Finish enabling ts-eslint (#5944)

- prefer `null`, `!= null` and `== null` instead of `undefined`
- disallow `as`, add comments for the existing usages of `as`
- make `tsconfig.json` a bit stricter
- minor fixes to other files that were missed

# Important Notes
N/A

app/ide-desktop/esbuild-watch.ts

@@ -1,4 +1,4 @@
-/** Helper module for running esbuild in watch mode. */
+/** @file A helper module for running esbuild in watch mode. */
 
 import * as esbuild from 'esbuild'
 
@@ -6,21 +6,20 @@ import * as esbuild from 'esbuild'
  * @param config - Configuration for the esbuild command.
  * @param onRebuild - Callback to be called after each rebuild.
  * @param inject - See [esbuild docs](https://esbuild.github.io/api/#inject).
- *
+ */
- **/
+export function toWatchOptions<T extends esbuild.BuildOptions>(
-export function toWatchOptions(
+    config: T,
-    config: esbuild.BuildOptions,
     onRebuild?: () => void,
     inject?: esbuild.BuildOptions['inject']
-): esbuild.BuildOptions {
+) {
     return {
         ...config,
         inject: [...(config.inject ?? []), ...(inject ?? [])],
         watch: {
-            onRebuild(error, result) {
+            onRebuild(error) {
                 if (error) console.error('watch build failed:', error)
                 else onRebuild?.()
             },
         },
-    }
+    } satisfies esbuild.BuildOptions
 }

app/ide-desktop/eslint.config.js

@@ -29,7 +29,7 @@ const ALLOWED_DEFAULT_IMPORT_MODULES = `${DEFAULT_IMPORT_ONLY_MODULES}|react-hot
 const OUR_MODULES = 'enso-content-config|enso-common'
 const RELATIVE_MODULES =
     'bin\\u002Fproject-manager|bin\\u002Fserver|config\\u002Fparser|authentication|config|debug|index|ipc|naming|paths|preload|security'
-const STRING_LITERAL = 'Literal[raw=/^["\']/]'
+const STRING_LITERAL = ':matches(Literal[raw=/^["\']/], TemplateLiteral)'
 const JSX = ':matches(JSXElement, JSXFragment)'
 const NOT_PASCAL_CASE = '/^(?!_?([A-Z][a-z0-9]*)+$)/'
 const NOT_CAMEL_CASE = '/^(?!_?[a-z][a-z0-9*]*([A-Z0-9][a-z0-9]*)*$)/'
@@ -102,7 +102,7 @@ const RESTRICTED_SYNTAXES = [
     },
     {
         selector:
-            ':not(:matches(FunctionDeclaration, FunctionExpression, ArrowFunctionExpression, SwitchStatement, SwitchCase, IfStatement:has(.consequent > :matches(ReturnStatement, ThrowStatement)):has(.alternate :matches(ReturnStatement, ThrowStatement)))) > * > ReturnStatement',
+            ':not(:matches(FunctionDeclaration, FunctionExpression, ArrowFunctionExpression, SwitchStatement, SwitchCase, IfStatement:has(.consequent > :matches(ReturnStatement, ThrowStatement)):has(.alternate :matches(ReturnStatement, ThrowStatement)), TryStatement:has(.block > :matches(ReturnStatement, ThrowStatement)):has(:matches([handler=null], .handler :matches(ReturnStatement, ThrowStatement))):has(:matches([finalizer=null], .finalizer :matches(ReturnStatement, ThrowStatement))))) > * > ReturnStatement',
         message: 'No early returns',
     },
     {
@@ -139,8 +139,18 @@ const RESTRICTED_SYNTAXES = [
         message: 'Use `as const` for top-level object literals only containing string literals',
     },
     {
-        selector: ':matches(TSNullKeyword, Literal[raw=null])',
+        // Matches `as T` in either:
-        message: 'Use `undefined` instead of `null`',
+        // - anything other than a variable declaration
+        // - a variable declaration that is not at the top level
+        // - a top-level variable declaration that shouldn't be `as const`
+        // - a top-level variable declaration that should be `as const`, but is `as SomeActualType` instead
+        selector: `:matches(:not(VariableDeclarator) > TSAsExpression, :not(:matches(Program, ExportNamedDeclaration)) > VariableDeclaration > * > TSAsExpression, :matches(Program, ExportNamedDeclaration) > VariableDeclaration > * > TSAsExpression > .expression:not(ObjectExpression:has(Property > ${STRING_LITERAL}.value):not(:has(Property > .value:not(${STRING_LITERAL})))), :matches(Program, ExportNamedDeclaration) > VariableDeclaration > * > TsAsExpression:not(:has(TSTypeReference > Identifier[name=const])) > ObjectExpression.expression:has(Property > ${STRING_LITERAL}.value):not(:has(Property > .value:not(${STRING_LITERAL}))))`,
+        message: 'Avoid `as T`. Consider using a type annotation instead.',
+    },
+    {
+        selector:
+            ':matches(TSUndefinedKeyword, Identifier[name=undefined], UnaryExpression[operator=void]:not(:has(CallExpression.argument)), BinaryExpression[operator=/^===?$/]:has(UnaryExpression.left[operator=typeof]):has(Literal.right[value=undefined]))',
+        message: 'Use `null` instead of `undefined`, `void 0`, or `typeof x === "undefined"`',
     },
     {
         selector: 'ExportNamedDeclaration > VariableDeclaration[kind=let]',
@@ -216,7 +226,7 @@ export default [
             ...tsEslint.configs.recommended?.rules,
             ...tsEslint.configs['recommended-requiring-type-checking']?.rules,
             ...tsEslint.configs.strict?.rules,
-            eqeqeq: 'error',
+            eqeqeq: ['error', 'always', { null: 'never' }],
             'sort-imports': ['error', { allowSeparatedGroups: true }],
             'no-restricted-syntax': ['error', ...RESTRICTED_SYNTAXES],
             'prefer-arrow-callback': 'error',

