Only export @typedef type aliases in modules

[ahejlsberg]

In this PR:

• Only export @typedef type aliases when they occur in modules (i.e. don't export in script files).
• Mark reparsed export assignment nodes as a TypeScript construct such that they're omitted from emitted .js.
• Fix LSP crash by adding missing case for ast.KindJSTypeAliasDeclaration.

Most of the baseline changes result from not marking script files as modules and no longer including invalid export = in emitted .js files.

Fixes #1988.

[jakebailey]

Seems like a net improvement; reading over the diffs we of course still have more JS/JSDoc bugs to address in the future...

[jakebailey]

This seems like a regression, maybe? a.js theoretically is a module because it has module.exports in it, I think, but now we are losing that export and therefore the reference.

[ahejlsberg]

Yeah, that's an oversight. We need to handle the implied export of @typedef in find-all-references.

[jakebailey]

Not your bug but definitely an interesting one.

[ahejlsberg]

This is actually a bug fix I made part of this PR. We now mark reparsed export assignment nodes as a TypeScript construct such that they're properly omitted from the emitted .js.

[jakebailey]

Yes, right, I was just commenting on the remaining diff in the file.

[ahejlsberg]

Got it. Definitely funky!

[Copilot]

Pull Request Overview

This PR fixes the handling of JSDoc @typedef declarations in CommonJS/external modules. Previously, @typedef declarations were being marked as exported during parsing. The fix moves this logic to later stages (declaration emit and binder), ensuring proper scoping and type visibility.

Key Changes

• Removed premature export modifier addition during parsing of @typedef tags
• Added logic in declaration transformer to mark @typedef as exported when in external modules
• Updated binder, checker, and language server to recognize @typedef as implicitly exported in modules
• Fixed export assignment to properly flag TypeScript subtree facts

Reviewed Changes

Copilot reviewed 155 out of 155 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
internal/parser/reparser.go	Removes explicit export modifier from @typedef parsing
internal/transformers/declarations/transform.go	Adds export flag for @typedef in external modules during emission
internal/binder/binder.go	Treats @typedef as having export modifier in modules
internal/checker/emitresolver.go	Makes @typedef visible in external modules
internal/checker/checker.go	Adds @typedef to allowed class member kinds
internal/ls/importTracker.go	Updates export detection to handle @typedef
internal/ast/ast.go	Fixes ExportAssignment subtree facts and adds @typedef to write access declarations
testdata/baselines/*	Updated test baselines showing corrected behavior

[Copilot]

According to custom coding guideline 1000000, the comment on line 73 states '!!! Don't mark typedefs as exported if they are not in a module'. However, the fix now relies on later stages to determine if the typedef is in a module. Consider updating this comment to clarify that export modifiers are added during declaration transformation based on module context, not during parsing.

[Copilot]

This logic for determining whether a JSTypeAliasDeclaration should be exported is duplicated in multiple locations (binder.go line 383, emitresolver.go line 164, importTracker.go line 575). Consider extracting this into a shared helper function to improve maintainability and ensure consistency.

Suggested change

	if ast.IsJSTypeAliasDeclaration(node) && parentIsFile && ast.IsExternalOrCommonJSModule(node.Parent.AsSourceFile()) {
	additions |= ast.ModifierFlagsExport
	}
	return maskModifierFlags(tx.host, node, mask, additions)
	}
	if shouldExportJSTypeAliasDeclaration(node) {
	additions |= ast.ModifierFlagsExport
	}
	return maskModifierFlags(tx.host, node, mask, additions)
	}

[jakebailey]

Is this worth addressing if we are actually copy and pasting this code?

[ahejlsberg]

Yup, done.