chore: add linter strict-boolean-expressions

.circleci/config.yml

@@ -23,6 +23,7 @@ jobs:
                   paths:
                       - node_modules
                   key: v1-dependencies-{{ checksum "yarn.lock" }}
+            - run: yarn eslint
             - run: yarn build
             - save_cache:
                   paths:

.eslintignore

@@ -0,0 +1,6 @@
+es
+doc
+temp
+*.spec.ts
+*.test.ts
+umd

.eslintrc

@@ -0,0 +1,37 @@
+{
+  "parserOptions": {
+    "ecmaVersion": 2020,
+    "sourceType": "module",
+    "project": "./tsconfig.json"
+  },
+  "parser": "@typescript-eslint/parser",
+  "plugins": ["@typescript-eslint"],
+  "extends": [],
+  "env": {},
+  "rules": {
+    "no-debugger": "error",
+    "no-plusplus": "error",
+    "no-bitwise": "error",
+    "no-new-wrappers": "error",
+    "constructor-super": "error",
+    "no-redeclare": "error",
+    "no-eval": "error",
+    "no-template-curly-in-string": "error",
+    "no-return-await": "error",
+    "no-sparse-arrays": "error",
+    "dot-notation": "error",
+    "no-fallthrough": "error",
+    "prefer-const": "error",
+    "eqeqeq": "error",
+    "no-extra-bind": "error",
+    "use-isnan": "error",
+    "@typescript-eslint/strict-boolean-expressions": [
+      2,
+      {
+        "allowNullable": true,
+        "allowSafe": true,
+        "ignoreRhs": true
+      }
+    ]
+  }
+}

package.json

@@ -25,6 +25,8 @@
     "build": "cross-env NODE_ENV=production npm-run-all --parallel clean \"build:tsc -- {@}\" build:rollup",
     "build:tsc": "tsc",
     "build:rollup": "rollup -c -m",
+    "eslint": "eslint . --ext .ts,.tsx",
+    "eslint:watch": "yarn esw . --ext .ts,.tsx -w --color",
     "clean": "rimraf ./es ./umd",
     "prepublishOnly": "npm run build",
     "doc": "npm-run-all --serial build:tsc doc:api doc:md",
@@ -38,7 +40,11 @@
     "@rollup/plugin-replace": "^2.3.1",
     "@types/lodash-es": "^4.1.4",
     "@types/mocha": "^7.0.1",
+    "@typescript-eslint/eslint-plugin": "^2.19.0",
+    "@typescript-eslint/parser": "^2.19.0",
     "cross-env": "^7.0.0",
+    "eslint": "^6.8.0",
+    "eslint-watch": "^6.0.1",
     "jsdom": "^16.1.0",
     "jsdom-global": "^3.0.2",
     "mocha": "^7.0.1",

src/DOM/Proxy.ts

@@ -58,7 +58,7 @@ export function DOMProxy<
     let virtualAfter: After | null = null
     let virtualAfterShadow: ShadowRoot | null = null
     /** All changes applied on the `proxy` */
-    let changes: ActionTypes[keyof ActionTypes][] = []
+    const changes: ActionTypes[keyof ActionTypes][] = []
     /** Read Traps */
     const readonlyTraps: ProxyHandler<any> = {
         ownKeys: () => {
@@ -132,7 +132,7 @@ export function DOMProxy<
     const modifyTrapsNotWrite = modifyTraps(false)
     const proxy = Proxy.revocable(defaultCurrent, { ...readonlyTraps, ...modifyTrapsWrite })
     function hasStyle(e: Node): e is HTMLElement {
-        return !!(e as any).style
+        return 'style' in e
     }
     /** Call before realCurrent change */
     function undoEffects(nextCurrent?: Node | null) {
@@ -144,7 +144,7 @@ export function DOMProxy<
                 } else if (attr === 'appendChild') {
                     if (!nextCurrent) {
                         const node = (change.op.thisArg as Parameters<HTMLElement['appendChild']>)[0]
-                        node && current.removeChild(node)
+                        if (node !== undefined) current.removeChild(node)
                     }
                 }
             } else if (change.type === 'modifyStyle') {
@@ -170,7 +170,7 @@ export function DOMProxy<
                 const replayable = ['appendChild', 'addEventListener', 'before', 'after']
                 const key: keyof Node = change.op.name as any
                 if (replayable.indexOf(key) !== -1) {
-                    if (current[key]) {
+                    if (current[key] !== undefined) {
                         ;(current[key] as any)(...change.op.param)
                     } else {
                         console.warn(current, `doesn't have method "${key}", replay failed.`)
@@ -294,6 +294,7 @@ export function DOMProxy<
     DOMProxyDevtoolsEnhancer.allDOMProxy.set(DOMProxyObject, changes)
     return DOMProxyObject
 }
+// eslint-disable-next-line no-redeclare
 export namespace DOMProxy {
     export function enhanceDebugger() {
         installCustomObjectFormatter(new DOMProxyDevtoolsEnhancer())