app/ide-desktop/lib/client/electron-builder-config.ts

@@ -18,7 +18,6 @@ import yargs from 'yargs'
 import * as common from 'enso-common'
 
 import * as paths from './paths.js'
-import * as shared from './shared.js'
 import signArchivesMacOs from './tasks/signArchivesMacOs.js'
 
 import BUILD_INFO from '../../build.json' assert { type: 'json' }
@@ -28,7 +27,9 @@ import BUILD_INFO from '../../build.json' assert { type: 'json' }
  * @see `args` definition below for fields description.
  */
 export interface Arguments {
-    target?: string
+    // This is returned by a third-party library we do not control.
+    // eslint-disable-next-line no-restricted-syntax
+    target?: string | undefined
     iconsDist: string
     guiDist: string
     ideDist: string
@@ -81,7 +82,7 @@ export const args: Arguments = await yargs(process.argv.slice(2))
 export function createElectronBuilderConfig(passedArgs: Arguments): electronBuilder.Configuration {
     return {
         appId: 'org.enso',
-        productName: shared.PRODUCT_NAME,
+        productName: common.PRODUCT_NAME,
         extraMetadata: {
             version: BUILD_INFO.version,
         },
@@ -104,13 +105,16 @@ export function createElectronBuilderConfig(passedArgs: Arguments): electronBuil
         protocols: [
             /** Electron URL protocol scheme definition for deep links to authentication flow pages. */
             {
-                name: `${shared.PRODUCT_NAME} url`,
+                name: `${common.PRODUCT_NAME} url`,
                 schemes: [common.DEEP_LINK_SCHEME],
                 role: 'Editor',
             },
         ],
         mac: {
             // We do not use compression as the build time is huge and file size saving is almost zero.
+            // This type assertion is UNSAFE, and any users MUST verify that
+            // they are passing a valid value to `target`.
+            // eslint-disable-next-line no-restricted-syntax
             target: (passedArgs.target ?? 'dmg') as macOptions.MacOsTargetName,
             icon: `${passedArgs.iconsDist}/icon.icns`,
             category: 'public.app-category.developer-tools',
@@ -223,7 +227,9 @@ export function createElectronBuilderConfig(passedArgs: Arguments): electronBuil
                 console.log('  • Notarizing.')
                 await electronNotarize.notarize({
                     // This will always be defined since we set it at the top of this object.
-                    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+                    // The type-cast is safe because this is only executes
+                    // when `platform === electronBuilder.Platform.MAC`.
+                    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion, no-restricted-syntax
                     appBundleId: (buildOptions as macOptions.MacConfiguration).appId!,
                     appPath: `${appOutDir}/${appName}.app`,
                     appleId: process.env.APPLEID,

app/ide-desktop/lib/client/shared.ts

@@ -1,9 +0,0 @@
-/** @file This module contains metadata about the product and distribution.
- * For example, it contains:
- * - the custom URL protocol scheme definitions.
- *
- * This metadata is used in both the code building the client resources and the packaged code
- * itself. */
-
-/** Name of the product. */
-export const PRODUCT_NAME = 'Enso'

app/ide-desktop/lib/client/src/authentication.ts

@@ -134,8 +134,8 @@ function initOpenUrlListener(window: () => electron.BrowserWindow) {
         event.preventDefault()
         if (parsedUrl.protocol !== `${common.DEEP_LINK_SCHEME}:`) {
             logger.error(`${url} is not a deep link, ignoring.`)
-            return
+        } else {
+            window().webContents.send(ipc.Channel.openDeepLink, url)
         }
-        window().webContents.send(ipc.Channel.openDeepLink, url)
     })
 }

app/ide-desktop/lib/client/src/bin/project-manager.ts

@@ -31,9 +31,7 @@ export function pathOrPanic(args: config.Args): string {
 /** Executes the Project Manager with given arguments. */
 async function exec(args: config.Args, processArgs: string[]) {
     const binPath = pathOrPanic(args)
-    return await execFile(binPath, processArgs).catch(function (err) {
+    return await execFile(binPath, processArgs)
-        throw err
-    })
 }
 
 /** Spawn Project Manager process.
@@ -62,5 +60,7 @@ export function spawn(args: config.Args, processArgs: string[]): childProcess.Ch
 export async function version(args: config.Args) {
     if (args.options.engine.value) {
         return await exec(args, ['--version']).then(t => t.stdout)
+    } else {
+        return
     }
 }

app/ide-desktop/lib/client/src/bin/server.ts

@@ -105,26 +105,26 @@ export class Server {
 
     process(request: http.IncomingMessage, response: http.ServerResponse) {
         const requestUrl = request.url
-        if (requestUrl === undefined) {
+        if (requestUrl == null) {
             logger.error('Request URL is null.')
-            return
+        } else {
-        }
+            const url = requestUrl.split('?')[0]
-        const url = requestUrl.split('?')[0]
+            const resource = url === '/' ? '/index.html' : requestUrl
-        const resource = url === '/' ? '/index.html' : requestUrl
+            const resourceFile = `${this.config.dir}${resource}`
-        const resourceFile = `${this.config.dir}${resource}`
+            fs.readFile(resourceFile, (err, data) => {
-        fs.readFile(resourceFile, (err, data) => {
+                if (err) {
-            if (err) {
+                    logger.error(`Resource '${resource}' not found.`)
-                logger.error(`Resource '${resource}' not found.`)
+                } else {
-            } else {
+                    const contentType = mime.contentType(path.extname(resourceFile))
-                const contentType = mime.contentType(path.extname(resourceFile))
+                    const contentLength = data.length
-                const contentLength = data.length
+                    if (contentType !== false) {
-                if (contentType !== false) {
+                        response.setHeader('Content-Type', contentType)
-                    response.setHeader('Content-Type', contentType)
+                    }
+                    response.setHeader('Content-Length', contentLength)
+                    response.writeHead(HTTP_STATUS_OK)
+                    response.end(data)
                 }
-                response.setHeader('Content-Length', contentLength)
+            })
-                response.writeHead(HTTP_STATUS_OK)
+        }
-                response.end(data)
-            }
-        })
     }
 }

