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Do not assign named exports into existing default export #3494

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9ff1aac
fix: do not modify existing default export
CertainLach Sep 25, 2025
3e846db
fix: ensure typeof exports, drop named export reassignment
CertainLach Sep 25, 2025
3334b31
fix: remove unused namedExports logic
CertainLach Sep 25, 2025
91fd841
test: reduce default export example
CertainLach Sep 25, 2025
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167 changes: 105 additions & 62 deletions packages/plugin-vite/src/plugins/patches/commonjs.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -189,19 +189,14 @@ export function cjsPlugin(
);
}

const exportNamed = new Map<string, string>();

const idExports: types.ExportSpecifier[] = [];
for (const name of exported) {
if (name === "default") {
exportNamed.set(name, name);
continue;
}

const id = path.scope.generateUidIdentifier(name);

exportNamed.set(id.name, name);

path.pushContainer(
"body",
t.variableDeclaration(
Expand All @@ -227,94 +222,141 @@ export function cjsPlugin(
);
}

if (exportNamed.size > 0 || exportedNs.size > 0 || hasEsModule) {
if (exported.size > 0 || exportedNs.size > 0 || hasEsModule) {
const id = path.scope.generateUidIdentifier("__default");

path.pushContainer(
"body",
t.variableDeclaration("const", [
t.variableDeclaration("let", [
t.variableDeclarator(
id,
),
]),
);

path.pushContainer(
"body",
t.ifStatement(
t.logicalExpression(
"&&",
t.logicalExpression(
"??",
t.memberExpression(
"&&",
t.binaryExpression(
"===",
t.unaryExpression("typeof", t.identifier("exports")),
t.stringLiteral("object"),
),
t.binaryExpression(
"!==",
t.identifier("exports"),
t.identifier("default"),
t.nullLiteral(),
),
),
t.binaryExpression(
"in",
t.stringLiteral("default"),
t.identifier("exports"),
),
),
]),
);

for (const [local, exported] of exportNamed.entries()) {
if (exported === "default") continue;

path.pushContainer(
"body",
t.expressionStatement(
t.assignmentExpression(
"=",
t.memberExpression(id, t.identifier(exported)),
t.identifier(local),
t.blockStatement([
t.expressionStatement(
t.assignmentExpression(
"=",
id,
t.memberExpression(
t.identifier("exports"),
t.identifier("default"),
),
),
),
),
);
}
]),
t.blockStatement([
t.expressionStatement(
t.assignmentExpression("=", id, t.identifier("exports")),
),
]),
),
);

for (let i = 0; i < mappedNs.length; i++) {
const mapped = mappedNs[i];

const key = path.scope.generateUid("k");
path.pushContainer(
"body",
t.forInStatement(
t.variableDeclaration("var", [
t.variableDeclarator(t.identifier(key)),
]),
t.identifier(mapped),
t.ifStatement(
t.ifStatement(
t.logicalExpression(
"&&",
t.logicalExpression(
"&&",
t.binaryExpression(
"===",
t.unaryExpression("typeof", t.identifier("exports")),
t.stringLiteral("object"),
),
t.binaryExpression(
"!==",
t.identifier("exports"),
t.nullLiteral(),
),
),
t.unaryExpression(
"!",
t.binaryExpression(
"in",
t.stringLiteral("default"),
t.identifier("exports"),
),
),
),
t.forInStatement(
t.variableDeclaration("var", [
t.variableDeclarator(t.identifier(key)),
]),
t.identifier(mapped),
t.ifStatement(
t.logicalExpression(
"&&",
t.binaryExpression(
"!==",
t.identifier(key),
t.stringLiteral("default"),
),
t.binaryExpression(
"!==",
t.identifier(key),
t.stringLiteral("__esModule"),
t.logicalExpression(
"&&",
t.binaryExpression(
"!==",
t.identifier(key),
t.stringLiteral("default"),
),
t.binaryExpression(
"!==",
t.identifier(key),
t.stringLiteral("__esModule"),
),
),
),
t.callExpression(
t.memberExpression(
t.callExpression(
t.memberExpression(
t.memberExpression(
t.identifier("Object"),
t.identifier("prototype"),
t.memberExpression(
t.identifier("Object"),
t.identifier("prototype"),
),
t.identifier("hasOwnProperty"),
),
t.identifier("hasOwnProperty"),
t.identifier("call"),
),
t.identifier("call"),
[t.identifier(mapped), t.identifier(key)],
),
[t.identifier(mapped), t.identifier(key)],
),
),
t.expressionStatement(
t.assignmentExpression(
"=",
t.memberExpression(
t.cloneNode(id, true),
t.identifier(key),
true,
),
t.memberExpression(
t.identifier(mapped),
t.identifier(key),
true,
t.expressionStatement(
t.assignmentExpression(
"=",
t.memberExpression(
t.cloneNode(id, true),
t.identifier(key),
true,
),
t.memberExpression(
t.identifier(mapped),
t.identifier(key),
true,
),
),
),
),
Expand Down Expand Up @@ -663,6 +705,7 @@ export function cjsPlugin(
state.set(HAS_ES_MODULE, true);
} else if (left.isMemberExpression()) {
if (isModuleExports(t, left.node)) {
// Should always try to create synthetic default export in this case.
exported.add("default");

if (t.isObjectExpression(expr.node.right)) {
Expand Down
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