feat(toExports): add declaration option to generate exports for declaration files

[8ctavio]

Resolves #472

• Add a new options parameter to toExports. As mentioned in the issue, other parameters could be incorporated to options in the future.
• Add ToExportOptions.declaration to read from imports' typeFrom if provided.
• In toImportModule, use typeFrom instead of from if provided and options.declaration is true. This causes toExports to use typeFrom as the specifier for generated exports.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.67%. Comparing base (a4a5e0a) to head (7d752b0).
⚠️ Report is 134 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #477      +/-   ##
==========================================
- Coverage   98.73%   97.67%   -1.06%     
==========================================
  Files          14       15       +1     
  Lines        1817     1463     -354     
  Branches      374      479     +105     
==========================================
- Hits         1794     1429     -365     
- Misses         23       34      +11     

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[antfu]

Suggested change

	).toMatchInlineSnapshot(`"export { foo } from 'pkg/dts';"`)
	).toMatchInlineSnapshot(`"export type { foo } from 'pkg/dts';"`)

Should it be like this as well?

[8ctavio]

It seems that toExports does not currently emmit export type, and typeFrom is only concerned with the specifier; but since declaration: true is supposed to be used for declaration files, generating type-only exports with the export type {} from syntax may also be supported.

Imports, however, are "marked" as type-only with the Import.type option. Perhaps when includeType and declaration are set to true, toExports should use export type {} for type-only imports (those with type: true). For reference, generateTypeDeclarations uses toTypeReExports for type-only imports.