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In this video, we'll discuss working

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effectively with Cargo fmt and Cargo

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clippy. Cargo fmt is a really useful

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tool for Auto formatting your Rust code

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according to Rust style guidelines. If

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you get an error when you run Cargo

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fmt, then you need to install the Rust

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format component using Rust up, it looks

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like this.

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Rust fmt is most likely already

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installed so you probably won't have to

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run that step. Once its installed

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Cargo fmt will do its job, Cargo

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fmt is usually silent what it does is

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auto format your code. Let's go take a

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look here's our code, and it's already

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properly formatted, so let's mess it up a

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bit.

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Okay that's a bit of an odd way to

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format things, let's go and run Cargo

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fmt and see what happens.

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Now I'll go back to our code

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again and we'll see that Cargo fmt

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moved it back to the correct format. This is

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super useful to avoid arguments about

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where parens go, wear braces go, how you

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should format things. There's one

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suggested way to do it, there's one

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built-in tool to do it, if you just use

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it no one has to have any arguments,

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it's just however the tool does it, and

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it looks pretty good.

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Okay what about Cargo clippy? This might

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also already be installed on your system

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but if it isn't just run Rust up

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component add clippy, and Rust up will

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install it for you. While Cargo fmt

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deals with style,

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clippy is a collection of lints to catch

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common mistakes and help you improve

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your Rust code. Let's try it out

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let's start by looking at the second

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warning use of unwrapped or followed by

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a call to new. So the problem here is

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that string new will happen, whether or

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not the value is needed. So we're going

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to do an allocation and create a new

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string, whether or not we actually need

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the new string. So this is suggesting

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instead call unwrap or default, and then

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inside the method it will create a

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default for a string, which is a blank

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string only if it's needed.

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So that's an optimization, so let's go

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fix that.

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OK we've made the fix, let's go run

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Cargill clippy again.

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All right we fixed that item as we can

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see it doesn't show up anymore, let's

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look at the next one. Length comparison

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to zero so we're using dot Len to get a

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length, and we're comparing it to zero

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and we're told using naught is empty is

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clearer and more explicit. Okay

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so they want us to put a not in front,

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and use is empty instead of Len, so let's

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go make that change.

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Alright let's go around Cargo clippy

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again,

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great clippy couldn't find anything to

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complain about. I suggest using Cargo

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fmt and Cargo clippy, either in a

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continuous integration check, or put it

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in something like a Git pre-commit hook.

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I'll give an example of using this in a

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Git pre-commit hook. The file to create

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is dot Git hooks pre-commit.

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I'm going to paste in my preferred setup.

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This file will be interpreted as

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Shell code. This will make it so that

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before get makes a commit it will run

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Cargo fmt, and then let it do its

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thing and then it will run Cargo clippy

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and abort the commit if any warnings are

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present. The - D warnings turns the

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warnings into errors, which will cause

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the hook to fail. We can go see it in

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action if I go add a formatting problem

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and do something that will make clippy

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complain, but first let's save this,

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and let's make it executable.

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And now let's go at our changes.

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Here is a change that Cargo fmt will

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revert,

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and here's some code that clippy will

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complain about. Let's try to commit our

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code and see what happens.

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Okay so clippy complained about the

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linting error, what about Cargo fmt? If

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we go back we see Cargo fmt did its

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thing, so then we fix the linting error,

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and now when we try to commit it should

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work.

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In the next video, we'll talk about how

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to handle errors gracefully.