Scaling
Best practices With Syntax Trees
Will Klein
Best Practices
Four Years Ago
Two Years Ago
Today
Testing
User
Experience
Developer
Experience
Documentation
Code review
Convention Tests
Convention Tests, AKA
- Linters
- Code analyzers
- Static analysis
Language
Conventions
What about our project Conventions?
What If We could write our own convention tests?
Convention Test "Frameworks"
- Common tests included
- Pluggable testing API
- ESLint, for example
// Life, Universe, and Everything
var answer = 6 * 7;// Life, Universe, and Everything
var answer = 6 * 7;10111010001011011101000101
...
How does this work?
// Life, Universe, and Everything
var answer = 6 * 7;[var] [answer] [=] [6] [*] [7][;]...
Tokenize
// Life, Universe, and Everything
var answer = 6 * 7;[var] [answer] [=] [6] [*] [7][;]...
...
?
Parse
A Syntax Tree
Syntax Tree
- Abstract syntax tree
- AST
- Syntax tree is easier to say
An example
This Code...
should really be
no-unused-vars
semi
ESLint Rules
???
ESLint Rules
IfStatement
Nested IfStatement
Nested IfStatement
ESLint
- Builds our syntax tree for us
- Iterates over nodes in the tree
- For each node, do we have a test?
ESLint: Rule boilerplate
ESLint: Rule boilerplate
ESLint: Rule boilerplate
ESLint: Rule boilerplate
Nested IfStatement
ESLint: context
Directly nested CASE
Directly nested CASE
Directly nested CASE
Directly nested CASE
block Nested CASE
block Nested CASE
block Nested CASE
Siblings Case
Else If Case
Else If Case
Else If Case
no-nested-if
Demo
Docs & Code
What else?
We Just Learned
- Convention tests
- Syntax trees
- How to write a convention test using syntax trees
Go Forth and Test
- Implement existing tools
- Consider your project's conventions
- Write your own convention tests
Go Forth and Test
- Implement existing tools
- Consider your project's conventions
- Write your own convention tests
- Improve your developer experience
programs must be written for people to read, and only incidentally for machines to execute
Donald Knuth
Structure and Interpretation of Computer Programs
http://willkle.in
will.klein@gmail.com
Thanks
@willslab