why do we need to preface terminal commands with yarn?

[bensacc]

this is a very general question, but I'm a bit confused about the relationship between yarn and hardhat. I get that we use yarn to install all of the packages (I think...), but why do we subsequently need to reference yarn in terminal commands like:

yarn hardhat ....

I use pip to install python packages for example, but I don't subsequently use:

pip python...

to run python code. why can I not just use "hardhat" the way I'd use "python" in the terminal, if that makes sense?

[PatrickAlphaC]

Great question!

So python, javascript, node, pip, and yarn all do different things. Python by default installs things in the global sense, but javascript installs things in the local sense.

Why you can "just run" python packages

When I do pip install packageX I can often just run packageX right in the terminal.

Let's say for example you install solc-select with pip install solc-select. If you run which solc-select you'll see that the package is located at someplace like /Library/Frameworks/Python.framework/Versions/3.9/bin/solc-select (it might be different for you), but this location is where all your python packages get installed. (the which command tells use where a package is located).

However, when I run yarn add packageX I still have to run yarn packageX.

Let's say for example you install hardhat with yarn add hardhat. If you run which hardhat you won't get a response, but you'll see a package.json, yarn.lock, and a node_modules folder in the folder that you ran yarn add hardhat to. In the node_modules folder, you'll see a ton of folders, and one of them is hardhat. So instead of installing it globally, we installed it locally to the folder that we are in.
Now you "can" install javascript (or more correctly, npm) packages globally, but some of them don't support this, hardhat is one of those that doesn't support being installed globally. However, the hardhat shorthand does support being installed globally, and you can run yarn global add hardhat-shorthand and then, you'll be able to run which hh (hh is the terminal command that gets installed from hardhat-shorthand) and you'll get something like /usr/local/bin/hh, and then you can run the command like hh --help.

Why you need to add yarn before javascript (npm) packages

So this explains why you can "just run" python packages (since they get installed in the global sense by default, and python doesn't really have a "local" sense), but doesn't explain why we need to have the yarn before our npm packages.

The yarn command actually acts as 2 functions:

• Package manager (like the pip command)
• Package executor (sort of like the python command)

If you've seen the keyword npm & npx, those are the same thing:

• npm is the package manager
• npx is the package executor
  And yarn is just the two of those combined.

The yarn and npx command act as package executors, so when we call yarn hardhat or npx hardhat it knows it's trying to execute the hardhat package, and will look in the node_modules folder to find that package and do what it has to do.

If we just run hardhat, there is no global binding in our terminal to tell our terminal what that means! So we have to prefix it with yarn and then let yarn handle it.

Hope that makes sense.

One more note, comparing python and js will make your head spin a little. For example, you can run python dostuff.py but you can't run javascript dostuff.js, you'd have to run node dostuff.js. Javascript is built for the browser, and nodejs is an engine that allows you to run javascript outside of the browser, like in a terminal.

[PatrickAlphaC]

TL;DR

Cuz javascript & python are hella different

[bensacc]

fantastic answer, thank you so much!!