feat: support TypeScript 7 for spec preprocessing

cli/CHANGELOG.md

@@ -1,10 +1,14 @@
 <!-- See ../guides/writing-the-cypress-changelog.md for details on writing the changelog. -->
-## 15.18.2
+## 15.19.0
 
 **Performance:**
 
 - Fixed a regression in [14.0.0](#14-0-0) where each message sent from the Cypress server to a Chromium-based browser (including Electron) leaked a small amount of browser memory until the end of the spec. During long, command- or network-heavy specs, this buildup could crash the browser (`We detected that the Chrome Renderer process just crashed`). Fixes [#34226](https://github.com/cypress-io/cypress/issues/34226).
 
+**Features:**
+
+- Added support for TypeScript 7 when preprocessing TypeScript spec and support files, and the component testing setup wizard now accepts TypeScript 7. Addresses [#34258](https://github.com/cypress-io/cypress/issues/34258). Addressed in [#34277](https://github.com/cypress-io/cypress/pull/34277).
+
 **Bugfixes:**
 
 - Fixed an issue where, on Windows, enhancing a test failure stack could throw a secondary `TypeError: Cannot read properties of undefined (reading 'replaceAll')` and mask the original error. Fixed in [#34252](https://github.com/cypress-io/cypress/pull/34252).

npm/webpack-batteries-included-preprocessor/index.ts

@@ -33,6 +33,40 @@ class TypeScriptNotFoundError extends Error {
 
 const typescriptExtensionRegex = /\.m?tsx?$/
 
+// Shared by the JS spec rule and the TypeScript 7+ rule (TS 7 has no compiler
+// API for ts-loader). `typescript: true` adds preset-typescript.
+const getBabelLoaderOptions = ({ typescript = false }: { typescript?: boolean } = {}) => {
+  return {
+    plugins: [
+      // Legacy decorators + metadata, ordered before class-properties, to keep
+      // emitDecoratorMetadata parity with ts-loader.
+      ...(typescript ? [
+        require.resolve('babel-plugin-transform-typescript-metadata'),
+        [require.resolve('@babel/plugin-proposal-decorators'), { version: 'legacy' }],
+      ] : []),
+      ...[
+        'babel-plugin-add-module-exports',
+        '@babel/plugin-transform-class-properties',
+        '@babel/plugin-transform-object-rest-spread',
+      ].map((plugin) => require.resolve(plugin)),
+      [require.resolve('@babel/plugin-transform-runtime'), {
+        absoluteRuntime: path.dirname(require.resolve('@babel/runtime/package')),
+      }],
+    ],
+    presets: [
+      // the chrome version should be synced with
+      // packages/web-config/webpack.config.base.ts and
+      // packages/server/lib/browsers/chrome.ts
+      [require.resolve('@babel/preset-env'), { modules: 'commonjs', targets: { 'chrome': '64' } }],
+      require.resolve('@babel/preset-react'),
+      // Last preset runs first: strip types before preset-env/react.
+      ...(typescript ? [require.resolve('@babel/preset-typescript')] : []),
+    ],
+    configFile: false,
+    babelrc: false,
+  }
+}
+
 const hasTsLoader = (rules: any[]) => {
   return rules.some((rule) => {
     if (!rule.use || !Array.isArray(rule.use)) return false
@@ -94,51 +128,67 @@ const addTypeScriptConfig = (file: { filePath: string }, options: {
     return options
   }
 
-  // tsx parses the moduleResolution default to node10 as well as moduleResolution="node" to node10
-  // ts-loader struggles to validate the node10 moduleResolution option depending on the version of typescript used,
-  // so we set it to node which is the same as node 10. @see https://www.typescriptlang.org/tsconfig/#moduleResolution.
-  if (configFile?.config?.compilerOptions?.moduleResolution === 'node10') {
-    configFile.config.compilerOptions.moduleResolution = 'node'
-  }
-
   const tsVersion = webpackPreprocessor.getResolvedTypescriptVersion(typeof typeScriptPath === 'string' ? typeScriptPath : undefined)
 
   let isLessThanTs6
   let isGreaterThanOrEqualToTs6
+  let isGreaterThanOrEqualToTs7
 
