Merge pull request #229 from quantified-uncertainty/contributing-april-update

Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -52,3 +52,78 @@ See [here](https://github.com/NixOS/nixpkgs/issues/107375)
 # Pull request protocol
 
 Please work against `staging` branch. **Do not** work against `master`. Please do not merge without approval from some subset of Quinn, Sam, and Ozzie; they will be auto-pinged. 
+
+# Code Quality
+- Aim for at least 8/10* quality in ``/packages/squiggle-lang``, and 7/10 quality in ``/packages/components``. 
+- If you submit a PR that is under a 7, for some reason, describe the reasoning for this in the PR.
+
+* This quality score is subjective.
+
+# Rescript Style
+
+**Use `->` instead of `|>`**  
+Note: Our codebase used to use `|>`, so there's a lot of that in the system. We'll gradually change it.
+
+**Use `x -> y -> z` instead of `let foo = y(x); let bar = z(foo)`**
+
+**Don't use anonymous functions with over three lines**  
+Bad:
+```rescript
+  foo
+  -> E.O.fmap(r => {
+    let a = 34;
+    let b = 35;
+    let c = 48;
+    r + a + b + c
+  }
+```
+Good:
+```rescript
+  let addingFn = (r => {
+    let a = 34;
+    let b = 35;
+    let c = 48;
+    r + a + b + c
+  }
+  foo -> addingFn
+```
+
+**Write out types for everything, even if there's an interface file**  
+We'll try this for one month (ending May 5, 2022), then revisit.
+
+**Use the Rescript optional default syntax**  
+Rescript is clever about function inputs. There's custom syntax for default and optional arguments. In the cases where this applies, use it.
+
+From https://rescript-lang.org/docs/manual/latest/function:
+```rescript
+// radius can be omitted
+let drawCircle = (~color, ~radius=?, ()) => {
+  setColor(color)
+  switch radius {
+  | None => startAt(1, 1)
+  | Some(r_) => startAt(r_, r_)
+  }
+}
+```
+
+**Use named arguments**  
+If a function is called externally (in a different file), and has either:
+1. Two arguments of the same type
+2. Three paramaters or more.
+
+**Module naming: Use x_y as module names**  
+For example: ``Myname_Myproject_Add.res``. Rescript/Ocaml both require files to have unique names, so long names are needed to keep different parts separate from each other.
+
+See [this page](https://dev.to/yawaramin/a-modular-ocaml-project-structure-1ikd) for more information. (Though note that they use two underscores, and we do one. We might refactor that later.
+
+**Module naming: Don't rename modules**
+We have some of this in the Reducer code, but generally discourage it. 
+
+**Use interface files (.resi) for files with very public interfaces**
+
+### Recommended Rescript resources  
+- https://dev.to/yawaramin/a-modular-ocaml-project-structure-1ikd 
+- https://github.com/avohq/reasonml-code-style-guide 
+- https://cs.brown.edu/courses/cs017/content/docs/reasonml-style.pdf
+- https://github.com/ostera/reason-design-patterns/ 
+