[Asil Doğan Gümüş (asilgumus)]

Problem

When a .tsx file is a script file (non-module) — i.e. it contains no top-level import/export (or import.meta), and it is not forced to be a module — the checker still resolves the (compiler-injected) implicit JSX runtime import (<jsxImportSource>/jsx-runtime) that TypeScript adds to every .tsx file with an automatic/implicit JSX factory. That resolution fails, and the checker reported:

error TS2875: This JSX tag requires the module path 'solid-js/jsx-runtime' to exist, but none could be found.
Make sure you have types for the appropriate package installed.

For example, with // @jsx: react-jsx, // @jsxImportSource: solid-js, // @moduleDetection: legacy and even with the package's type declarations present, a file containing just:

const x = <div />;

reports TS2875, which claims the package or its types are missing. The real reason is that the file is a script and script files cannot import modules, so the implicit jsx-runtime import cannot be resolved at all. Adding export {} (as reported in #64438) resolves it. Fixes #64438.

Root cause

getJsxNamespaceContainerForImplicitImport in tsc/internal/checker/jsx.go resolves the implicit JSX runtime import and, on failure, always reports TS2875 — without taking the importing file's module-ness into account. Under moduleDetection: legacy (or when JSX does not force module-ness), a script file will never be able to resolve that import, so TS2875's "Make sure you have types for the appropriate package installed" advice was wrong/misleading.

Fix

When the implicit JSX runtime import cannot be resolved and the importing file is not a module (!ast.IsExternalOrCommonJSModule(file)), the checker now reports a new, targeted diagnostic TS2884:

This JSX tag requires the module 'solid-js/jsx-runtime', which cannot be resolved in a script file. Add an empty 'export {}' statement to make this file a module.

Behavior summary:

Scenario	Before	After
Script file, runtime unresolvable/missing	TS2875 (misleading: "install types")	TS2884 (explains the real issue and the fix)
Module file, runtime missing	TS2875	TS2875 (unchanged)
Script file, runtime resolvable	no error	no error (unchanged — resolution still succeeds before any error is chosen)

New message source is tsc/internal/diagnosticMessages.json; diagnostics_generated.go, diagnosticMessages.generated.json, and loc_generated.go are regenerated with npx hereby generate:diagnostics.

Tests / baselines

• New: tsc/testdata/tests/cases/compiler/jsxScriptFile.tsx — script file with jsxImportSource and no resolvable runtime → expects TS2884 + TS7026.
• New: tsc/testdata/tests/cases/compiler/jsxImportSourceModuleMissing.tsx — module file with missing runtime → expects the unchanged TS2875 (guards the existing behavior).
• New: tsc/testdata/tests/cases/compiler/jsxScriptFileResolvableImportSource.tsx — script file whose runtime does resolve → expects no errors (guards against over-reporting).
• Regenerated reference baselines; the only pre-existing baselines that changed are commentsOnJSXExpressionsArePreserved(jsx=react-jsx,module=commonjs,moduledetection=legacy).errors.txt and the react-jsxdev sibling (script files under legacy module detection now report TS2884 instead of TS2875).

go test ./internal/testrunner passes locally with these baselines.

Verification

Built tsc.exe from source; before/after:

// script file, jsx: react-jsx, jsxImportSource: solid-js, moduleDetection: legacy
- error TS2875: This JSX tag requires the module path 'solid-js/jsx-runtime' to exist, but none could be found...
+ error TS2884: This JSX tag requires the module 'solid-js/jsx-runtime', which cannot be resolved in a script file. Add an empty 'export {}' statement to make this file a module.

// same file after adding 'export {}'. It is now a module:
→ TS2875 appears again, now with the accurate "package/types missing" info for module files.

// script file with a resolvable runtime:
→ still no errors.

Note: there are other open PRs for this issue; this one targets the current main (native Go compiler) and follows its diagnostic-generation flow.

🤖 Generated with Claude Code

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[Copilot]

🟡 Changes recommended

The JSX diagnostic incorrectly attributes missing-runtime resolution failures to script status and recommends module conversion that does not fix the absent dependency.

1 open issue

• Don't attribute missing JSX runtime to script status · New

1 file not reviewed

• tsc/internal/diagnostics/diagnostics_generated.go: Generated file

What changed in this PR

This PR aims to improve the native TypeScript compiler’s diagnostic for unresolved JSX runtime imports in script files, addressing #64438 with guidance to add export {}.

Changes:

• Selects the new TS2884 diagnostic for script files while retaining TS2875 for modules.
• Adds the diagnostic definition and generated message entries.
• Adds three compiler tests and baselines covering missing and resolvable runtimes, and updates two existing diagnostic baselines.

File	Description
tsc/​testdata/​tests/​cases/​compiler/​jsxScriptFileResolvableImportSource.tsx	Tests a script with available runtime declarations.
tsc/​testdata/​tests/​cases/​compiler/​jsxScriptFile.tsx	Tests a script with a missing runtime.
tsc/​testdata/​tests/​cases/​compiler/​jsxImportSourceModuleMissing.tsx	Tests a module with a missing runtime.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFileResolvableImportSource.types	Records resolvable-script types.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFileResolvableImportSource.symbols	Records resolved JSX symbols.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFileResolvableImportSource.js	Records resolvable-script emit.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.types	Records missing-runtime script types.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.symbols	Records missing-runtime script symbols.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.js	Records missing-runtime script emit.
tsc/​testdata/​baselines/​reference/​compiler/​jsxScriptFile.errors.txt	Expects TS2884 and TS7026.
tsc/​testdata/​baselines/​reference/​compiler/​jsxImportSourceModuleMissing.types	Records missing-runtime module types.
tsc/​testdata/​baselines/​reference/​compiler/​jsxImportSourceModuleMissing.symbols	Records missing-runtime module symbols.
tsc/​testdata/​baselines/​reference/​compiler/​jsxImportSourceModuleMissing.js	Records module emit and runtime import.
tsc/​testdata/​baselines/​reference/​compiler/​jsxImportSourceModuleMissing.errors.txt	Preserves TS2875 and TS7026 expectations.
tsc/​testdata/​baselines/​reference/​compiler/​commentsOnJSXExpressionsArePreserved(jsx=react-jsxdev,module=commonjs,moduledetection=legacy).errors.txt	Updates development-runtime errors to TS2884.
tsc/​testdata/​baselines/​reference/​compiler/​commentsOnJSXExpressionsArePreserved(jsx=react-jsx,module=commonjs,moduledetection=legacy).errors.txt	Updates automatic-runtime errors to TS2884.
tsc/​internal/​diagnostics/​diagnostics_generated.go	Registers the generated TS2884 message.
tsc/​internal/​diagnostics/​diagnosticMessages.json	Defines TS2884 and its guidance.
tsc/​internal/​diagnostics/​diagnosticMessages.generated.json	Adds the generated message entry.
tsc/​internal/​checker/​jsx.go	Selects the diagnostic based on module status.

_{Review effort: Balanced}

[Jake Bailey (jakebailey)]

Why did you choose to fix this specific issue?