Add linting

.eslintignore

@@ -0,0 +1,3 @@
+dist/
+lib/
+node_modules/

.eslintrc.json

@@ -0,0 +1,55 @@
+{
+    "plugins": ["jest", "@typescript-eslint"],
+    "extends": ["plugin:github/es6"],
+    "parser": "@typescript-eslint/parser",
+    "parserOptions": {
+      "ecmaVersion": 9,
+      "sourceType": "module",
+      "project": "./tsconfig.json"
+    },
+    "rules": {
+      "eslint-comments/no-use": "off",
+      "import/no-namespace": "off",
+      "no-unused-vars": "off",
+      "@typescript-eslint/no-unused-vars": "error",
+      "@typescript-eslint/explicit-member-accessibility": ["error", {"accessibility": "no-public"}],
+      "@typescript-eslint/no-require-imports": "error",
+      "@typescript-eslint/array-type": "error",
+      "@typescript-eslint/await-thenable": "error",
+      "@typescript-eslint/ban-ts-ignore": "error",
+      "camelcase": "off",
+      "@typescript-eslint/class-name-casing": "error",
+      "@typescript-eslint/func-call-spacing": ["error", "never"],
+      "@typescript-eslint/generic-type-naming": ["error", "^[A-Z][A-Za-z]*$"],
+      "@typescript-eslint/no-array-constructor": "error",
+      "@typescript-eslint/no-empty-interface": "error",
+      "@typescript-eslint/no-explicit-any": "error",
+      "@typescript-eslint/no-extraneous-class": "error",
+      "@typescript-eslint/no-for-in-array": "error",
+      "@typescript-eslint/no-inferrable-types": "error",
+      "@typescript-eslint/no-misused-new": "error",
+      "@typescript-eslint/no-namespace": "error",
+      "@typescript-eslint/no-non-null-assertion": "warn",
+      "@typescript-eslint/no-object-literal-type-assertion": "error",
+      "@typescript-eslint/no-unnecessary-qualifier": "error",
+      "@typescript-eslint/no-unnecessary-type-assertion": "error",
+      "@typescript-eslint/no-useless-constructor": "error",
+      "@typescript-eslint/no-var-requires": "error",
+      "@typescript-eslint/prefer-for-of": "warn",
+      "@typescript-eslint/prefer-function-type": "warn",
+      "@typescript-eslint/prefer-includes": "error",
+      "@typescript-eslint/prefer-interface": "error",
+      "@typescript-eslint/prefer-string-starts-ends-with": "error",
+      "@typescript-eslint/promise-function-async": "error",
+      "@typescript-eslint/require-array-sort-compare": "error",
+      "@typescript-eslint/restrict-plus-operands": "error",
+      "semi": "off",
+      "@typescript-eslint/type-annotation-spacing": "error",
+      "@typescript-eslint/unbound-method": "error"
+    },
+    "env": {
+      "node": true,
+      "es6": true,
+      "jest/globals": true
+    }
+  }

src/main.ts

@@ -1,11 +1,11 @@
 import * as core from '@actions/core';
 import * as github from '@actions/github';
-import { Octokit } from '@octokit/rest';
+import {Octokit} from '@octokit/rest';
 
-type Issue = Octokit.IssuesListForRepoResponseItem
-type IssueLabel = Octokit.IssuesListForRepoResponseItemLabelsItem
+type Issue = Octokit.IssuesListForRepoResponseItem;
+type IssueLabel = Octokit.IssuesListForRepoResponseItemLabelsItem;
 
-type Args = {
+interface Args {
   repoToken: string;
   staleIssueMessage: string;
   stalePrMessage: string;
@@ -17,9 +17,9 @@ type Args = {
   exemptPrLabel: string;
   onlyLabels: string;
   operationsPerRun: number;
-};
+}
 
-async function run() {
+async function run(): Promise<void> {
   try {
     const args = getAndValidateArgs();
 
@@ -43,7 +43,7 @@ async function processIssues(
     state: 'open',
     labels: args.onlyLabels,
     per_page: 100,
-    page: page
+    page
   });
 
   operationsLeft -= 1;
@@ -52,23 +52,26 @@ async function processIssues(
     return operationsLeft;
   }
 
-  for (var issue of issues.data.values()) {
+  for (const issue of issues.data.values()) {
     core.debug(`found issue: ${issue.title} last updated ${issue.updated_at}`);
-    let isPr = !!issue.pull_request;
+    const isPr = !!issue.pull_request;
 
-    let staleMessage = isPr ? args.stalePrMessage : args.staleIssueMessage;
+    const staleMessage = isPr ? args.stalePrMessage : args.staleIssueMessage;
     if (!staleMessage) {
       core.debug(`skipping ${isPr ? 'pr' : 'issue'} due to empty message`);
       continue;
     }
 
-    let staleLabel = isPr ? args.stalePrLabel : args.staleIssueLabel;
-    let exemptLabel = isPr ? args.exemptPrLabel : args.exemptIssueLabel;
+    const staleLabel = isPr ? args.stalePrLabel : args.staleIssueLabel;
+    const exemptLabel = isPr ? args.exemptPrLabel : args.exemptIssueLabel;
 
     if (exemptLabel && isLabeled(issue, exemptLabel)) {
       continue;
     } else if (isLabeled(issue, staleLabel)) {
-      if (args.daysBeforeClose >= 0 && wasLastUpdatedBefore(issue, args.daysBeforeClose)) {
+      if (
+        args.daysBeforeClose >= 0 &&
+        wasLastUpdatedBefore(issue, args.daysBeforeClose)
+      ) {
         operationsLeft -= await closeIssue(client, issue);
       } else {
         continue;
@@ -167,7 +170,7 @@ function getAndValidateArgs(): Args {
     )
   };
 
-  for (var numberInput of [
+  for (const numberInput of [
     'days-before-stale',
     'days-before-close',
     'operations-per-run'