add eslint, just "copy" from next.js repo

.eslintignore

@@ -0,0 +1,4 @@
+node_modules
+**/.next/**
+**/_next/**
+**/dist/**

.eslintrc.json

@@ -0,0 +1,227 @@
+{
+  "root": true,
+  "parser": "babel-eslint",
+  "plugins": ["react", "react-hooks"],
+  "env": {
+    "browser": true,
+    "commonjs": true,
+    "es6": true,
+    "node": true
+  },
+  "parserOptions": {
+    "ecmaVersion": 2018,
+    "sourceType": "module",
+    "ecmaFeatures": {
+      "jsx": true
+    }
+  },
+  "settings": {
+    "react": {
+      "version": "detect"
+    }
+  },
+  "overrides": [
+    { "files": ["**/__tests__/**"], "env": { "jest": true } },
+    {
+      "files": ["**/*.ts", "**/*.tsx"],
+      "parser": "@typescript-eslint/parser",
+      "parserOptions": {
+        "ecmaVersion": 2018,
+        "sourceType": "module",
+        "ecmaFeatures": {
+          "jsx": true
+        },
+        "warnOnUnsupportedTypeScriptVersion": false
+      },
+      "plugins": ["@typescript-eslint"],
+      "rules": {
+        // Already handled by TS
+        "no-dupe-class-members": "off",
+        "no-undef": "off",
+
+        // Add TypeScript specific rules (and turn off ESLint equivalents)
+        "@typescript-eslint/consistent-type-assertions": "warn",
+        "no-array-constructor": "off",
+        "@typescript-eslint/no-array-constructor": "warn",
+        "@typescript-eslint/no-namespace": "error",
+        "no-use-before-define": "off",
+        "@typescript-eslint/no-use-before-define": [
+          "warn",
+          {
+            "functions": false,
+            "classes": false,
+            "variables": false,
+            "typedefs": false
+          }
+        ],
+        "no-unused-vars": "off",
+        "@typescript-eslint/no-unused-vars": [
+          "warn",
+          {
+            "args": "none",
+            "ignoreRestSiblings": true
+          }
+        ],
+        "no-unused-expressions": "off",
+        "@typescript-eslint/no-unused-expressions": [
+          "error",
+          {
+            "allowShortCircuit": true,
+            "allowTernary": true,
+            "allowTaggedTemplates": true
+          }
+        ],
+        "no-useless-constructor": "off",
+        "@typescript-eslint/no-useless-constructor": "warn"
+      }
+    },
+    {
+      "files": [
+        "test/**/*",
+        "examples/**/*",
+        "packages/create-next-app/templates/**/*"
+      ],
+      "rules": { "react/react-in-jsx-scope": "off" }
+    }
+  ],
+  "rules": {
+    "quotes": ["error", "single"],
+    "array-callback-return": "warn",
+    "default-case": ["warn", { "commentPattern": "^no default$" }],
+    "dot-location": ["warn", "property"],
+    "eqeqeq": ["warn", "smart"],
+    "new-parens": "warn",
+    "no-array-constructor": "warn",
+    "no-caller": "warn",
+    "no-cond-assign": ["warn", "except-parens"],
+    "no-const-assign": "warn",
+    "no-control-regex": "warn",
+    "no-delete-var": "warn",
+    "no-dupe-args": "warn",
+    "no-dupe-class-members": "warn",
+    "no-dupe-keys": "warn",
+    "no-duplicate-case": "warn",
+    "no-empty-character-class": "warn",
+    "no-empty-pattern": "warn",
+    "no-eval": "warn",
+    "no-ex-assign": "warn",
+    "no-extend-native": "warn",
+    "no-extra-bind": "warn",
+    "no-extra-label": "warn",
+    "no-fallthrough": "warn",
+    "no-func-assign": "warn",
+    "no-implied-eval": "warn",
+    "no-invalid-regexp": "warn",
+    "no-iterator": "warn",
+    "no-label-var": "warn",
+    "no-labels": ["warn", { "allowLoop": true, "allowSwitch": false }],
+    "no-lone-blocks": "warn",
+    "no-loop-func": "warn",
+    "no-mixed-operators": [
+      "warn",
+      {
+        "groups": [
+          ["&", "|", "^", "~", "<<", ">>", ">>>"],
