warn on unused variables

[strager]

• [ ] #1075

[strager]

Configuration idea:

"warn-if-unused": true

// don't warn for let, params, functions, classes, types, ...
"warn-if-unused": ["import", "const"]

"warn-if-unused": {
  "/[^_].*/": true,    // warn on any variable without a _ prefix
  "/^.*/": ["import"]  // warn on all unused imported variables
}

Concern: What if multiple regexp patterns match? Concern: Should we try to be compatible with ESLint?

[strager]

Alternative config idea:

"warn-if-unused": true

// don't warn for let, params, functions, classes, types, ...
"warn-if-unused": ["import", "const"]

"warn-if-unused": [
  "import",                               // warn on all unused imported variables
  {"/[^_].*/": ["const", "let", "var"]},  // warn on any local var without a _ prefix
  "/^[A-Z].*/"                            // warn on anything unused starting with a capital letter
]

Array items are processed in order. If no array item matches, don't warn.

But how would we say "warn for unused anything except unused classes"?

Another idea (probably bad):

"warn-if-unused": [
  "import",                               // warn on all unused imported variables
  ["/[^_].*/", ["const", "let", "var"]],  // warn on any local var without a _ prefix
  "/^[A-Z].*/"                            // warn on anything unused starting with a capital letter
]

Outer-most array is 'or', but middle arrays are 'and', and inner-most arrays are 'or'.

Verbose style:

"warn-if-unused": [
  "import",
  {"name": "/[^_].*/", "kind": ["const", "let", "var"], "warn": true},
  "/^[A-Z].*/"
]

I think I like the verbose style for clarity.

[vegerot]

jooc would

const {a} = require('foo')

be an import or const type?

[strager]

const