refactor: enable no-unnecessary-condition

eslint.config.js

@@ -28,6 +28,11 @@ export default tseslint.config(
       '**/*.snap',
     ],
   },
+  {
+    linterOptions: {
+      reportUnusedDisableDirectives: shouldTypeCheck ? 'warn' : 'off',
+    },
+  },
   eslint.configs.recommended,
   ...tseslint.configs.recommended,
   ...tseslint.configs.stylistic,
@@ -145,6 +150,16 @@ export default tseslint.config(
       '@typescript-eslint/consistent-type-definitions': 'off',
       '@typescript-eslint/prefer-for-of': 'off',
       '@typescript-eslint/prefer-function-type': 'off',
+      ...(shouldTypeCheck
+        ? {
+            '@typescript-eslint/no-unnecessary-condition': [
+              'error',
+              {
+                allowConstantLoopConditions: true,
+              },
+            ],
+          }
+        : {}),
 
       'import-x/no-nodejs-modules': [
         'error',
@@ -346,5 +361,8 @@ export default tseslint.config(
         project: false,
       },
     },
+    rules: {
+      '@typescript-eslint/no-unnecessary-condition': 'off',
+    },
   },
 )

packages/create-vite/src/index.ts

@@ -289,9 +289,10 @@ const FRAMEWORKS: Framework[] = [
   },
 ]
 
-const TEMPLATES = FRAMEWORKS.map(
-  (f) => (f.variants && f.variants.map((v) => v.name)) || [f.name],
-).reduce((a, b) => a.concat(b), [])
+const TEMPLATES = FRAMEWORKS.map((f) => f.variants.map((v) => v.name)).reduce(
+  (a, b) => a.concat(b),
+  [],
+)
 
 const renameFiles: Record<string, string | undefined> = {
   _gitignore: '.gitignore',
@@ -394,8 +395,8 @@ async function init() {
           }),
         },
         {
-          type: (framework: Framework) =>
-            framework && framework.variants ? 'select' : null,
+          type: (framework: Framework | /* package name */ string) =>
+            typeof framework === 'object' ? 'select' : null,
           name: 'variant',
           message: reset('Select a variant:'),
           choices: (framework: Framework) =>
@@ -478,7 +479,7 @@ async function init() {
     const replacedArgs = args.map((arg) =>
       arg.replace('TARGET_DIR', () => targetDir),
     )
-    const { status } = spawn.sync(command, replacedArgs, {
+    const { status } = spawn.sync(command!, replacedArgs, {
       stdio: 'inherit',
     })
     process.exit(status ?? 0)
@@ -596,11 +597,11 @@ function emptyDir(dir: string) {
 
 function pkgFromUserAgent(userAgent: string | undefined) {
   if (!userAgent) return undefined
-  const pkgSpec = userAgent.split(' ')[0]
+  const pkgSpec = userAgent.split(' ')[0]!
   const pkgSpecArr = pkgSpec.split('/')
   return {
-    name: pkgSpecArr[0],
-    version: pkgSpecArr[1],
+    name: pkgSpecArr[0]!,
+    version: pkgSpecArr[1] ?? '',
   }
 }
 

packages/create-vite/tsconfig.json

@@ -10,6 +10,7 @@
     "declaration": false,
     "sourceMap": false,
     "noUnusedLocals": true,
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "noUncheckedIndexedAccess": true
   }
 }

packages/plugin-legacy/src/index.ts

@@ -717,7 +717,7 @@ function viteLegacyPlugin(options: Options = {}): Plugin[] {
       if (isLegacyBundle(bundle, opts) && genModern) {
         // avoid emitting duplicate assets
         for (const name in bundle) {
-          if (bundle[name].type === 'asset' && !/.+\.map$/.test(name)) {
+          if (bundle[name]!.type === 'asset' && !/.+\.map$/.test(name)) {
             delete bundle[name]
           }
         }
@@ -831,7 +831,7 @@ async function buildPolyfillChunk(
       },
     },
   })
-  const _polyfillChunk = Array.isArray(res) ? res[0] : res
+  const _polyfillChunk = Array.isArray(res) ? res[0]! : res
   if (!('output' in _polyfillChunk)) return
   const polyfillChunk = _polyfillChunk.output.find(
     (chunk) => chunk.type === 'chunk' && chunk.isEntry,
@@ -840,7 +840,7 @@ async function buildPolyfillChunk(
   // associate the polyfill chunk to every entry chunk so that we can retrieve
   // the polyfill filename in index html transform
   for (const key in bundle) {
-    const chunk = bundle[key]
+    const chunk = bundle[key]!
     if (chunk.type === 'chunk' && chunk.facadeModuleId) {
       facadeToChunkMap.set(chunk.facadeModuleId, polyfillChunk.fileName)
     }
@@ -971,7 +971,7 @@ function wrapIIFEBabelPlugin(): BabelPlugin {
 }
 