app/ide-desktop/lib/client/src/config/parser.ts

@@ -76,7 +76,7 @@ function printHelp(cfg: PrintHelpConfig) {
 
     for (const [groupName, group] of Object.entries(cfg.args.groups)) {
         let section = sections[groupName]
-        if (section === undefined) {
+        if (section == null) {
             section = new Section()
             sections[groupName] = section
         }
@@ -95,7 +95,7 @@ function printHelp(cfg: PrintHelpConfig) {
             const cmdOption = naming.camelToKebabCase(optionName)
             maxOptionLength = Math.max(maxOptionLength, stringLength(cmdOption))
             const section = sections[option.name]
-            if (section !== undefined) {
+            if (section != null) {
                 section.entries.unshift([cmdOption, option])
             } else {
                 topLevelSection.entries.push([cmdOption, option])
@@ -127,12 +127,12 @@ function printHelp(cfg: PrintHelpConfig) {
                         ? option.description
                         : option.description.slice(0, firstSentenceSplit + 1)
                 const otherSentences = option.description.slice(firstSentence.length)
-                const def =
+                // We explicitly set the default for string options to be `null` in `parseArgs`.
-                    option.defaultDescription ??
+                // eslint-disable-next-line no-restricted-syntax
-                    ((option.default ?? undefined) as string | undefined)
+                const def = option.defaultDescription ?? (option.default as string | null)
                 const defIsEmptyArray = Array.isArray(def) && def.length === 0
                 let defaults = ''
-                if (def !== undefined && def !== '' && !defIsEmptyArray) {
+                if (def != null && def !== '' && !defIsEmptyArray) {
                     defaults = ` Defaults to ${chalk.green(def)}.`
                 }
                 const description = firstSentence + defaults + chalk.gray(otherSentences)
@@ -152,49 +152,50 @@ function wordWrap(str: string, width: number): string[] {
     if (width <= 0) {
         logger.error(`Cannot perform word wrap. The output width is set to '${width}'.`)
         return []
-    }
+    } else {
-    let firstLine = true
+        let firstLine = true
-    let line = ''
+        let line = ''
-    const lines = []
+        const lines = []
-    const inputLines = str.split('\n')
+        const inputLines = str.split('\n')
-    for (const inputLine of inputLines) {
+        for (const inputLine of inputLines) {
-        if (!firstLine) {
+            if (!firstLine) {
-            lines.push(line)
+                lines.push(line)
-            line = ''
+                line = ''
-        }
+            }
-        firstLine = false
+            firstLine = false
-        for (const originalWord of inputLine.split(' ')) {
+            for (const originalWord of inputLine.split(' ')) {
-            let word = originalWord
+                let word = originalWord
-            if (stringLength(word) > width) {
+                if (stringLength(word) > width) {
-                if (line.length > 0) {
+                    if (line.length > 0) {
-                    lines.push(line)
+                        lines.push(line)
-                    line = ''
+                        line = ''
+                    }
+                    const wordChunks = []
+                    while (stringLength(word) > width) {
+                        wordChunks.push(word.slice(0, width))
+                        word = word.slice(width)
+                    }
+                    wordChunks.push(word)
+                    for (const wordChunk of wordChunks) {
+                        lines.push(wordChunk)
+                    }
+                } else {
+                    if (stringLength(line) + stringLength(word) >= width) {
+                        lines.push(line)
+                        line = ''
+                    }
+                    if (line.length !== 0) {
+                        line += ' '
+                    }
+                    line += word
                 }
-                const wordChunks = []
-                while (stringLength(word) > width) {
-                    wordChunks.push(word.slice(0, width))
-                    word = word.slice(width)
-                }
-                wordChunks.push(word)
-                for (const wordChunk of wordChunks) {
-                    lines.push(wordChunk)
-                }
-            } else {
-                if (stringLength(line) + stringLength(word) >= width) {
-                    lines.push(line)
-                    line = ''
-                }
-                if (line.length !== 0) {
-                    line += ' '
-                }
-                line += word
             }
         }
+        if (line) {
+            lines.push(line)
+        }
+        return lines
     }
-    if (line) {
-        lines.push(line)
-    }
-    return lines
 }
 
 // ======================
@@ -205,7 +206,7 @@ export class ChromeOption {
     constructor(public name: string, public value?: string) {}
 