src/DOM/Watcher.ts

@@ -607,7 +607,7 @@ export abstract class Watcher<T, Before extends Element, After extends Element,
     /** window.requestIdleCallback, or polyfill. */
     protected readonly requestIdleCallback = requestIdleCallback
     /** For debug usage. Just keep it. */
-    private readonly stack = new Error().stack || ''
+    private readonly stack = new Error().stack ?? ''
     //#endregion
     //#region Warnings
     /**
@@ -722,10 +722,10 @@ type useForeachReturns<T> =
 
 function applyUseForeachCallback<T>(callback: useForeachReturns<T>) {
     const cb = callback as useForeachReturns<Node>
-    let remove: any, change: any, mutation: any
-    if (cb === undefined) {
-    } else if (typeof cb === 'function') remove = cb
-    else if (cb) {
+    type f = undefined | ((...args: any[]) => any)
+    let remove: f, change: f, mutation: f
+    if (typeof cb === 'function') remove = cb
+    else if (cb !== undefined) {
         const { onNodeMutation, onRemove, onTargetChanged } = cb
         ;[remove, change, mutation] = [onRemove, onTargetChanged, onNodeMutation]
     }
@@ -759,17 +759,17 @@ interface WarningOptions {
 function warning(_: Partial<WarningOptions> = {}) {
     const { dev, once, fn } = { ...({ dev: false, once: true, fn: () => {} } as WarningOptions), ..._ }
     if (dev) if (process.env.NODE_ENV !== 'development') return { warn(f = fn) {}, ignored: true, stack: '' }
-    const [_0, _1, _2, ...lines] = (new Error().stack || '').split('\n')
+    const [_0, _1, _2, ...lines] = (new Error().stack ?? '').split('\n')
     const stack = lines.join('\n')
     let warned = 0
     const obj = {
         ignored: false,
         stack,
         warn(f = fn) {
             if (obj.ignored) return
-            if (warned && once) return
+            if (warned > 0 && once) return
             if (typeof once === 'number' && warned <= once) return
-            warned++
+            warned = warned + 1
             f(stack)
         },
     }

src/Debuggers/DOMProxyDevtoolsEnhancer.tsx

@@ -29,7 +29,7 @@ export class DOMProxyDevtoolsEnhancer implements React.CustomObjectFormatter {
     decorateShadow(obj: ShadowRoot) {
         return <span>{`#shadow-root (${obj.mode})`}</span>
     }
-    body(obj: DOMProxy<any, any, any>, clearState: boolean) {
+    body(obj: DOMProxy<Node, Element, Element>, clearState: boolean) {
         const [state, setState, render] = React.useState(obj, x)
         if (clearState) setState({ refreshed: false })
 

src/Debuggers/LiveSelectorDevtoolsEnhancer.tsx

@@ -98,7 +98,7 @@ export class LiveSelectorDevtoolsEnhancer implements React.CustomObjectFormatter
             // @ts-ignore
             initialElements: obj.initialElements,
             // @ts-ignore
-            stack: obj.stack || '',
+            stack: obj.stack ?? '',
             // @ts-ignore
             selectorChain: obj.selectorChain,
         }

src/Debuggers/WatcherDevtoolsEnhancer.tsx

@@ -90,6 +90,10 @@ export class WatcherDevtoolsEnhancer implements React.CustomObjectFormatter {
             setState({ refreshed: true })
             forceRender()
         }
+        function isNil(x: any): boolean {
+            if (x === null || x === undefined) return false
+            return true
+        }
         return (
             <div>
                 <span variant={['fade']}>Last values:</span>
@@ -102,13 +106,17 @@ export class WatcherDevtoolsEnhancer implements React.CustomObjectFormatter {
                 <span variant={['fade']}>Other:</span>
                 <table>
                     {this.optionsRow('LiveSelector', priv.liveSelector, () => false)}
-                    {this.optionsRow('ConsistentWatchRoot', priv.consistentWatchRoot, x => x === document.body || !x)}
+                    {this.optionsRow(
+                        'ConsistentWatchRoot',
+                        priv.consistentWatchRoot,
+                        x => x === document.body || isNil(x),
+                    )}
                     {this.optionsRow('DomProxyOptions', priv.domProxyOption, x => Object.keys(x).length === 0)}
                     {this.optionsRow('KeyComparer', priv.keyComparer, x => x(test, test))}
                     {this.optionsRow('ValueComparer', priv.valueComparer, x => x(test, test))}
                     {this.optionsRow('MapNodeToKey', priv.mapNodeToKey, x => x(test, 0, []) === test)}
                     {this.optionsRow('FirstDOMProxy', obj.firstDOMProxy, x => true)}
-                    {this.optionsRow('stopWatchOnDisconnected', priv.stopWatchOnDisconnected, x => !x)}
+                    {this.optionsRow('stopWatchOnDisconnected', priv.stopWatchOnDisconnected, isNil)}
                 </table>
                 <br />
                 <div variant={['bigint']}>Actions:</div>