 const hash =
-  // eslint-disable-next-line n/no-unsupported-features/node-builtins -- crypto.hash is supported in Node 21.7.0+, 20.12.0+
+  // eslint-disable-next-line n/no-unsupported-features/node-builtins, @typescript-eslint/no-unnecessary-condition -- crypto.hash is supported in Node 21.7.0+, 20.12.0+
   crypto.hash ??
   ((
     algorithm: string,

packages/plugin-legacy/tsconfig.json

@@ -11,6 +11,7 @@
     "sourceMap": true,
     "noUnusedLocals": true,
     "esModuleInterop": true,
+    "noUncheckedIndexedAccess": true,
     "paths": {
       "vite": ["../vite/src/node/index.js"]
     }

packages/vite/rollup.config.ts

@@ -242,7 +242,7 @@ function shimDepsPlugin(deps: Record<string, ShimOptions[]>): Plugin {
     transform(code, id) {
       for (const file in deps) {
         if (id.replace(/\\/g, '/').endsWith(file)) {
-          for (const { src, replacement, pattern } of deps[file]) {
+          for (const { src, replacement, pattern } of deps[file]!) {
             const magicString = new MagicString(code)
 
             if (src) {

packages/vite/rollup.dts.config.ts

@@ -182,7 +182,7 @@ function replaceConfusingTypeNames(
         continue
       }
 
-      const betterId = replacements[id]
+      const betterId = replacements[id]!
       const regexEscapedId = escapeRegex(id)
       // If the better id accesses a namespace, the existing `Foo as Foo$1`
       // named import cannot be replaced with `Foo as Namespace.Foo`, so we

packages/vite/rollupLicensePlugin.ts

@@ -28,11 +28,11 @@ export default function licensePlugin(
       let dependencyLicenseTexts = ''
       for (let i = 0; i < deps.length; i++) {
         // Find dependencies with the same license text so it can be shared
-        const licenseText = deps[i].licenseText
-        const sameDeps = [deps[i]]
+        const licenseText = deps[i]!.licenseText
+        const sameDeps = [deps[i]!]
         if (licenseText) {
           for (let j = i + 1; j < deps.length; j++) {
-            if (licenseText === deps[j].licenseText) {
+            if (licenseText === deps[j]!.licenseText) {
               sameDeps.push(...deps.splice(j, 1))
               j--
             }
@@ -47,11 +47,11 @@ export default function licensePlugin(
           depInfos.length > 1 &&
           depInfos.every(
             (info) =>
-              info.license === depInfos[0].license &&
-              info.names === depInfos[0].names,
+              info.license === depInfos[0]!.license &&
+              info.names === depInfos[0]!.names,
           )
         ) {
-          const { license, names } = depInfos[0]
+          const { license, names } = depInfos[0]!
           const repositoryText = depInfos
             .map((info) => info.repository)
             .filter(Boolean)
@@ -64,7 +64,7 @@ export default function licensePlugin(
         // Else show each dependency separately
         else {
           for (let j = 0; j < depInfos.length; j++) {
-            const { license, names, repository } = depInfos[j]
+            const { license, names, repository } = depInfos[j]!
 
