Clap doesn't appear to allow passing in argument lists directly, which is useful for maintaining separate commands that build on each other. In any case, argument parsing is only used very late in the application logic, and most of the API could be used without worrying about it.

Currently unused

  • im Immutable data structures that implement structural sharing can be even more performant than std's mutable structures for large data types, and while Rust makes mutation far safer than most languages, mutation can still result in confusion at times, so in the cases where clarity is more important than performance (or performance doesn't matter much, e.g. one-ops), it may be preferable to use immutable data structures.

Build

Currently, do generate small builds the following commands are required.

  1. (only once per environment) Make source code for the standard library available:
rustup component add rust-src --toolchain nightly
cargo +nightly build -Z build-std --target x86_64-unknown-linux-gnu --release
  1. (optional) strip binary - see links in notes

Misc Notes

Using todo!() to

Using todo!() from std::todo is a helpful way to incrementally develop a feature while still getting feedback from the compiler. [TODO: show example]

A caveat is that currently you need code in the function after the todo!(), even if it doesn't match the type. For instance, we can use a function like:

pub fn some_num() -> i32 {
    todo!(); ();
}

Most beneficial is that rustc will warn you if you a todo!() is left in your code, since it would result in a panic if that execution path were to occur.

Optimizing for size

  • https://github.com/johnthagen/min-sized-rust

Project administration

Git hooks

Cargo-Husky

We use cargo-husky to keep in line; it enforces several checks with a pre-push hook. Sometimes it is a bit restrictive, so if we need to push in-progress work to a branch, we can use git push --no-verify -u origin feature_branch. Cargo-husky expects certain files to be at the root of the repository, thus the symlinks.

pre-commit

We include the following, less stringent checks for pre-commit.

#!/bin/sh

# Put in your Rust repository's .git/hooks/pre-commit to ensure you never
# breaks rustfmt.                                                                                                                      
#
# WARNING: rustfmt is a fast moving target so ensure you have the version that
#          all contributors have.

for FILE in `git diff --cached --name-only`; do
    if [[ -f "$FILE" ]] && [[ $FILE == *.rs ]] \
           && ! rustup run nightly rustfmt --unstable-features \
                --skip-children $FILE; then
        echo "Commit rejected due to invalid formatting of \"$FILE\" file."
        exit 1
    fi
done

cd Rust/sfw-tools && cargo readme > README.md && git add README.md

As can be seen this also gnerates the README from doc comments in lib.rs.

Re-exports

pub use bytes_iter::BytesIter;
pub use constants::*;
pub use error::*;
pub use util::*;
pub use copying::*;
pub use counting::*;

Modules

bytes_iter
constants
copying
counting
error
util

Functions

get_args
run_app

This is a wrapper around the Seahorse App.run that emits a nicer user error message if there are no aguments provided.