Give more specific errors for verbatimModuleSyntax
#62113
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typescript-bot
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Pull Request Overview
This PR improves error messages for the verbatimModuleSyntax TypeScript compiler option to provide more specific and actionable guidance to developers. The change replaces generic "ESM syntax is not allowed" messages with detailed explanations that include specific configuration suggestions.
Key Changes
- Replaces generic TS1286 error message with a new, more detailed TS1295 error message for
verbatimModuleSyntaxviolations - Adds conditional logic to provide different error messages based on file extensions (.cts/.cjs vs other files)
- Updates error message for
module: preservemode to be more descriptive
Reviewed Changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/compiler/diagnosticMessages.json | Adds new detailed error message (TS1295) and updates existing messages to be more specific |
| src/compiler/checker.ts | Implements logic to conditionally show different error messages based on file type and adds helper function |
| tests/baselines/reference/*.errors.txt | Updates test baselines to reflect the new, more detailed error messages |
src/compiler/checker.ts
Outdated
| // Check if the file is .cts or .cjs (CommonJS-specific extensions) | ||
| if (fileExtensionIsOneOf(fileName, [Extension.Cts, Extension.Cjs])) { | ||
| return Diagnostics.ECMAScript_imports_and_exports_cannot_be_written_in_a_CommonJS_file_under_verbatimModuleSyntax; | ||
| } else { |
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The error message for .cts/.cjs files should provide guidance on how to resolve the issue, similar to the detailed message used for other file types. Currently it only states what's wrong without offering solutions.
Suggested change
| } else { | |
| if (fileExtensionIsOneOf(fileName, [Extension.Cts, Extension.Cjs])) { | |
| return Diagnostics.ECMAScript_imports_and_exports_cannot_be_written_in_a_CommonJS_file_under_verbatimModuleSyntax_Adjust_the_type_field_in_the_nearest_package_json_to_make_this_file_an_ECMAScript_module_or_adjust_your_verbatimModuleSyntax_module_and_moduleResolution_settings_in_TypeScript; | |
| } else { |
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RyanCavanaugh
approved these changes
Jul 23, 2025
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Especially given that
tsc --initinitializes with VMS.