     display(): string {
-        const value = this.value === undefined ? '' : `=${this.value}`
+        const value = this.value == null ? '' : `=${this.value}`
         return `--${this.name}${value}`
     }
 }
@@ -237,20 +238,20 @@ function argvAndChromeOptions(processArgs: string[]): ArgvAndChromeOptions {
     const chromeOptions: ChromeOption[] = []
     for (let i = 0; i < processArgs.length; i++) {
         const processArg = processArgs[i]
-        if (processArg !== undefined) {
+        if (processArg != null) {
-            const match = processArg.match(chromeOptionRegex) ?? undefined
+            const match = processArg.match(chromeOptionRegex)
-            if (match?.[1] !== undefined) {
+            if (match?.[1] != null) {
                 const optionName = match[1]
                 const optionValue = match[2]
-                if (optionValue !== undefined) {
+                if (optionValue != null) {
                     chromeOptions.push(new ChromeOption(optionName, optionValue))
                 } else {
                     const nextArgValue = processArgs[i + 1]
-                    if (nextArgValue !== undefined && !nextArgValue.startsWith('-')) {
+                    if (nextArgValue != null && !nextArgValue.startsWith('-')) {
                         chromeOptions.push(new ChromeOption(optionName, nextArgValue))
                         i++
                     } else {
-                        chromeOptions.push(new ChromeOption(optionName, undefined))
+                        chromeOptions.push(new ChromeOption(optionName))
                     }
                 }
             } else {
@@ -274,19 +275,14 @@ export function parseArgs() {
     const yargsOptions = args
         .optionsRecursive()
         .reduce((opts: Record<string, yargsModule.Options>, option) => {
-            const yargsParam = Object.assign(
-                {},
-                {
-                    ...option,
-                    requiresArg: ['string', 'array'].includes(option.type),
-                    default: undefined,
-                }
-            )
             opts[naming.camelToKebabCase(option.qualifiedName())] = {
-                // Required because ensogl-pack has `defaultDescription`
+                ...option,
-                // defined as `string | null` instead of `string | undefined` like in yargs
+                requiresArg: ['string', 'array'].includes(option.type),
-                ...yargsParam,
+                default: null,
-                defaultDescription: yargsParam.defaultDescription ?? undefined,
+                // Required because yargs defines `defaultDescription`
+                // as `string | undefined`, not `string | null`.
+                // eslint-disable-next-line no-restricted-syntax
+                defaultDescription: option.defaultDescription ?? undefined,
             }
             return opts
         }, {})
@@ -316,7 +312,7 @@ export function parseArgs() {
     interface YargsArgs {
         // We don't control the naming of this third-party API.
         /* eslint-disable @typescript-eslint/naming-convention */
-        [key: string]: string[] | string | undefined
+        [key: string]: string[] | string
         _: string[]
         // Exists only when the `populate--` option is enabled.
         '--'?: string[]
@@ -324,27 +320,29 @@ export function parseArgs() {
         /* eslint-enable @typescript-eslint/naming-convention */
     }
 
-    let parseError: Error | undefined
+    // Required otherwise TypeScript thinks it's always `null`.
+    // eslint-disable-next-line no-restricted-syntax
+    let parseError = null as Error | null
+    // The type assertion is required since `parse` may return a `Promise`
+    // when an async middleware has been registered, but we are not doing that.
+    // eslint-disable-next-line no-restricted-syntax
     const { '--': unexpectedArgs, ...parsedArgs } = optParser.parse(
         argv,
         {},
         // @ts-expect-error Yargs' typings are wrong.
-        // eslint-disable-next-line no-restricted-syntax
         (err: Error | null) => {
-            if (err) {
+            if (err != null) {
                 parseError = err
             }
         }
     ) as YargsArgs
-    // The type assertion above is required since `parse` is defined to potentially return a `Promise`.
-    // This only happens when an async middleware has been registered though.
 
     for (const option of args.optionsRecursive()) {
         const arg = parsedArgs[naming.camelToKebabCase(option.qualifiedName())]
         const isArray = Array.isArray(arg)
         // Yargs parses missing array options as `[undefined]`.
-        const isInvalidArray = isArray && arg.length === 1 && arg[0] === undefined
+        const isInvalidArray = isArray && arg.length === 1 && arg[0] == null
-        if (arg !== undefined && !isInvalidArray) {
+        if (arg != null && !isInvalidArray) {
             option.value = arg
             option.setByUser = true
         }
@@ -386,10 +384,10 @@ export function parseArgs() {
     const helpRequested = args.options.help.value || args.options.helpExtended.value
     if (helpRequested) {
         printHelpAndExit()
-    } else if (parseError !== undefined) {
+    } else if (parseError != null) {
         logger.error(parseError.message)
         printHelpAndExit(1)
-    } else if (unexpectedArgs !== undefined) {
+    } else if (unexpectedArgs != null) {
         const unexpectedArgsString = unexpectedArgs.map(arg => JSON.stringify(arg)).join(' ')
         logger.error(`Unexpected arguments found: '${unexpectedArgsString}'.`)
         printHelpAndExit(1)

app/ide-desktop/lib/client/src/debug.ts

@@ -50,5 +50,7 @@ async function getInfo() {
 /** Print the current system information. */
 export async function printInfo() {
     const info = await getInfo()
+    // This function does not accept `null` as its second parameter.
+    // eslint-disable-next-line no-restricted-syntax
     console.log(JSON.stringify(info, undefined, INDENT_SIZE))
 }

app/ide-desktop/lib/client/src/index.ts

@@ -41,8 +41,8 @@ const INDENT_SIZE = 4
 /** The Electron application. It is responsible for starting all the required services, and
  * displaying and managing the app window. */
 class App {
-    window: electron.BrowserWindow | undefined = undefined
+    window: electron.BrowserWindow | null = null
-    server: server.Server | undefined = undefined
+    server: server.Server | null = null
     args: config.Args = config.CONFIG
     isQuitting = false
 
@@ -194,7 +194,7 @@ class App {
                     frame: useFrame,
                     transparent: false,
                     titleBarStyle: useHiddenInsetTitleBar ? 'hiddenInset' : 'default',
-                    vibrancy: useVibrancy ? 'fullscreen-ui' : undefined,
+                    ...(useVibrancy ? { vibrancy: 'fullscreen-ui' } : {}),
                 }
                 const window = new electron.BrowserWindow(windowPreferences)
                 window.setMenuBarVisibility(false)
@@ -272,7 +272,7 @@ class App {
 