             if (license) text += `License: ${license}\n`
             if (names) text += `By: ${names}\n`

packages/vite/src/client/client.ts

@@ -140,7 +140,10 @@ const hmrClient = new HMRClient(
     explicitImportRequired,
     isWithinCircularImport,
   }) {
-    const [acceptedPathWithoutQuery, query] = acceptedPath.split(`?`)
+    const [acceptedPathWithoutQuery, query] = acceptedPath.split(`?`) as [
+      string,
+      ...string[],
+    ]
     const importPromise = import(
       /* @vite-ignore */
       base +
@@ -309,6 +312,7 @@ const hasDocument = 'document' in globalThis
 function createErrorOverlay(err: ErrorPayload['err']) {
   clearErrorOverlay()
   const { customElements } = globalThis
+  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
   if (customElements) {
     const ErrorOverlayConstructor = customElements.get(overlayId)!
     document.body.appendChild(new ErrorOverlayConstructor(err))

packages/vite/src/client/env.ts

@@ -18,7 +18,7 @@ Object.keys(defines).forEach((key) => {
   const segments = key.split('.')
   let target = context
   for (let i = 0; i < segments.length; i++) {
-    const segment = segments[i]
+    const segment = segments[i]!
     if (i === segments.length - 1) {
       target[segment] = defines[key]
     } else {

packages/vite/src/client/overlay.ts

@@ -225,7 +225,10 @@ export class ErrorOverlay extends HTMLElement {
     }
     this.text('.message-body', message.trim())
 
-    const [file] = (err.loc?.file || err.id || 'unknown file').split(`?`)
+    const [file] = (err.loc?.file || err.id || 'unknown file').split(`?`) as [
+      string,
+      ...string[],
+    ]
     if (err.loc) {
       this.text('.file', `${file}:${err.loc.line}:${err.loc.column}`, links)
     } else if (err.id) {
@@ -264,23 +267,21 @@ export class ErrorOverlay extends HTMLElement {
       fileRE.lastIndex = 0
       while ((match = fileRE.exec(text))) {
         const { 0: file, index } = match
-        if (index != null) {
-          const frag = text.slice(curIndex, index)
-          el.appendChild(document.createTextNode(frag))
-          const link = document.createElement('a')
-          link.textContent = file
-          link.className = 'file-link'
-          link.onclick = () => {
-            fetch(
-              new URL(
-                `${base}__open-in-editor?file=${encodeURIComponent(file)}`,
-                import.meta.url,
-              ),
-            )
-          }
-          el.appendChild(link)
-          curIndex += frag.length + file.length
+        const frag = text.slice(curIndex, index)
+        el.appendChild(document.createTextNode(frag))
+        const link = document.createElement('a')
+        link.textContent = file
+        link.className = 'file-link'
+        link.onclick = () => {
+          fetch(
+            new URL(
+              `${base}__open-in-editor?file=${encodeURIComponent(file)}`,
+              import.meta.url,
+            ),
+          )
         }
+        el.appendChild(link)
+        curIndex += frag.length + file.length
       }
     }
   }
@@ -292,6 +293,7 @@ export class ErrorOverlay extends HTMLElement {
 
 export const overlayId = 'vite-error-overlay'
 const { customElements } = globalThis // Ensure `customElements` is defined before the next line.
+// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
 if (customElements && !customElements.get(overlayId)) {
   customElements.define(overlayId, ErrorOverlay)
 }

packages/vite/src/module-runner/hmrHandler.ts

@@ -151,11 +151,11 @@ function getModulesEntrypoints(
     if (!module) {
       continue
     }
-    if (module.importers && !module.importers.size) {
+    if (!module.importers.size) {
       entrypoints.add(module.url)
       continue
     }
-    for (const importer of module.importers || []) {
+    for (const importer of module.importers) {
       getModulesEntrypoints(runner, [importer], visited, entrypoints)
     }
   }
@@ -167,7 +167,7 @@ function findAllEntrypoints(
   entrypoints = new Set<string>(),
 ): Set<string> {
   for (const mod of runner.evaluatedModules.idToModuleMap.values()) {
-    if (mod.importers && !mod.importers.size) {
+    if (!mod.importers.size) {
       entrypoints.add(mod.url)
     }
   }

packages/vite/src/module-runner/runner.ts

@@ -347,6 +347,7 @@ export class ModuleRunner {
 
     const { code, file } = fetchResult
 
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- is this needed?
     if (code == null) {
       const importer = callstack[callstack.length - 2]
       throw new Error(

