Add descriptions and examples to each lint rule

[bartlomieju]

All lint rules should be updated to contains some kind of method that returns description as well as some examples of valid and invalid. This feature will be used to generate documentation.

• adjacent-overload-signatures
• ban-ts-comment
• ban-types
• ban-untagged-ignore
• ban-untagged-todo
• constructor-super
• default-param-last
• eqeqeq
• explicit-function-return-type
• explicit-module-boundary-types
• for-direction
• getter-return
• no-array-constructor
• no-async-promise-executor
• no-await-in-loop
• no-case-declarations
• no-class-assign
• no-compare-neg-zero
• no-cond-assign
• no-const-assign
• no-constant-condition
• no-control-regex
• no-debugger
• no-delete-var
• no-dupe-args
• no-dupe-class-members
• no-dupe-else-if
• no-dupe-keys
• no-duplicate-case
• no-empty
• no-empty-character-class
• no-empty-interface
• no-empty-pattern
• no-eval
• no-ex-assign
• no-explicit-any
• no-extra-boolean-cast
• no-extra-non-null-assertion
• no-extra-semi
• no-fallthrough
• no-func-assign
• no-global-assign
• no-import-assign
• no-inferrable-types
• no-inner-declarations
• no-invalid-regexp
• no-irregular-whitespace
• no-misused-new
• no-mixed-spaces-and-tabs
• no-namespace
• no-new-symbol
• no-non-null-asserted-optional-chain
• no-non-null-assertion
• no-obj-calls
• no-octal
• no-prototype-builtins
• no-redeclare
• no-regex-spaces
• no-self-assign
• no-setter-return
• no-shadow-restricted-names
• no-sparse-arrays
• no-this-alias
• no-this-before-super
• no-throw-literal
• no-undef
• no-unreachable
• no-unsafe-finally
• no-unsafe-negation
• no-unused-labels
• no-unused-vars
• no-var
• no-with
• prefer-as-const
• prefer-const
• prefer-namespace-keyword
• require-yield
• single-var-declarator
• triple-slash-reference
• use-isnan
• valid-typeof

[bartlomieju]

I think it's high time to start adding rules documentation so I'm pinning this issue.

So to support basic documentation and website generation we need to change LintRule trait minimally:

pub trait LintRule {
  fn new() -> Box<Self>
  where
    Self: Sized;
  fn lint_module(
    &self,
    context: Arc<Context>,
    module: &swc_ecmascript::ast::Module,
  );
  fn code(&self) -> &'static str;
  fn docs(&self) -> &'static str; // <--- new method
}

LintRule::docs() would return a string with written documentation. I think it makes sense to support markdown being returned from this function because we could print it out nicely to terminal (for example using termimad) as well as auto-generate website similar to doc.deno.land.

Documentation for each lint rule should contain a short synopsis on what the rule does, why is it used and examples of both valid and invalid code.

Example for ban-untagged-todo:

Each "TODO" comment should be tagged with either a username or issue number.

Untagged TODOs often lead to confusion on the original intent of the TODO, 
especially after several git changes.

**Valid:**
// TODO(#101): need to handle edge case for n = 0
function foo(n: number) {
  // ...
}

**Invalid:**
// TODO: need to handle edge case for n = 0
function foo(n: number) {
  // ...
}

CC @lucacasonato

[DomParfitt]

I'm happy to look at implementing this on the rules I've implemented once the trait is updated. From a quick scan that covers:

• no-empty
• no-cond-assign
• valid-typeof
• no-unsafe-finally
• no-compare-neg-zero
• no-dupe-keys

🙂

[bartlomieju]

@DomParfitt great, thank you! I've already merged #343