Crate greplab 

98-008: Intro to the Rust Programming Language

Grep Lab

The goal of this homework is to make sure you know how to create a command line tool in Rust, as well as how to write unit tests for your programs.

This homework is going to be very different from other homeworks. There is no autograder, and we will be manually grading your submission for not just correctness but also code quality and robustness through a code review.

For this homework, you will follow Chapter 12 of the Rust Book and create a project called minigrep. Follow the hyperlink and go through all of Chapter 12, building minigrep as you go along.

There will be no handout for this homework. Instead, run cargo new minigrep in your terminal to get started!

We encourage you to not skim through the book and blindly copy and paste any code you see. On top of asking you to write robust code, we will require one “extra” thing from your submission, which will check if you actually understand what you are pasting into your submission.

Requirements

You must add at least 1 additional feature to minigrep on top of the functionality described in the Book. Given this requirement, it will be more efficient for you to read the (relatively short) Chapter 12 in its entirety, rather than copy and paste everything and then reverse engineer. See the Extra Features section below for some potential features you could add. You must document this feature as a documentation comment (we will run cargo doc on your submission when we grade it, so it the documentation should be in the root of your library crate).

Another soft requirement is that you add unit tests. This won’t count towards the first 100 points, but will definitely contribute a non-significant amount to your code review score. We care more about quality over quantity, but you should have at least 2 types of test cases (general functionality, edge cases, potentially even performance benchmarking if you want to go above and beyond with criterion).

Extra Features

The extra feature you want to add is up to you once you’ve finished the base minigrep.

• A very basic feature that you could add is a “count” flag through -c or --count, which changes the output to show how many lines a pattern is in, rather than printing out all of the lines.
• Another feature you could implement is searching directories as well as specific files.
• You can add regex support by using the regex crate.
• You can integrate a third-party CLI library such as clap to make the command line interface more user-friendly.
• You can integrate a third-party error-handling library such as anyhow or thiserror into your error handling code.

If you would like to do this with a different third-party crate, please ask us for permission first!

There are many things that you could do here, so try and be creative if you have time! A good source of inspiration would be the man page for grep. If you have more than one additional feature, we will probably give you extra credit points in your code review.

Whatever you choose, make sure you document it by indicating what your feature is in your documentation comments. The very first thing we will do when grading your submission will be running cargo doc --open, so make sure it is obvious!

You should also make an effort to include a help message in your binary (triggered by -h or --help flags). Make sure to include a description of each flag and its behavior. The help message should also be printed if the user gives invalid command line arguments.

Code Review and Grading

Your submission will be manually graded, and we will give you a code review. If you simply follow along the tutorial and add a simple additional feature, you will get a full 100 points on this assignment. The code review will give you up to 100 extra credit points.

We are mainly looking at the correctness of your feature (does your feature work how you describe in your documentation and does it run without modifications), the robustness of your code (architecture and design), the quality of tests you add, and general style (documentation and comments).

If you simply follow along the tutorial and add a simple additional feature, you will not score very well on the code review. A high-quality submission should look very different from the code presented in the tutorial.

The way we grade this assignment will be different from almost every Computer Science course here at CMU, where grading is mainly based on an autograder, and maybe a handful of points deductions for style. Instead, we will be looking at your code wholistically, judging it based on how people expect you to write code outside of school.

However, we understand that this is still a StuCo, which is why this is all for extra credit. Nevertheless, we still believe that this is an important exercise to go through as you will likely need to go through this process in the future.

We are going to be really harsh! This practice is taken from CMU’s Operating Systems course, 15-410/605. Please don’t worry if you receive a low code review score, and remember that this is all extra credit!

Submission

This time, you will submit the entire minigrep crate to Gradescope (instead of just the src/ directory)!

Please do not include the target/ subdirectory when you zip the crate’s root folder, either manually or with cargo clean. You can always regenerate it with cargo build and cargo test.

Make sure that your code is fully formatted and linted with the following commands:

cargo clippy && cargo fmt --all -- --check

By following Rust’s style guidelines, you ensure that anybody reading your code (who is familiar with Rust) will be able to easily navigate your code. This can help with diving into an unfamiliar code base, and it also eliminates the need for debate with others over style rules, saving time and energy.

See the official guidelines for more information.

Collaboration

In general, feel free to discuss homeworks with other students! As long as you do not copy someone else’s work, any communication is fair game.

All formal questions should be asked on Piazza. Try to discuss on Piazza so that other students can see your questions and answers as well!

You can also discuss on Discord, but try to keep any technical questions on Piazza.

Feedback

We would like to reiterate that you should let us know if you spent anywhere in significant excess of an hour on this homework.

In addition, Rust has a notoriously steep learning curve, so if you find yourself not understanding the concepts, you should reach out to us and let us know as well — chances are, you’re not the only one!