+          ["==", "!=", "===", "!==", ">", ">=", "<", "<="],
+          ["&&", "||"],
+          ["in", "instanceof"]
+        ],
+        "allowSamePrecedence": false
+      }
+    ],
+    "no-multi-str": "warn",
+    "no-native-reassign": "warn",
+    "no-negated-in-lhs": "warn",
+    "no-new-func": "warn",
+    "no-new-object": "warn",
+    "no-new-symbol": "warn",
+    "no-new-wrappers": "warn",
+    "no-obj-calls": "warn",
+    "no-octal": "warn",
+    "no-octal-escape": "warn",
+    "no-redeclare": ["warn", { "builtinGlobals": false }],
+    "no-regex-spaces": "warn",
+    "no-restricted-syntax": ["warn", "WithStatement"],
+    "no-script-url": "warn",
+    "no-self-assign": "warn",
+    "no-self-compare": "warn",
+    "no-sequences": "warn",
+    "no-shadow-restricted-names": "warn",
+    "no-sparse-arrays": "warn",
+    "no-template-curly-in-string": "error",
+    "no-this-before-super": "warn",
+    "no-throw-literal": "warn",
+    "no-undef": "error",
+    "no-unexpected-multiline": "warn",
+    "no-unreachable": "warn",
+    "no-unused-expressions": [
+      "error",
+      {
+        "allowShortCircuit": true,
+        "allowTernary": true,
+        "allowTaggedTemplates": true
+      }
+    ],
+    "no-unused-labels": "warn",
+    "no-unused-vars": [
+      "warn",
+      {
+        "args": "none",
+        "ignoreRestSiblings": true
+      }
+    ],
+    "no-use-before-define": [
+      "warn",
+      {
+        "functions": false,
+        "classes": false,
+        "variables": false
+      }
+    ],
+    "no-useless-computed-key": "warn",
+    "no-useless-concat": "warn",
+    "no-useless-constructor": "warn",
+    "no-useless-escape": "warn",
+    "no-useless-rename": [
+      "warn",
+      {
+        "ignoreDestructuring": false,
+        "ignoreImport": false,
+        "ignoreExport": false
+      }
+    ],
+    "no-with": "warn",
+    "no-whitespace-before-property": "warn",
+    "react-hooks/exhaustive-deps": "warn",
+    "require-yield": "warn",
+    "rest-spread-spacing": ["warn", "never"],
+    "strict": ["warn", "never"],
+    "unicode-bom": ["warn", "never"],
+    "use-isnan": "warn",
+    "valid-typeof": "warn",
+    "getter-return": "warn",
+    "react/forbid-foreign-prop-types": ["warn", { "allowInPropTypes": true }],
+    "react/jsx-no-comment-textnodes": "warn",
+    "react/jsx-no-duplicate-props": "warn",
+    "react/jsx-no-target-blank": "warn",
+    "react/jsx-no-undef": "error",
+    "react/jsx-pascal-case": [
+      "warn",
+      {
+        "allowAllCaps": true,
+        "ignore": []
+      }
+    ],
+    "react/jsx-uses-react": "warn",
+    "react/jsx-uses-vars": "warn",
+    "react/no-danger-with-children": "warn",
+    "react/no-deprecated": "warn",
+    "react/no-direct-mutation-state": "warn",
+    "react/no-is-mounted": "warn",
+    "react/no-typos": "error",
+    "react/react-in-jsx-scope": "off",
+    "react/require-render-return": "error",
+    "react/style-prop-object": "warn",
+    "react-hooks/rules-of-hooks": "error"
+  }
+}

package.json

@@ -6,7 +6,8 @@
     "dev": "next",
     "build": "next build",
     "start": "next start",
-    "type-check": "tsc"
+    "type-check": "tsc",
+    "lint-eslint": "eslint . --ext js,jsx,ts,tsx --max-warnings=0"
   },
   "dependencies": {
     "@apollo/react-hooks": "^3.1.3",
@@ -26,6 +27,12 @@
     "@types/node": "^13.7.6",
     "@types/react": "^16.9.23",
     "@types/react-dom": "^16.9.5",
+    "@typescript-eslint/eslint-plugin": "^2.21.0",
+    "@typescript-eslint/parser": "^2.21.0",
+    "babel-eslint": "^10.1.0",
+    "eslint": "^6.8.0",
+    "eslint-plugin-react": "^7.18.3",
+    "eslint-plugin-react-hooks": "^2.5.0",
     "typescript": "3.8.2"
   }
 }