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495import { describe } from "bun:test";
import { itBundled } from "./expectBundled";
// Tests for CommonJS <> ESM interop, specifically the __toESM helper behavior.
//
// The key insight from the code change:
// - `input_module_type` is set based on the AST's exports_kind (whether the importing
// file uses ESM syntax like import/export or CJS syntax like require/module.exports)
// - When a file uses ESM syntax (import/export), isNodeMode = 1
// - When a file uses CJS syntax (require), __toESM is not used at all
//
// This means:
// - Any file using `import` will always get isNodeMode=1, which IGNORES __esModule
// and always wraps the CJS module as the default export
// - This matches Node.js ESM behavior where importing CJS from .mjs always wraps
// the entire exports object as the default
//
// The __esModule marker is only respected in non-bundled scenarios or when using
// actual CommonJS require() syntax.
describe("bundler", () => {
// ============================================================================
// Tests with ESM syntax (import statements)
// These all use isNodeMode=1, which IGNORES __esModule
// ============================================================================
// Test 1: import with __esModule marker - IGNORED
itBundled("cjs/__toESM_import_syntax_with_esModule", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = { value: 'default export' };
exports.named = 'named export';
`,
},
run: {
// With import syntax, isNodeMode=1, so __esModule is IGNORED
// The entire CJS exports object is wrapped as default
stdout: '{"__esModule":true,"default":{"value":"default export"},"named":"named export"}',
},
});
// Test 2: import WITHOUT __esModule marker
itBundled("cjs/__toESM_import_syntax_without_esModule", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.foo = 'foo';
exports.bar = 'bar';
`,
},
run: {
// Same behavior - entire module wrapped as default
stdout: '{"foo":"foo","bar":"bar"}',
},
});
// Test 3: import with module.exports = function
itBundled("cjs/__toESM_import_syntax_function", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(lib.name + ':' + lib());
`,
"/lib.cjs": /* js */ `
module.exports = function myFunc() { return 'result'; };
`,
},
run: {
stdout: "myFunc:result",
},
});
// Test 4: import with module.exports = primitive
itBundled("cjs/__toESM_import_syntax_primitive", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(lib);
`,
"/lib.cjs": /* js */ `
module.exports = 42;
`,
},
run: {
stdout: "42",
},
});
// Test 5: import with named + default
itBundled("cjs/__toESM_import_syntax_named_and_default", {
files: {
"/entry.js": /* js */ `
import lib, { foo } from './lib.cjs';
console.log(JSON.stringify({ default: lib, named: foo }));
`,
"/lib.cjs": /* js */ `
exports.foo = 'foo value';
exports.bar = 'bar value';
`,
},
run: {
stdout: '{"default":{"foo":"foo value","bar":"bar value"},"named":"foo value"}',
},
});
// Test 6: Namespace import (import *)
itBundled("cjs/__toESM_import_syntax_namespace", {
files: {
"/entry.js": /* js */ `
import * as lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.foo = 'foo';
exports.bar = 'bar';
`,
},
run: {
// Namespace import only gets the CJS exports as-is, no default wrapper
stdout: '{"foo":"foo","bar":"bar"}',
},
});
// ============================================================================
// Tests with different targets
// Target doesn't affect isNodeMode - it's based on syntax
// ============================================================================
// Test 7: target=node
itBundled("cjs/__toESM_target_node", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.x = 1;
exports.y = 2;
`,
},
target: "node",
run: {
stdout: '{"x":1,"y":2}',
},
});
// Test 8: target=browser
itBundled("cjs/__toESM_target_browser", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.x = 1;
exports.y = 2;
`,
},
target: "browser",
run: {
stdout: '{"x":1,"y":2}',
},
});
// Test 9: target=bun
itBundled("cjs/__toESM_target_bun", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.x = 1;
exports.y = 2;
`,
},
target: "bun",
run: {
stdout: '{"x":1,"y":2}',
},
});
// ============================================================================
// Tests with different output formats
// Output format doesn't affect isNodeMode either
// ============================================================================
// Test 10: format=esm
itBundled("cjs/__toESM_format_esm", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = 'the default';
exports.other = 'other';
`,
},
format: "esm",
run: {
// __esModule ignored because we're using import syntax
stdout: '{"__esModule":true,"default":"the default","other":"other"}',
},
});
// Test 11: format=cjs with import syntax
itBundled("cjs/__toESM_format_cjs_with_import", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = 'the default';
exports.other = 'other';
`,
},
format: "cjs",
run: {
// Still ignores __esModule because entry uses import syntax
stdout: '{"__esModule":true,"default":"the default","other":"other"}',
},
});
// ============================================================================
// Tests for .mjs files re-exporting from .cjs
// ============================================================================
// Test 12: .mjs re-exporting default from CJS
itBundled("cjs/__toESM_mjs_reexport", {
files: {
"/entry.js": /* js */ `
import lib from './wrapper.mjs';