     /** Redirect the web view to `localhost:<port>` to see the served website. */
     loadWindowContent() {
-        if (this.window !== undefined) {
+        if (this.window != null) {
             const urlCfg: Record<string, string> = {}
             for (const option of this.args.optionsRecursive()) {
                 if (option.value !== option.default && option.passToWebApplication) {

app/ide-desktop/lib/client/src/preload.ts

@@ -34,7 +34,7 @@ electron.contextBridge.exposeInMainWorld('enso_lifecycle', {
 
 // Save and load profile data.
 let onProfiles: ((profiles: string[]) => void)[] = []
-let profilesLoaded: string[] | undefined
+let profilesLoaded: string[] | null
 electron.ipcRenderer.on(ipc.Channel.profilesLoaded, (_event, profiles: string[]) => {
     for (const callback of onProfiles) {
         callback(profiles)
@@ -49,7 +49,7 @@ electron.contextBridge.exposeInMainWorld('enso_profiling_data', {
     },
     // Requests any loaded profiling logs.
     loadProfiles: (callback: (profiles: string[]) => void) => {
-        if (profilesLoaded === undefined) {
+        if (profilesLoaded == null) {
             electron.ipcRenderer.send('load-profiles')
             onProfiles.push(callback)
         } else {

app/ide-desktop/lib/client/tasks/computeHashes.cjs

@@ -25,14 +25,14 @@ function getChecksum(path, type) {
     return new Promise(
         // This JSDoc annotation is required for correct types that are also type-safe.
         /** @param {(value: string) => void} resolve - Fulfill the promise with the given value. */
-        function (resolve, reject) {
+        (resolve, reject) => {
             const hash = cryptoModule.createHash(type)
             const input = fs.createReadStream(path)
             input.on('error', reject)
-            input.on('data', function (chunk) {
+            input.on('data', chunk => {
                 hash.update(chunk)
             })
-            input.on('close', function () {
+            input.on('close', () => {
                 resolve(hash.digest('hex'))
             })
         }

app/ide-desktop/lib/common/src/index.ts

@@ -9,3 +9,6 @@
  * For example: the deep link URL
  * `enso://authentication/register?code=...&state=...` uses this scheme. */
 export const DEEP_LINK_SCHEME = 'enso'
+
+/** Name of the product. */
+export const PRODUCT_NAME = 'Enso'

app/ide-desktop/lib/content/esbuild-config.ts

@@ -106,12 +106,16 @@ export async function* filesToCopyProvider(wasmArtifacts: string, assetsPath: st
 /**
  * Generate the builder options.
  */
-export function bundlerOptions(args: Arguments): esbuild.BuildOptions {
+export function bundlerOptions(args: Arguments) {
     const { outputPath, ensoglAppPath, wasmArtifacts, assetsPath } = args
-    return {
+    // This is required to make the `true` properties be typed as `boolean`.
+    // eslint-disable-next-line no-restricted-syntax
+    let trueBoolean = true as boolean
+    const buildOptions = {
+        // Disabling naming convention because these are third-party options.
         /* eslint-disable @typescript-eslint/naming-convention */
         absWorkingDir: THIS_PATH,
-        bundle: true,
+        bundle: trueBoolean,
         entryPoints: [path.resolve(THIS_PATH, 'src', 'index.ts')],
         outdir: outputPath,
         outbase: 'src',
@@ -119,25 +123,23 @@ export function bundlerOptions(args: Arguments): esbuild.BuildOptions {
             esbuildPluginYaml.yamlPlugin({}),
             esbuildPluginNodeModules.NodeModulesPolyfillPlugin(),
             esbuildPluginNodeGlobals.NodeGlobalsPolyfillPlugin({ buffer: true, process: true }),
-            // We do not control naming of third-party options.
             esbuildPluginAlias({ ensogl_app: ensoglAppPath }),
             esbuildPluginTime(),
             esbuildPluginCopy.create(() => filesToCopyProvider(wasmArtifacts, assetsPath)),
         ],
         define: {
-            // Disabling naming convention because these are third-party options.
             GIT_HASH: JSON.stringify(git('rev-parse HEAD')),
             GIT_STATUS: JSON.stringify(git('status --short --porcelain')),
             BUILD_INFO: JSON.stringify(BUILD_INFO),
         },
-        sourcemap: true,
+        sourcemap: trueBoolean,
-        minify: true,
+        minify: trueBoolean,
-        metafile: true,
+        metafile: trueBoolean,
         format: 'esm',
         publicPath: '/assets',
         platform: 'browser',
-        incremental: true,
+        incremental: trueBoolean,
-        color: true,
+        color: trueBoolean,
         logOverride: {
             // Happens in ScalaJS-generated parser (scala-parser.js):
             //    6 │   "fileLevelThis": this
@@ -153,14 +155,18 @@ export function bundlerOptions(args: Arguments): esbuild.BuildOptions {
             'suspicious-boolean-not': 'silent',
         },
         /* eslint-enable @typescript-eslint/naming-convention */
-    }
+    } satisfies esbuild.BuildOptions
+    // The narrower type is required to avoid non-null assertions elsewhere.
+    // The intersection with `esbuild.BuildOptions` is required to allow mutation.
+    const correctlyTypedBuildOptions: esbuild.BuildOptions & typeof buildOptions = buildOptions
+    return correctlyTypedBuildOptions
 }
 
 /** The basic, common settings for the bundler, based on the environment variables.
  *
  * Note that they should be further customized as per the needs of the specific workflow (e.g. watch vs. build).
  */
-export function bundlerOptionsFromEnv(): esbuild.BuildOptions {
+export function bundlerOptionsFromEnv() {
     return bundlerOptions(argumentsFromEnv())
 }
 

app/ide-desktop/lib/content/src/index.ts

@@ -59,9 +59,7 @@ async function checkMinSupportedVersion(config: typeof contentConfig.OPTIONS) {
             )
             if (
                 typeof appConfig === 'object' &&
-                // `typeof x === 'object'` narrows to `object | null`, not `object | undefined`
+                appConfig != null &&
-                // eslint-disable-next-line no-restricted-syntax
-                appConfig !== null &&
                 'minimumSupportedVersion' in appConfig
             ) {
                 const minSupportedVersion = appConfig.minimumSupportedVersion
@@ -88,13 +86,13 @@ function displayDeprecatedVersionDialog() {
         'This version is no longer supported. Please download a new one.'
     )
 
