tslint to eslint migration

[jrieken]

This PR explores to migrate our custom tslint rules to eslint rules and adopts eslint in general.

Rules that we have today and that need migration

• duplicateImportsRule.ts (comes with eslint)
• importPatternsRule.ts (this PR)
• layeringRule.ts (9819da6)
• noDomGlobalsRule.ts (moved to custom solution)
• noNewBufferRule.ts (eslint rule, 291ee00)
• noNlsInStandaloneEditorRule.ts (2ea9132)
• noNodejsGlobalsRule.ts (moved to custom solution)
• noStandaloneEditorRule.ts (b05b481)
• noUnexternalizedStringsRule.ts (a61f38e)
• translationRemindRule.ts (a3bd604)

Other work packages that are required to migrate away from eslint

• investigate using https://eslint.org/docs/rules/no-restricted-imports (our needs are too special)
• find estree-equivalent of import foo = require('...')
• use ruledir-setting instead of plugin-approach?
• migrate our existing tslint-config to eslint (using tslint-to-eslint-config result plus tweaks)
• integrate into build
• integrate into precommit hook
• editor integration using our extension

[Stanzilla]

Just curious, what's the reason behind the move?

[mattacosta]

@Stanzilla The TSLint project is winding down and will no longer be maintained in the future. See palantir/tslint#4534.

[bpasero]

Pushed 7909462 to move the globals rules (node.js, DOM) into a custom solution that uses the TS API directly. I could not get that to work with a pure tsconfig.json solution, mainly because the options are not fine grained enough to exclude certain DOM types.

Btw there is a eslint rule for "new Buffer": https://github.com/eslint/eslint/blob/master/lib/rules/no-buffer-constructor.js

[jrieken]

@bpasero Won't this rule help you? https://eslint.org/docs/rules/no-restricted-globals.

[jrieken]

current rule mapping/migration state (tslint <=> eslint)

👌 class-name <=> @typescript-eslint/class-name-casing
👌 curly <=> curly
👌 duplicate-imports <=> no-duplicate-imports
👌 import-patterns <=> code-import-patterns
👌 label-position <=> no-unused-labels (similar)
👌 layering <=> code-layering
👌 no-arg <=> no-caller
👌 no-construct <=> no-new-wrappers
👌 no-debugger <=> no-debugger
👌 no-duplicate-super <=> constructor-super
👌 no-duplicate-switch-case <=> no-duplicate-case
👌 no-eval <=> no-eval
👌 no-new-buffer <=> no-buffer-constructor
👌 no-nls-in-standalone-editor <=> code-no-nls-in-standalone-editor
👌 no-sparse-arrays <=> no-sparse-arrays
👌 no-standalone-editor <=> code-no-standalone-editor
👌 no-string-throw <=> no-throw-literal
👌 no-unexternalized-strings <=> code-no-unexternalized-strings
👌 no-unsafe-finally <=> no-unsafe-finally
👌 no-var-keyword <=> no-var
👌 semicolon <=> @typescript-eslint/semi
👌 translation-remind <=> code-translation-remind
👌 triple-equals <=> eqeqeq
👌 no-redundant-jsdoc <=> jsdoc/no-types (only TS-files, no JS)

---

• ✋ 👌no-duplicate-variable <=> no-redeclare
  OFF, fails on enum Foo; namespace Foo;BUT only useful when using var-keyword - which we have disabled via no-var-keyword. let and const are checked by the compiler/runtime and therefore OK to be ignored.
• ✋ 👌 no-unused-expression <=> no-unused-expressions
  Added custom fork which supports OptionalCallExpression(also see Optional Chaining and Nullish coalescing Operator arrived at Stage 4 eslint/eslint#12642)
• ✋ 🙅‍♂ no-for-in-array <=> @typescript-eslint/no-for-in-array
  OFF, needs type info. Can be done with some additional effort but I'd say not worth the effort
• ✋ 🙅‍♂ number-literal-format <=> N/A
  Rule does not exist in eslint, but would be easy to add a custom rule, check that numbers are 0.1 not .1 and 10 not 00010. I leave that for later...
• ✋ 🙅‍♂ no-restricted-globals <=> no-restricted-globals
  Configured but not known as tslint-rule, so we never really had this rule and @bpasero also added a custom solution for this.

[jrieken]

fyi @sandy081

[sandy081]

Good catch by the linter

[jrieken]

fyi @mjbvz

[bpasero]

I think no-restricted-globals is still valid to have (and not covered by my solution), since it exists in ESLint, I can bring it back.