Deprecate esModuleInterop and allowSyntheticDefaultImports (default to true)

[Andrew Branch (andrewbranch)]

Closes#62529

[Copilot]

Pull Request Overview

This PR implements default esModuleInterop and allowSyntheticDefaultImports behavior while deprecating explicit false settings. The changes update TypeScript's module interoperability to behave as if these options are always enabled, which affects how import statements are transpiled to CommonJS.

Key changes:

• Updates module import transpilation to use import helpers by default
• Adds deprecation warnings for explicit false settings of esModuleInterop and allowSyntheticDefaultImports
• Modifies type resolution for dynamic imports to include default export wrappers

Reviewed Changes

Copilot reviewed 300 out of 459 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/baselines/reference/moduleExportAliasImported.types	Updates type expectations for dynamic imports to include default wrapper
tests/baselines/reference/moduleAugmentationDoesNamespaceEnumMergeOfReexport.js	Adds import helper functions for namespace imports
tests/baselines/reference/mergedDeclarations7.js	Includes __importStar helper for require() calls
tests/baselines/reference/legacyNodeModulesExportsSpecifierGenerationConditions.js	Wraps dynamic imports with __importStar helper
tests/baselines/reference/keyofModuleObjectHasCorrectKeys.js	Uses __importStar for namespace imports
tests/baselines/reference/jsxViaImport.2.js	Adds __importDefault helper for default imports
tests/baselines/reference/jsxSpreadFirstUnionNoErrors.js	Uses __importDefault for React import
Multiple JSX test files	Consistently use __importStar for React namespace imports
Multiple import test files	Add import helper functions and update error messages for deprecated options
tests/baselines/reference/importAttributes9.*	Updates dynamic import type resolution

[Jake Bailey (jakebailey)]

TypeScript Bot (@typescript-bot) run dt

[TypeScript Bot (typescript-bot)]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
run dt	✅ Started	👀 Results

[Jake Bailey (jakebailey)]

o7

[Andrew Branch (andrewbranch)]

I'll fix anything that turns up on DT tomorrow

[TypeScript Bot (typescript-bot)]

Hey Jake Bailey (@jakebailey), the results of running the DT tests are ready.

There were interesting changes:

Changes are too big to display here, please check the log.

You can check the log here.

[Jake Bailey (jakebailey)]

Uh oh

[LukeAbby]

Heads up, because there's no issue with "Breaking Change" the only way I discovered this was by having the error and finding this PR. Not sure how big of a deal that is though.