-    const root = document.getElementById('root') ?? undefined
+    const root = document.getElementById('root')
     const versionCheckDiv = document.createElement('div')
     versionCheckDiv.id = 'version-check'
     versionCheckDiv.className = 'auth-info'
     versionCheckDiv.style.display = 'block'
     versionCheckDiv.appendChild(versionCheckText)
-    if (root === undefined) {
+    if (root == null) {
         console.error('Cannot find the root DOM element.')
     } else {
         root.appendChild(versionCheckDiv)

app/ide-desktop/lib/content/src/project_manager.ts

@@ -49,7 +49,7 @@ export class ProjectManager {
             name: name,
             missingComponentAction: action,
         }
-        if (template !== undefined) {
+        if (template != null) {
             Object.assign(params, {
                 projectTemplate: template,
             })

app/ide-desktop/lib/content/start.ts

@@ -9,4 +9,4 @@ const OPTS = bundler.bundleOptions()
 const ROOT = OPTS.outdir
 const ASSETS = ROOT
 await esbuild.build(OPTS)
-await guiServer.start({ root: ROOT, assets: ASSETS })
+await guiServer.start({ root: ROOT, assets: ASSETS ?? null })

app/ide-desktop/lib/content/watch.ts

@@ -11,5 +11,5 @@ const OPTS = bundler.watchOptions(() => {
 await esbuild.build(OPTS)
 const LIVE_SERVER = await guiServer.start({
     root: OPTS.outdir,
-    assets: OPTS.outdir,
+    assets: OPTS.outdir ?? null,
 })

app/ide-desktop/lib/copy-plugin/src/index.mjs

@@ -79,20 +79,21 @@ export function create(filesProvider) {
             }
         })
         build.onLoad({ filter: /.*/, namespace: PLUGIN_NAME }, async () => {
-            if (build.initialOptions.outdir === undefined) {
+            if (build.initialOptions.outdir == null) {
                 console.error('`copy-plugin` requires `outdir` to be specified.')
                 return
-            }
+            } else {
-            let watchFiles = []
+                let watchFiles = []
-            for await (const file of files) {
+                for await (const file of files) {
-                const to = path.join(build.initialOptions.outdir, path.basename(file))
+                    const to = path.join(build.initialOptions.outdir, path.basename(file))
-                await copy(file, to)
+                    await copy(file, to)
-                watchFiles.push(file)
+                    watchFiles.push(file)
-            }
+                }
-            console.log('Copied files.', watchFiles)
+                console.log('Copied files.', watchFiles)
-            return {
+                return {
-                contents: '',
+                    contents: '',
-                watchFiles,
+                    watchFiles,
+                }
             }
         })
         build.onEnd(() => {

app/ide-desktop/lib/dashboard/src/authentication/src/authentication/cognito.ts

@@ -107,6 +107,7 @@ function intoAmplifyErrorOrThrow(error: unknown): AmplifyError {
  * The caller can then handle them via pattern matching on the {@link results.Result} type. */
 export class Cognito {
     constructor(
+        // @ts-expect-error This will be used in a future PR.
         private readonly logger: loggerProvider.Logger,
         private readonly platform: platformModule.Platform,
         amplifyConfig: config.AmplifyConfig

app/ide-desktop/lib/dashboard/src/authentication/src/authentication/config.ts

@@ -130,7 +130,7 @@ export function toNestedAmplifyConfig(config: AmplifyConfig): NestedAmplifyConfi
         userPoolWebClientId: config.userPoolWebClientId,
         oauth: {
             options: {
-                urlOpener: config.urlOpener,
+                ...(config.urlOpener ? { urlOpener: config.urlOpener } : {}),
             },
             domain: config.domain,
             scope: config.scope,

app/ide-desktop/lib/dashboard/src/authentication/src/authentication/listen.tsx

@@ -31,7 +31,7 @@ export enum AuthEvent {
 
 /** Returns `true` if the given `string` is an {@link AuthEvent}. */
 function isAuthEvent(value: string): value is AuthEvent {
-  return Object.values(AuthEvent).includes(value as AuthEvent);
+  return Object.values<string>(AuthEvent).includes(value);
 }
 
 // =================================

app/ide-desktop/lib/dashboard/src/authentication/src/authentication/providers/auth.tsx

@@ -81,8 +81,8 @@ interface AuthContextType {
   signInWithPassword: (email: string, password: string) => Promise<void>;
   /** Session containing the currently authenticated user's authentication information.
    *
-   * If the user has not signed in, the session will be `undefined`. */
+   * If the user has not signed in, the session will be `null`. */
-  session: UserSession | undefined;
+  session: UserSession | null;
 }
 
 // Eslint doesn't like headings.
@@ -94,7 +94,7 @@ interface AuthContextType {
  * An `as ...` cast is unsafe. We use this cast when creating the context. So it appears that the
  * `AuthContextType` can be unsafely (i.e., only partially) initialized as a result of this.
  *
- * So it appears that we should remove the cast and initialize the context as `undefined` instead.
+ * So it appears that we should remove the cast and initialize the context as `null` instead.
  *
  * **However**, initializing a context the existing way is the recommended way to initialize a
  * context in React.  It is safe, for non-obvious reasons. It is safe because the `AuthContext` is
@@ -131,8 +131,8 @@ export function AuthProvider(props: AuthProviderProps) {
   const navigate = router.useNavigate();
   const onAuthenticated = react.useCallback(props.onAuthenticated, []);
   const [initialized, setInitialized] = react.useState(false);
-  const [userSession, setUserSession] = react.useState<UserSession | undefined>(
+  const [userSession, setUserSession] = react.useState<UserSession | null>(
-    undefined
+    null
   );
 
   /** Fetch the JWT access token from the session via the AWS Amplify library.
@@ -144,7 +144,7 @@ export function AuthProvider(props: AuthProviderProps) {
     const fetchSession = async () => {
       if (session.none) {
         setInitialized(true);
-        setUserSession(undefined);
+        setUserSession(null);
       } else {
         const { accessToken, email } = session.val;
 

app/ide-desktop/lib/dashboard/src/authentication/src/authentication/service.tsx

@@ -148,7 +148,7 @@ function loadAmplifyConfig(
   return {
     ...baseConfig,
     ...platformConfig,
-    urlOpener,
+    ...(urlOpener ? { urlOpener } : {}),
   };
 }
 