   if (tsVersion && semver.valid(tsVersion)) {
     isLessThanTs6 = semver.lt(tsVersion, '6.0.0-0')
     isGreaterThanOrEqualToTs6 = !isLessThanTs6
+    isGreaterThanOrEqualToTs7 = semver.gte(tsVersion, '7.0.0-0')
+  }
+
+  if (isGreaterThanOrEqualToTs7) {
+    // TypeScript 7 ships no JavaScript compiler API, so ts-loader crashes.
+    // Transpile with Babel instead, matching the prior transpile-only behavior.
+    webpackOptions.module.rules.push({
+      test: typescriptExtensionRegex,
+      exclude: [/node_modules/],
+      use: [
+        {
+          loader: require.resolve('babel-loader'),
+          options: getBabelLoaderOptions({ typescript: true }),
+        },
+      ],
+    })
+  } else {
+    // tsx parses the moduleResolution default to node10 as well as moduleResolution="node" to node10
+    // ts-loader struggles to validate the node10 moduleResolution option depending on the version of typescript used,
+    // so we set it to node which is the same as node 10. @see https://www.typescriptlang.org/tsconfig/#moduleResolution.
+    if (configFile?.config?.compilerOptions?.moduleResolution === 'node10') {
+      configFile.config.compilerOptions.moduleResolution = 'node'
+    }
+
+    webpackOptions.module.rules.push({
+      test: typescriptExtensionRegex,
+      exclude: [/node_modules/],
+      use: [
+        {
+          loader: require.resolve('ts-loader'),
+          options: {
+            ...(isGreaterThanOrEqualToTs6 ? {
+              configFile: configFile?.path,
+            } : {}),
+            compiler: typeScriptPath,
+            ...(isLessThanTs6 ? {
+              compilerOptions: configFile?.config?.compilerOptions,
+            } : {}),
+            logLevel: 'error',
+            silent: true,
+            transpileOnly: true,
+          },
+        },
+      ],
+    })
   }
 
-  // Use the v3 plugin for TS < 6 to remain passive; TS 6+ uses v4, which
-  // tolerates the missing-baseUrl shape recommended by TypeScript 6+.
+  // v3 plugin for TS < 6; TS 6+ uses v4, which tolerates the missing-baseUrl shape.
   const TsconfigPathsPlugin = isLessThanTs6
     ? require('tsconfig-paths-webpack-plugin-v3')
     : require('tsconfig-paths-webpack-plugin')
 
-  webpackOptions.module.rules.push({
-    test: typescriptExtensionRegex,
-    exclude: [/node_modules/],
-    use: [
-      {
-        loader: require.resolve('ts-loader'),
-        options: {
-          ...(isGreaterThanOrEqualToTs6 ? {
-            configFile: configFile?.path,
-          } : {}),
-          compiler: typeScriptPath,
-          ...(isLessThanTs6 ? {
-            compilerOptions: configFile?.config?.compilerOptions,
-          } : {}),
-          logLevel: 'error',
-          silent: true,
-          transpileOnly: true,
-        },
-      },
-    ],
-  })
-
   webpackOptions.resolve.extensions = webpackOptions.resolve.extensions.concat(['.ts', '.tsx'])
   webpackOptions.resolve.extensionAlias = webpackOptions.resolve.extensionAlias || { '.js': ['.ts', '.js'], '.mjs': ['.mts', '.mjs'] }
 
@@ -179,27 +229,7 @@ const getDefaultWebpackOptions = () => {
         type: 'javascript/auto',
         use: [{
           loader: require.resolve('babel-loader'),
-          options: {
-            plugins: [
-              ...[
-                'babel-plugin-add-module-exports',
-                '@babel/plugin-transform-class-properties',
-                '@babel/plugin-transform-object-rest-spread',
-              ].map((plugin) => require.resolve(plugin)),
-              [require.resolve('@babel/plugin-transform-runtime'), {
-                absoluteRuntime: path.dirname(require.resolve('@babel/runtime/package')),
-              }],
-            ],
-            presets: [
-              // the chrome version should be synced with
-              // packages/web-config/webpack.config.base.ts and
-              // packages/server/lib/browsers/chrome.ts
-              [require.resolve('@babel/preset-env'), { modules: 'commonjs', targets: { 'chrome': '64' } }],
-              require.resolve('@babel/preset-react'),
-            ],
-            configFile: false,
-            babelrc: false,
-          },
+          options: getBabelLoaderOptions(),
         }],
       }, {
         test: /\.coffee$/,