src/Extension/AutomatedTabTask.ts

@@ -210,7 +210,7 @@ export function AutomatedTabTask<T extends Record<string, (...args: any[]) => Pr
 
             let finalURL: string
             if (typeof urlOrTabID === 'string') finalURL = urlOrTabID
-            else finalURL = url || ''
+            else finalURL = url ?? ''
             function proxyTrap(_target: unknown, taskName: string | number | symbol) {
                 return (...taskArgs: any[]) => {
                     if (typeof taskName !== 'string') throw new TypeError('Key must be a string')

src/Extension/Context.ts

@@ -13,17 +13,18 @@ export type Contexts = 'background' | 'content' | 'webpage' | 'unknown' | 'optio
  */
 export function GetContext(): Contexts {
     if (typeof location === 'undefined') return 'unknown'
-    if (typeof browser !== 'undefined') {
-        if (location.protocol.match('-extension')) {
+    if (typeof browser !== 'undefined' && browser !== null) {
+        const scheme = location.protocol.match('-extension')
+        const backgroundURL = browser.extension?.getBackgroundPage()?.location?.href
+        if (scheme || location.hostname === 'localhost') {
             if (
-                browser.extension && browser.extension.getBackgroundPage
-                    ? browser.extension.getBackgroundPage().location.href === location.href
-                    : ['generated', 'background', 'page', '.html'].every(x => location.pathname.match(x))
+                backgroundURL === location.href ||
+                ['generated', 'background', 'page', '.html'].every(x => location.pathname.match(x))
             )
                 return 'background'
-            return 'options'
         }
-        if (browser.runtime && browser.runtime.getManifest) return 'content'
+        if (scheme) return 'options'
+        if (browser.runtime?.getManifest !== undefined) return 'content'
     }
     // What about rollup?
     if (location.hostname === 'localhost') return 'debugging'

src/Extension/MessageCenter.ts

@@ -32,10 +32,10 @@ export class MessageCenter<ITypedMessages> {
     public serialization: Serialization = NoSerialization
     private eventEmitter = mitt()
     private listener = async (request: unknown) => {
-        let { key, data, instanceKey } = (await this.serialization.deserialization(request)) as InternalMessageType
+        const { key, data, instanceKey } = (await this.serialization.deserialization(request)) as InternalMessageType
         // Message is not for us
-        if (this.instanceKey !== (instanceKey || '')) return
-        if (!key || !data) return
+        if (this.instanceKey !== (instanceKey ?? '')) return
+        if (key === undefined) return
         if (this.log) {
             console.log(
                 `%cReceive%c %c${key.toString()}`,
@@ -97,14 +97,14 @@ export class MessageCenter<ITypedMessages> {
         const serialized = await this.serialization.serialization({
             data,
             key,
-            instanceKey: this.instanceKey || '',
+            instanceKey: this.instanceKey ?? '',
         } as InternalMessageType)
         if (typeof browser !== 'undefined') {
             browser.runtime?.sendMessage?.(serialized).catch(noop)
             // Send message to Content Script
             browser.tabs?.query({ discarded: false }).then(tabs => {
                 for (const tab of tabs) {
-                    if (tab.id) browser.tabs.sendMessage(tab.id, serialized).catch(noop)
+                    if (tab.id !== undefined) browser.tabs.sendMessage(tab.id, serialized).catch(noop)
                 }
             })
         }

src/util/sleep.ts

@@ -22,7 +22,7 @@ export const timeout = <T>(promise: PromiseLike<T>, time: number, rejectReason?:
     const race = Promise.race([
         promise,
         new Promise<T>((r, reject) => {
-            timer = setTimeout(() => reject(new Error(rejectReason || 'timeout')), time)
+            timer = setTimeout(() => reject(new Error(rejectReason ?? 'timeout')), time)
         }),
     ])
     race.finally(() => clearTimeout(timer))