Code style/formatting: Prettier + Airbnb ESLint preset (#146)

The purpose of this change is to move toward a more idiomatic code style, and automate as much of it as possible. What's in the change:

- Adds automatic formatting provided by [Prettier](https://prettier.io/)
- Consolidates all ESLint configs into one file via `overrides`
- Extends [Airbnb's ESLint config](https://github.com/airbnb/javascript/tree/master/packages/eslint-config-airbnb), a commonly used, opinionated set of rules
  - Overrides some of those rules to be warnings where they're not automatically fixable; there are _a lot of warnings_, the goal is to fix them wherever we touch code with warnings
  - Manually fixes a very small portion of those warnings where it was trivial and obviously safe
- Extends Prettier's ESLint config to enable checking Prettier rules (e.g. while editing in VSCode and in CI)
- Applies automatic Prettier and ESLint formatting on save in VSCode

I've validated that transforms behave the same before and after this change, with all of the forms under test/forms as well as those from Enketo Core.

.eslintrc.json

@@ -2,16 +2,13 @@
     "env": {
         "es6": true,
         "browser": false,
-        "node": true,
-        "commonjs": false
+        "node": true
     },
     "globals": {
         "Promise": true
     },
-    "extends": "eslint:recommended",
-    "plugins": [
-        "jsdoc"
-    ],
+    "extends": ["airbnb", "prettier"],
+    "plugins": ["chai-friendly", "jsdoc", "prettier", "unicorn"],
     "parserOptions": {
         "sourceType": "module",
         "ecmaVersion": 2019
@@ -24,40 +21,42 @@
         }
     },
     "rules": {
-        "indent": ["warn", 4, { "SwitchCase": 1 }],
-        "linebreak-style": ["error", "unix"],
-        "quotes": ["error", "single"],
-        "semi": ["error", "always"],
-        "no-console": ["warn", { "allow": ["error", "deprecate", "warn"] }],
-        "eol-last": ["error", "always"],
-        "padding-line-between-statements": ["warn", { "blankLine": "always", "prev": "*", "next": "return" }],
-        "space-before-function-paren": ["error", {
-            "anonymous": "never",
-            "named": "never",
-            "asyncArrow": "always"
-        }],
-        "space-in-parens": ["error", "always"],
-        "space-infix-ops": "error",
-        "array-bracket-spacing": ["error", "always"],
-        "no-implied-eval": "error",
-        "object-curly-spacing": ["error", "always"],
-        "jsdoc/check-examples": 1,
-        "jsdoc/check-param-names": 1,
-        "jsdoc/check-tag-names": 1,
-        "jsdoc/check-types": 1,
-        "jsdoc/newline-after-description": ["warn", "always"],
-        "jsdoc/no-undefined-types": 1,
-        "jsdoc/require-description": 0,
-        "jsdoc/require-description-complete-sentence": 0,
-        "jsdoc/require-example": 0,
-        "jsdoc/require-hyphen-before-param-description": 1,
-        "jsdoc/require-param": 1,
-        "jsdoc/require-param-description": 1,
-        "jsdoc/require-param-name": 1,
-        "jsdoc/require-param-type": 1,
-        "jsdoc/require-returns-check": 1,
-        "jsdoc/require-returns-description": 1,
-        "jsdoc/require-returns-type": 1,
-        "jsdoc/valid-types": 1
-    }
+        "prettier/prettier": "error",
+
+        "guard-for-in": "warn",
+        "import/extensions": "warn",
+        "import/order": "warn",
+        "no-param-reassign": "warn",
+        "no-restricted-syntax": [
+            "warn",
+            "ForInStatement",
+            "LabeledStatement",
+            "WithStatement"
+        ],
+        "no-shadow": "warn",
+        "no-underscore-dangle": "warn",
+        "no-use-before-define": [
+            "warn",
+            {
+                "functions": false
+            }
+        ],
+        "prefer-destructuring": "warn"
+    },
+    "overrides": [
+        {
+            "files": ["./.github/**/*.md", "./*.md"],
+            "parser": "markdown-eslint-parser",
+            "rules": {
+                "prettier/prettier": ["error", { "parser": "markdown" }]
+            }
+        },
+
+        {
+            "files": ["./test/**/*.js"],
+            "env": {
+                "mocha": true
+            }
+        }
+    ]
 }