npm/webpack-batteries-included-preprocessor/package.json

@@ -15,14 +15,17 @@
   },
   "dependencies": {
     "@babel/core": "^7.28.0",
+    "@babel/plugin-proposal-decorators": "^7.28.0",
     "@babel/plugin-transform-class-properties": "^7.27.1",
     "@babel/plugin-transform-object-rest-spread": "^7.28.0",
     "@babel/plugin-transform-runtime": "^7.28.0",
     "@babel/preset-env": "^7.28.0",
     "@babel/preset-react": "^7.27.1",
+    "@babel/preset-typescript": "^7.27.1",
     "@babel/runtime": "^7.28.2",
     "babel-loader": "^10.0.0",
     "babel-plugin-add-module-exports": "^1.0.2",
+    "babel-plugin-transform-typescript-metadata": "^0.4.0",
     "buffer": "^6.0.3",
     "coffee-loader": "^4.0.0",
     "coffeescript": "2.6.0",
@@ -48,8 +51,10 @@
     "globals": "^15.12.0",
     "jiti": "^2.4.2",
     "react": "^16.13.1",
+    "reflect-metadata": "^0.2.2",
     "typescript": "^6.0.0",
     "typescript-v5": "npm:typescript@~5.4.5",
+    "typescript-v7": "npm:typescript@^7.0.0",
     "vitest": "^3.2.4"
   },
   "peerDependencies": {

npm/webpack-batteries-included-preprocessor/test/e2e/features.spec.ts

@@ -129,4 +129,25 @@ describe('webpack-batteries-included-preprocessor features', () => {
       }
     })
   })
+
+  describe('with typescript 7 (native compiler)', () => {
+    const options = { typescript: require.resolve('typescript-v7') }
+
+    it('handles typescript (and tsconfig paths) via babel', async () => {
+      await runAndEval('ts_spec.ts', { ...options })
+    })
+
+    it('handles tsx via babel', async () => {
+      await runAndEval('tsx_spec.tsx', { ...options })
+    })
+
+    it('handles importing .ts and .tsx via babel', async () => {
+      await runAndEval('typescript_imports_spec.js', { ...options })
+    })
+
+    // Babel must still emit decorator metadata for TypeScript 7, as ts-loader did.
+    it('emits decorator metadata (emitDecoratorMetadata parity) via babel', async () => {
+      await runAndEval('typescript_decorators_spec.ts', { ...options })
+    })
+  })
 })

npm/webpack-batteries-included-preprocessor/test/fixtures/typescript_decorators_spec.ts

@@ -0,0 +1,18 @@
+import 'reflect-metadata'
+import { expect } from 'chai'
+
+class Dep {}
+
+function Injectable () {
+  return (_target: any) => {}
+}
+
+@Injectable()
+class Service {
+  constructor (public dep: Dep) {}
+}
+
+// The constructor param type must be emitted as runtime metadata.
+const paramTypes = Reflect.getMetadata('design:paramtypes', Service) as unknown[]
+
+expect(paramTypes).to.deep.equal([Dep])