@@ -225,13 +225,14 @@ function handleAuthResponse(url: string) {
     try {
       /** # Safety
        *
-       * It is safe to disable the `no-unsafe-member-access` and `no-unsafe-call` lints here
+       * It is safe to disable the `no-unsafe-call` lint here
        * because we know that the `Auth` object has the `_handleAuthResponse` method, and we
        * know that it is safe to call it with the `url` argument. There is no way to prove
        * this to the TypeScript compiler, because these methods are intentionally not part of
        * the public AWS Amplify API. */
-      // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-call, @typescript-eslint/no-explicit-any
+      // @ts-expect-error `_handleAuthResponse` is a private method without typings.
-      await (amplify.Auth as any)._handleAuthResponse(url);
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-call
+      await amplify.Auth._handleAuthResponse(url);
     } finally {
       /** Restore the original `window.location.replaceState` function. */
       window.history.replaceState = replaceState;

app/ide-desktop/lib/dashboard/src/authentication/src/components/svg.tsx

@@ -11,13 +11,11 @@
 /** Path data for the SVG icons used in app. */
 export const PATHS = {
   /** Path data for the `@` icon SVG. */
-  at:
+  at: `M16 12a4 4 0 10-8 0 4 4 0 008 0zm0 0v1.5a2.5 2.5 0 005 0V12a9 9 0 10-9 9m4.5-1.206a8.959 \
-    "M16 12a4 4 0 10-8 0 4 4 0 008 0zm0 0v1.5a2.5 2.5 0 005 0V12a9 9 0 10-9 9m4.5-1.206a8.959 " +
+8.959 0 01-4.5 1.207`,
-    "8.959 0 01-4.5 1.207",
   /** Path data for the lock icon SVG. */
-  lock:
+  lock: `M12 15v2m-6 4h12a2 2 0 002-2v-6a2 2 0 00-2-2H6a2 2 0 00-2 2v6a2 2 0 002 2zm10-10V7a4 4 \
-    "M12 15v2m-6 4h12a2 2 0 002-2v-6a2 2 0 00-2-2H6a2 2 0 00-2 2v6a2 2 0 002 2zm10-10V7a4 4 " +
+0 00-8 0v4h8z`,
-    "0 00-8 0v4h8z",
   /** Path data for the "right arrow" icon SVG. */
   rightArrow: "M13 9l3 3m0 0l-3 3m3-3H8m13 0a9 9 0 11-18 0 9 9 0 0118 0z",
   /** Path data for the "create account" icon SVG. */

app/ide-desktop/lib/dashboard/src/authentication/src/index.tsx

@@ -8,6 +8,7 @@
  * included in the final bundle. */
 // It is safe to disable `no-restricted-syntax` because the `PascalCase` naming is required
 // as per the above comment.
+// @ts-expect-error See above comment for why this import is needed.
 // eslint-disable-next-line @typescript-eslint/no-unused-vars, no-restricted-syntax
 import * as React from "react";
 import * as reactDOM from "react-dom/client";

app/ide-desktop/lib/dashboard/src/authentication/src/providers/logger.tsx

@@ -21,6 +21,8 @@ export interface Logger {
 // === LoggerContext ===
 // =====================
 
+/** See {@link AuthContext} for safety details. */
+// eslint-disable-next-line no-restricted-syntax
 const LoggerContext = react.createContext<Logger>({} as Logger);
 
 // ======================

app/ide-desktop/lib/dashboard/src/authentication/src/utils.ts

@@ -29,7 +29,7 @@ export function brand<T extends Brand<string>>(s: NoBrand & Omit<T, '$brand'>):
     // branded type, even if that value is not an instance of the branded type. For example, the
     // string "foo" could be cast to the `UserPoolId` branded type, although this string is clearly
     // not a valid `UserPoolId`. This is acceptable because the branded type is only used to prevent
-    // accidental misuse of values, and not to enforce correctness.  That is, it is up to the
+    // accidental misuse of values, and not to enforce correctness. That is, it is up to the
     // programmer to declare the correct type of a value. After that point, it is up to the branded
     // type to keep that guarantee by preventing accidental misuse of the value.
     // eslint-disable-next-line no-restricted-syntax

app/ide-desktop/lib/icons/src/index.js

@@ -146,67 +146,67 @@ async function genIcons(outputDir) {
         return
     } else {
         console.log(`Generating icons to ${outputDir}`)
-    }
+        console.log('Generating SVG icons.')
+        await fs.mkdir(path.resolve(outputDir, 'svg'), { recursive: true })
+        await fs.mkdir(path.resolve(outputDir, 'png'), { recursive: true })
+        for (const size of sizes) {
+            let name = `icon_${size}x${size}.svg`
+            let logo = new Logo(size, true).generate()
+            await fs.writeFile(`${outputDir}/svg/${name}`, logo)
+        }
 
-    console.log('Generating SVG icons.')
+        /// Please note that this function converts the SVG to PNG
-    await fs.mkdir(path.resolve(outputDir, 'svg'), { recursive: true })
+        /// AND KEEPS THE METADATA INFORMATION ABOUT DPI OF 144.
-    await fs.mkdir(path.resolve(outputDir, 'png'), { recursive: true })
+        /// It is required to properly display png images on MacOS.
-    for (const size of sizes) {
+        /// There is currently no other way in `sharp` to do it.
-        let name = `icon_${size}x${size}.svg`
+        console.log('Generating PNG icons.')
-        let logo = new Logo(size, true).generate()
+        for (const size of sizes) {
-        await fs.writeFile(`${outputDir}/svg/${name}`, logo)
+            let inName = `icon_${size}x${size}.svg`
-    }
+            let outName = `icon_${size}x${size}.png`
+            await sharp(`${outputDir}/svg/${inName}`, { density: MACOS_DPI })
+                .png()
+                .resize({
+                    width: size,
+                    kernel: sharp.kernel.mitchell,
+                })
+                .toFile(`${outputDir}/png/${outName}`)
+        }
 