.github/workflows/npmjs.yml

@@ -1,35 +1,35 @@
 name: npmjs
 
 on:
-  push:
-  pull_request:
-  release:
-    types:
-      - published
+    push:
+    pull_request:
+    release:
+        types:
+            - published
 
 jobs:
-  build:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        node: [ '14', '16' ]
-    steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v2
-        id: cache
-        with:
-          path: node_modules
-          key: ${{ matrix.node }}-${{ hashFiles('**/package-lock.json') }}
-      - uses: actions/setup-node@v2
-        with:
-          node-version: ${{ matrix.node }}
-          registry-url: https://registry.npmjs.org/
-      - run: npm install -g npm@^6
-      - if: steps.cache.outputs.cache-hit != 'true'
-        run: npm ci
-      - run: npm test
-      - run: npm run build-docs
-      - if: github.event_name == 'release' && github.event.action == 'published' && matrix.node == '16'
-        run: npm publish
-        env:
-          NODE_AUTH_TOKEN: ${{secrets.npm_token}}
+    build:
+        runs-on: ubuntu-latest
+        strategy:
+            matrix:
+                node: ['14', '16']
+        steps:
+            - uses: actions/checkout@v2
+            - uses: actions/cache@v2
+              id: cache
+              with:
+                  path: node_modules
+                  key: ${{ matrix.node }}-${{ hashFiles('**/package-lock.json') }}
+            - uses: actions/setup-node@v2
+              with:
+                  node-version: ${{ matrix.node }}
+                  registry-url: https://registry.npmjs.org/
+            - run: npm install -g npm@^6
+            - if: steps.cache.outputs.cache-hit != 'true'
+              run: npm ci
+            - run: npm test
+            - run: npm run build-docs
+            - if: github.event_name == 'release' && github.event.action == 'published' && matrix.node == '16'
+              run: npm publish
+              env:
+                  NODE_AUTH_TOKEN: ${{secrets.npm_token}}

.prettierignore

@@ -0,0 +1,6 @@
+# Ignore artifacts:
+
+.nyc*
+*/node_modules/*
+docs/*
+test-coverage/*

.prettierrc.json

@@ -0,0 +1,5 @@
+{
+    "$schema": "http://json.schemastore.org/prettierrc",
+    "singleQuote": true,
+    "trailingComma": "es5"
+}

.vscode/launch.json

@@ -3,14 +3,9 @@
         {
             "name": "Test (watch + debug)",
             "request": "launch",
-            "runtimeArgs": [
-                "run-script",
-                "test:watch"
-            ],
+            "runtimeArgs": ["run-script", "test:watch"],
             "runtimeExecutable": "npm",
-            "skipFiles": [
-                "<node_internals>/**"
-            ],
+            "skipFiles": ["<node_internals>/**"],
             "type": "pwa-node",
             "sourceMaps": true,
             "console": "integratedTerminal"

.vscode/settings.json

@@ -1,8 +1,28 @@
 {
+    // Formatting
+    "eslint.enable": true,
     "eslint.options": {
-        "rules": {
-            "no-debugger": 1 // Warn rather than error in-editor
-        }
+        "extends": ["../.eslintrc.json"]
     },
+    "eslint.nodePath": "../node_modules/.bin",
+    "eslint.validate": ["markdown", "md"],
+    "prettier.configPath": ".prettierrc.json",
+    "prettier.ignorePath": ".prettierignore",
+    "editor.defaultFormatter": "esbenp.prettier-vscode",
+    "editor.codeActionsOnSave": [
+        "source.formatDocument",
+        "source.fixAll.eslint"
+    ],
+    "editor.formatOnSave": true,
+    "[javascript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+    "[typescript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+
+    // Code navigation
     "javascript.referencesCodeLens.enabled": true
 }