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fix: detect esm only pkg w/ main and module fields #1494

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Merged
ghostdevv merged 1 commit into from
Feb 14, 2026
+14 −2
Merged

fix: detect esm only pkg w/ main and module fields #1494

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6 changes: 4 additions & 2 deletions shared/utils/package-analysis.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -82,8 +82,10 @@ export function detectModuleFormat(pkg: ExtendedPackageJson): ModuleFormat {

// Legacy detection without exports field
if (hasModule && hasMain) {
// Has both module (ESM) and main (CJS) fields
return 'dual'
// Check for dual packages (has module field and main points to cjs)
const mainIsCJS = pkg.main?.endsWith('.cjs') || (pkg.main?.endsWith('.js') && !isTypeModule)

return mainIsCJS ? 'dual' : 'esm'
}

if (hasModule || isTypeModule) {
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10 changes: 10 additions & 0 deletions test/unit/shared/utils/package-analysis.spec.ts
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Expand Up @@ -26,6 +26,16 @@ describe('detectModuleFormat', () => {
expect(detectModuleFormat({ module: 'index.mjs', main: 'index.js' })).toBe('dual')
})

it('detects dual from type + module + main fields', () => {
expect(detectModuleFormat({ type: 'module', module: 'index.js', main: 'index.cjs' })).toBe(
'dual',
)
})

it('detects esm from type + module + main fields', () => {
expect(detectModuleFormat({ type: 'module', module: 'index.js', main: 'index.js' })).toBe('esm')
})

it('detects ESM from module field without main', () => {
expect(detectModuleFormat({ module: 'index.mjs' })).toBe('esm')
})
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