no-shadowed-variable: issue with interface extension

[sinedied]

Bug Report

• TSLint version: 5.5.0
• TypeScript version: 2.4.2
• Running TSLint via: angular-cli

TypeScript code being linted

import { RequestOptionsArgs } from '@angular/http';

export enum HttpCachePolicy {
  Never = <any>false,
  Always = <any>true,
  Update = <any>'update'
}

// RequestOptionArgs is declared in a re-exported module, so we have to extend the original module to make it work
// properly (see  https://github.com/Microsoft/TypeScript/issues/13897)
declare module '@angular/http/src/interfaces' {

  // Use this interface to extend requests options if needed
  export interface RequestOptionsArgs {
    cache?: boolean|HttpCachePolicy;
    skipErrorHandler?: boolean;
  }

}

with tslint.json configuration:

{
  "rulesDirectory": [
    "node_modules/codelyzer"
  ],
  "rules": {
    "arrow-return-shorthand": true,
    "callable-types": true,
    "class-name": true,
    "comment-format": [
      true,
      "check-space"
    ],
    "curly": true,
    "eofline": true,
    "forin": true,
    "import-blacklist": [
      true,
      "rxjs"
    ],
    "import-spacing": true,
    "indent": [
      true,
      "spaces"
    ],
    "interface-over-type-literal": true,
    "jsdoc-format": true,
    "label-position": true,
    "max-line-length": [
      true,
      120
    ],
    "member-access": false,
    "member-ordering": [
      true,
      "public-before-private",
      "static-before-instance",
      "variables-before-functions"
    ],
    "no-arg": true,
    "no-bitwise": true,
    "no-console": [
      true,
      "debug",
      "info",
      "time",
      "timeEnd",
      "trace"
    ],
    "no-construct": true,
    "no-debugger": true,
    "no-duplicate-variable": [
      true,
      "check-parameters"
    ],
    "no-duplicate-super": true,
    "no-empty": false,
    "no-empty-interface": true,
    "no-eval": true,
    "no-inferrable-types": [
      true,
      "ignore-params"
    ],
    "no-shadowed-variable": true,
    "no-string-literal": false,
    "no-string-throw": true,
    "no-switch-case-fall-through": true,
    "no-trailing-whitespace": true,
    "no-unnecessary-initializer": true,
    "no-unused-expression": true,
    "no-use-before-declare": true,
    "no-var-keyword": true,
    "object-literal-sort-keys": false,
    "one-line": [
      true,
      "check-open-brace",
      "check-catch",
      "check-else",
      "check-whitespace"
    ],
    "prefer-const": true,
    "quotemark": [
      true,
      "single"
    ],
    "radix": true,
    "semicolon": [
      "always"
    ],
    "triple-equals": [
      true,
      "allow-null-check"
    ],
    "typedef": [
      true,
      "parameter",
      "property-declaration"
    ],
    "typedef-whitespace": [
      true,
      {
        "call-signature": "nospace",
        "index-signature": "nospace",
        "parameter": "nospace",
        "property-declaration": "nospace",
        "variable-declaration": "nospace"
      }
    ],
    "typeof-compare": true,
    "unified-signatures": true,
    "variable-name": false,
    "whitespace": [
      true,
      "check-branch",
      "check-decl",
      "check-operator",
      "check-separator",
      "check-type"
    ],
    "directive-selector": [
      true,
      "attribute",
      "app",
      "camelCase"
    ],
    "component-selector": [
      true,
      "element",
      "app",
      "kebab-case"
    ],
    "use-input-property-decorator": true,
    "use-output-property-decorator": true,
    "use-host-property-decorator": true,
    "no-input-rename": true,
    "no-output-rename": true,
    "use-life-cycle-interface": true,
    "use-pipe-transform-interface": true,
    "component-class-suffix": true,
    "directive-class-suffix": true,
    "no-access-missing-member": true,
    "templates-use-public": true,
    "invoke-injectable": true
  }
}

Actual behavior

This error is reported:

ERROR: /Users/noda/github/generator-ngx-app/sample/src/app/core/http/request-options-args.ts[20, 20]: Shadowed name: 'RequestOptionsArgs'

Expected behavior

No error should be reported here as the intent is to extend the existing interface, this is not a case of shadowed variable.

[adidahiya]

I guess you're right, but why do you need to import RequestOptionsArgs in that file? It looks unused (would be flagged by tsc --noUnusedLocals).

[sinedied]

This is maybe a TypeScript issue, but if I remove the import the interface extension does not work well, maybe because it depends of the load order. Maybe it's fixed in latest TypeScript versions, I'll make some tests.

Anyway the TS compiler does not flag it as unused.

[adidahiya]

Ok, thanks for the response. We'd accept a PR that makes the rule ignore shadowed types inside ambient declaration blocks (declare module ...).