packages/vite/src/module-runner/sourcemap/index.ts

@@ -14,6 +14,7 @@ export function enableSourceMapSupport(runner: ModuleRunner): () => void {
         `Cannot use "sourcemapInterceptor: 'node'" because "process.setSourceMapsEnabled" function is not available. Please use Node >= 16.6.0.`,
       )
     }
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- process.sourceMapsEnabled is not available in Node < 20.7.0
     const isEnabledAlready = process.sourceMapsEnabled ?? false
     process.setSourceMapsEnabled(true)
     return () => !isEnabledAlready && process.setSourceMapsEnabled(false)

packages/vite/src/module-runner/sourcemap/interceptor.ts

@@ -3,6 +3,7 @@ import type { ModuleRunner } from '../runner'
 import { posixDirname, posixResolve } from '../utils'
 import type { EvaluatedModules } from '../evaluatedModules'
 import { slash } from '../../shared/utils'
+import type { StrictRegExpExecArrayFromLen } from '../../shared/typeUtils'
 import { DecodedMap, getOriginalPosition } from './decoder'
 
 interface RetrieveFileHandler {
@@ -172,7 +173,8 @@ function retrieveSourceMap(source: string) {
 
 function mapSourcePosition(position: OriginalMapping) {
   if (!position.source) return position
-  let sourceMap = getRunnerSourceMap(position)
+  let sourceMap: CachedMapEntry | null | undefined =
+    getRunnerSourceMap(position)
   if (!sourceMap) sourceMap = sourceMapCache[position.source]
   if (!sourceMap) {
     // Call the (overrideable) retrieveSourceMap function to get the source map.
@@ -210,7 +212,7 @@ function mapSourcePosition(position: OriginalMapping) {
   }
 
   // Resolve the source URL relative to the URL of the source map
-  if (sourceMap && sourceMap.map && sourceMap.url) {
+  if (sourceMap.map && sourceMap.url) {
     const originalPosition = getOriginalPosition(sourceMap.map, position)
 
     // Only return the original position if a matching line was found. If no
@@ -238,7 +240,9 @@ function mapSourcePosition(position: OriginalMapping) {
 // https://code.google.com/p/v8/source/browse/trunk/src/messages.js
 function mapEvalOrigin(origin: string): string {
   // Most eval() calls are in this format
-  let match = /^eval at ([^(]+) \((.+):(\d+):(\d+)\)$/.exec(origin)
+  const match = /^eval at ([^(]+) \((.+):(\d+):(\d+)\)$/.exec(
+    origin,
+  ) as StrictRegExpExecArrayFromLen<4> | null
   if (match) {
     const position = mapSourcePosition({
       name: null,
@@ -250,8 +254,10 @@ function mapEvalOrigin(origin: string): string {
   }
 
   // Parse nested eval() calls using recursion
-  match = /^eval at ([^(]+) \((.+)\)$/.exec(origin)
-  if (match) return `eval at ${match[1]} (${mapEvalOrigin(match[2])})`
+  const match2 = /^eval at ([^(]+) \((.+)\)$/.exec(
+    origin,
+  ) as StrictRegExpExecArrayFromLen<2> | null
+  if (match2) return `eval at ${match2[1]} (${mapEvalOrigin(match2[2])})`
 
   // Make sure we still return useful information if we didn't find anything
   return origin
@@ -345,7 +351,7 @@ function cloneCallSite(frame: CallSite) {
 }
 
 function wrapCallSite(frame: CallSite, state: State) {
-  // provides interface backward compatibility
+  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- provides interface backward compatibility
   if (state === undefined) state = { nextPosition: null, curPosition: null }
 
   if (frame.isNative()) {
@@ -425,7 +431,7 @@ function prepareStackTrace(error: Error, stack: CallSite[]) {
   const state = { nextPosition: null, curPosition: null }
   const processedStack = []
   for (let i = stack.length - 1; i >= 0; i--) {
-    processedStack.push(`\n    at ${wrapCallSite(stack[i], state)}`)
+    processedStack.push(`\n    at ${wrapCallSite(stack[i]!, state)}`)
     state.nextPosition = state.curPosition
   }
   state.curPosition = state.nextPosition = null