-    /// Please note that this function converts the SVG to PNG
+        for (const size of sizes.slice(1)) {
-    /// AND KEEPS THE METADATA INFORMATION ABOUT DPI OF 144.
+            let size2 = size / 2
-    /// It is required to properly display png images on MacOS.
+            let inName = `icon_${size}x${size}.svg`
-    /// There is currently no other way in `sharp` to do it.
+            let outName = `icon_${size2}x${size2}@2x.png`
-    console.log('Generating PNG icons.')
+            await sharp(`${outputDir}/svg/${inName}`, { density: MACOS_DPI })
-    for (const size of sizes) {
+                .png()
-        let inName = `icon_${size}x${size}.svg`
+                .resize({
-        let outName = `icon_${size}x${size}.png`
+                    width: size,
-        await sharp(`${outputDir}/svg/${inName}`, { density: MACOS_DPI })
+                    kernel: sharp.kernel.mitchell,
-            .png()
+                })
-            .resize({
+                .toFile(`${outputDir}/png/${outName}`)
-                width: size,
+        }
-                kernel: sharp.kernel.mitchell,
-            })
-            .toFile(`${outputDir}/png/${outName}`)
-    }
 
-    for (const size of sizes.slice(1)) {
+        if (os.platform() === 'darwin') {
-        let size2 = size / 2
+            console.log('Generating ICNS.')
-        let inName = `icon_${size}x${size}.svg`
+            childProcess.execSync(`cp -R ${outputDir}/png ${outputDir}/png.iconset`)
-        let outName = `icon_${size2}x${size2}@2x.png`
+            childProcess.execSync(
-        await sharp(`${outputDir}/svg/${inName}`, { density: MACOS_DPI })
+                `iconutil --convert icns --output ${outputDir}/icon.icns ${outputDir}/png.iconset`
-            .png()
+            )
-            .resize({
+        }
-                width: size,
-                kernel: sharp.kernel.mitchell,
-            })
-            .toFile(`${outputDir}/png/${outName}`)
-    }
 
-    if (os.platform() === 'darwin') {
+        console.log('Generating ICO.')
-        console.log('Generating ICNS.')
+        let files = []
-        childProcess.execSync(`cp -R ${outputDir}/png ${outputDir}/png.iconset`)
+        for (const size of winSizes) {
-        childProcess.execSync(
+            let inName = `icon_${size}x${size}.png`
-            `iconutil --convert icns --output ${outputDir}/icon.icns ${outputDir}/png.iconset`
+            let data = await fs.readFile(`${outputDir}/png/${inName}`)
-        )
+            files.push(data)
-    }
+        }
+        const icoBuffer = await toIco(files)
+        fsSync.writeFileSync(`${outputDir}/icon.ico`, icoBuffer)
 
-    console.log('Generating ICO.')
+        let handle = await fs.open(donePath, 'w')
-    let files = []
+        await handle.close()
-    for (const size of winSizes) {
+        return
-        let inName = `icon_${size}x${size}.png`
-        let data = await fs.readFile(`${outputDir}/png/${inName}`)
-        files.push(data)
     }
-    const icoBuffer = await toIco(files)
-    fsSync.writeFileSync(`${outputDir}/icon.ico`, icoBuffer)
-
-    let handle = await fs.open(donePath, 'w')
-    await handle.close()
 }
 
 /** Main entry function. */

app/ide-desktop/lib/server/src/index.mjs

@@ -22,7 +22,7 @@ export const LIVE_RELOAD_LISTENER_PATH = path.join(DIR_NAME, 'live-reload.js')
 
 /** Start the server.
  *
- * @param {{ root: string; assets?: string; port?: number; }} options - Configuration options for this server.
+ * @param {{ root: string; assets?: string | null; port?: number; }} options - Configuration options for this server.
  */
 export async function start({ root, assets, port }) {
     assets = assets ?? path.join(root, 'assets')

app/ide-desktop/lib/types/enso-gui-server.d.ts

@@ -4,8 +4,9 @@ declare module 'enso-gui-server' {
     export const LIVE_RELOAD_LISTENER_PATH: string
 
     interface StartParams {
-        root?: string
+        // These are not values we explicitly supply
-        assets?: string
+        root: string
+        assets?: string | null
         port?: number
     }
     interface ExectionInfo {

app/ide-desktop/lib/types/modules.d.ts

@@ -48,6 +48,8 @@ declare module 'create-servers' {
     }
     export default function (
         option: CreateServersOptions,
+        // This is a third-party module which we have no control over.
+        // eslint-disable-next-line no-restricted-syntax
         errorHandler: (err: HttpError | undefined) => void
     ): unknown
 }

app/ide-desktop/tsconfig.json

@@ -7,16 +7,18 @@
     "module": "ESNext",
     "moduleResolution": "node",
     "checkJs": true,
-    "noImplicitOverride": true,
+    "strict": true,
-    "noUncheckedIndexedAccess": true,
     "noImplicitAny": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "exactOptionalPropertyTypes": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitOverride": true,
     "removeComments": true,
     "resolveJsonModule": true,
     "sourceMap": true,
     "skipLibCheck": true,
-    "strict": true,
-    "strictNullChecks": true,
-    "strictPropertyInitialization": true,
     "target": "ES2019",
     "jsx": "react-jsx"
   },

app/ide-desktop/utils.ts

@@ -39,6 +39,9 @@ export function requireEnvResolvedPath(name: string) {
  */
 export function requireEnvPathExist(name: string) {
     const value = requireEnv(name)
-    if (fs.existsSync(value)) return value
+    if (fs.existsSync(value)) {
-    else throw Error(`File with path ${value} read from environment variable ${name} is missing.`)
+        return value
+    } else {
+        throw Error(`File with path ${value} read from environment variable ${name} is missing.`)
+    }
 }