npm/webpack-batteries-included-preprocessor/test/unit/index.spec.ts

@@ -303,5 +303,81 @@ describe('webpack-batteries-included-preprocessor', () => {
         expect(tsLoader.options.compilerOptions).toBeUndefined()
       })
     })
+
+    describe('with typescript 7 or newer', () => {
+      const fixtureTsconfigPath = path.resolve(__dirname, '../../test/fixtures/tsconfig.json')
+
+      const entryName = (entry: unknown) => (Array.isArray(entry) ? entry[0] : entry) as string
+
+      it.each(['7.0.0', '7.0.2', '7.1.0-beta', '8.0.0'] as const)(
+        'when resolved version is %s, uses babel-loader with @babel/preset-typescript instead of ts-loader',
+        (resolvedVersion) => {
+          vi.mocked(webpackPreprocessor.getResolvedTypescriptVersion).mockReturnValue(resolvedVersion)
+
+          vi.mocked(getTsConfig).getTsconfig.mockReturnValue({
+            config: {
+              compilerOptions: {
+                module: 'ESNext',
+                moduleResolution: 'Bundler',
+              },
+            },
+            path: fixtureTsconfigPath,
+          })
+
+          const preprocessorCB = preprocessor({
+            typescript: true,
+            webpackOptions,
+          })
+
+          preprocessorCB({
+            filePath: 'foo.ts',
+            outputPath: '.js',
+          } as any)
+
+          const rule = webpackOptions.module.rules[0]
+          const loader = rule.use[0]
+          const presets = loader.options.presets.map(entryName)
+          const plugins = loader.options.plugins.map(entryName)
+
+          expect(rule.test.toString()).toEqual(/\.m?tsx?$/.toString())
+          expect(loader.loader).toContain('babel-loader')
+          expect(loader.loader).not.toContain('ts-loader')
+          expect(presets.some((p: string) => p.includes('preset-typescript'))).toBe(true)
+          // emitDecoratorMetadata parity: metadata transform must precede the decorators transform
+          const metadataIdx = plugins.findIndex((p: string) => p.includes('babel-plugin-transform-typescript-metadata'))
+          const decoratorsIdx = plugins.findIndex((p: string) => p.includes('plugin-proposal-decorators'))
+
+          expect(metadataIdx).toBeGreaterThanOrEqual(0)
+          expect(decoratorsIdx).toBeGreaterThan(metadataIdx)
+        },
+      )
+
+      it('still registers the tsconfig paths plugin so path aliases resolve', () => {
+        vi.mocked(webpackPreprocessor.getResolvedTypescriptVersion).mockReturnValue('7.0.2')
+
+        vi.mocked(getTsConfig).getTsconfig.mockReturnValue({
+          config: {
+            compilerOptions: {
+              module: 'ESNext',
+              moduleResolution: 'Bundler',
+            },
+          },
+          path: fixtureTsconfigPath,
+        })
+
+        const preprocessorCB = preprocessor({
+          typescript: true,
+          webpackOptions,
+        })
+
+        preprocessorCB({
+          filePath: 'foo.ts',
+          outputPath: '.js',
+        } as any)
+
+        expect(webpackOptions.resolve.extensions).toEqual(expect.arrayContaining(['.ts', '.tsx']))
+        expect(webpackOptions.resolve.plugins).toHaveLength(1)
+      })
+    })
   })
 })

packages/scaffold-config/src/dependencies.ts

@@ -40,7 +40,7 @@ export const WIZARD_DEPENDENCY_TYPESCRIPT = {
   package: 'typescript',
   installer: 'typescript',
   description: 'TypeScript is a language for application-scale JavaScript',
-  minVersion: '^5.0.0 || ^6.0.0',
+  minVersion: '^5.0.0 || ^6.0.0 || ^7.0.0',
 } as const
 
 export const WIZARD_DEPENDENCY_VITE = {

packages/scaffold-config/test/dependencies.spec.ts

@@ -19,6 +19,11 @@ describe('WIZARD_DEPENDENCY_TYPESCRIPT', () => {
     expect(satisfies('6.0.2')).toBe(true)
   })
 
+  it('accepts TypeScript 7.x per minVersion', () => {
+    expect(satisfies('7.0.0')).toBe(true)
+    expect(satisfies('7.0.2')).toBe(true)
+  })
+
   it('rejects TypeScript below 5', () => {
     expect(satisfies('4.9.5')).toBe(false)
   })

system-tests/projects/ts-proj-7/cypress.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'cypress'
+
+export default defineConfig({
+  e2e: {
+    supportFile: false,
+  },
+})

system-tests/projects/ts-proj-7/cypress/e2e/app.cy.ts

@@ -0,0 +1,9 @@
+import { add } from './math'
+
+type Nums = { a: number, b: number }
+
+it('compiles and runs a TypeScript spec under typescript@7', () => {
+  const nums: Nums = { a: 1, b: 2 }
+
+  expect(add(nums.a, nums.b)).to.eq(3)
+})

system-tests/projects/ts-proj-7/cypress/e2e/decorators.cy.ts

@@ -0,0 +1,19 @@
+import 'reflect-metadata'
+
+class Dep {}
+
+function Injectable () {
+  return (_target: any) => {}
+}
+
+@Injectable()
+class Service {
+  constructor (public dep: Dep) {}
+}
+
+// Babel must still emit decorator metadata for typescript@7.
+it('preserves emitDecoratorMetadata under typescript@7', () => {
+  const paramTypes = Reflect.getMetadata('design:paramtypes', Service)
+
+  expect(paramTypes).to.deep.eq([Dep])
+})