console.log(JSON.stringify(lib));
`,
"/wrapper.mjs": /* js */ `
export { default } from './lib.cjs';
`,
"/lib.cjs": /* js */ `
exports.foo = 'foo';
exports.bar = 'bar';
`,
},
run: {
stdout: '{"foo":"foo","bar":"bar"}',
},
});
// Test 13: .mjs re-exporting with __esModule (still ignored)
itBundled("cjs/__toESM_mjs_reexport_with_esModule", {
files: {
"/entry.js": /* js */ `
import lib from './wrapper.mjs';
console.log(JSON.stringify(lib));
`,
"/wrapper.mjs": /* js */ `
export { default } from './lib.cjs';
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = { value: 'from cjs' };
exports.other = 'other';
`,
},
run: {
// __esModule ignored - entire module wrapped as default
stdout: '{"__esModule":true,"default":{"value":"from cjs"},"other":"other"}',
},
});
// Test 14: Deep re-export chain
itBundled("cjs/__toESM_deep_reexport_chain", {
files: {
"/entry.js": /* js */ `
import lib from './layer1.mjs';
console.log(JSON.stringify(lib));
`,
"/layer1.mjs": /* js */ `
export { default } from './layer2.mjs';
`,
"/layer2.mjs": /* js */ `
export { default } from './lib.cjs';
`,
"/lib.cjs": /* js */ `
exports.deep = 'value';
`,
},
run: {
stdout: '{"deep":"value"}',
},
});
// Test 15: Re-export with rename
itBundled("cjs/__toESM_reexport_with_rename", {
files: {
"/entry.js": /* js */ `
import { myDefault } from './wrapper.mjs';
console.log(JSON.stringify(myDefault));
`,
"/wrapper.mjs": /* js */ `
export { default as myDefault } from './lib.cjs';
`,
"/lib.cjs": /* js */ `
exports.x = 1;
`,
},
run: {
stdout: '{"x":1}',
},
});
// ============================================================================
// Edge cases
// ============================================================================
// Test 16: CJS with a property named "default" but no __esModule
itBundled("cjs/__toESM_default_prop_no_esModule", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.default = 'I am a prop named default';
exports.other = 'other';
`,
},
run: {
// Entire module wrapped, including the .default property
stdout: '{"default":"I am a prop named default","other":"other"}',
},
});
// Test 17: Mixed import styles
itBundled("cjs/__toESM_mixed_import_styles", {
files: {
"/entry.js": /* js */ `
import defaultExport from './lib.cjs';
import { foo } from './lib.cjs';
import * as namespace from './lib.cjs';
console.log(JSON.stringify({
default: defaultExport,
named: foo,
namespace: namespace
}));
`,
"/lib.cjs": /* js */ `
exports.foo = 'foo';
exports.bar = 'bar';
`,
},
run: {
stdout:
'{"default":{"foo":"foo","bar":"bar"},"named":"foo","namespace":{"default":{"foo":"foo","bar":"bar"},"foo":"foo","bar":"bar"}}',
},
});
// Test 18: __esModule with non-true value
itBundled("cjs/__toESM_esModule_non_true", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = 'truthy';
exports.default = { value: 'default' };
exports.other = 'other';
`,
},
run: {
// Even if __esModule were respected, only `true` would work
// But it's ignored anyway due to import syntax
stdout: '{"__esModule":"truthy","default":{"value":"default"},"other":"other"}',
},
});
// Test 19: __esModule = false
itBundled("cjs/__toESM_esModule_false", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = false;
exports.default = { value: 'ignored' };
exports.foo = 'foo';
`,
},
run: {
// Entire module wrapped as default (since we use import syntax)
stdout: '{"__esModule":false,"default":{"value":"ignored"},"foo":"foo"}',
},
});
// Test 20: module.exports with __esModule
itBundled("cjs/__toESM_module_exports_with_esModule", {
files: {
"/entry.js": /* js */ `
import lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
module.exports = {
__esModule: true,
default: { value: 'nested' },
other: 'prop'
};
`,
},
run: {
// __esModule is in the object but ignored due to import syntax
stdout: '{"__esModule":true,"default":{"value":"nested"},"other":"prop"}',
},
});
// Test 21: Input=ESM, output=CJS, importing CJS with __esModule and named imports
// This test covers the specific fix for printing __toESM when output format is CJS
// and input uses ESM syntax to import both default and named exports from CJS with __esModule
itBundled("cjs/__toESM_input_esm_output_cjs_wrapper_print", {
files: {
"/entry.js": /* js */ `
import lib, { named } from "./lib.cjs";
console.log(JSON.stringify({ default: lib, named }));
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = { value: "default" };
exports.named = "named export";
`,
},
format: "cjs",
run: {
// With the fix: ignores __esModule, wraps entire module as default
// So default gets the whole exports object, named gets the named property
stdout:
'{"default":{"__esModule":true,"default":{"value":"default"},"named":"named export"},"named":"named export"}',
},
});
// Test 22: Star import with __esModule
itBundled("cjs/__toESM_star_import_with_esModule", {
files: {
"/entry.js": /* js */ `
import * as lib from './lib.cjs';
console.log(JSON.stringify(lib));
`,
"/lib.cjs": /* js */ `
exports.__esModule = true;
exports.default = 'default';
exports.named = 'named';
`,
},
run: {
// Star import gets the exports as-is, no wrapper
stdout: '{"named":"named","default":"default","__esModule":true}',
},
});
// Test 23: Practical example - importing lodash-like library
itBundled("cjs/__toESM_practical_lodash_style", {
files: {
"/entry.js": /* js */ `
import _ from './lodash.cjs';
import { map } from './lodash.cjs';
console.log(JSON.stringify({
hasMap: typeof _.map === 'function',
same: _.map === map
}));
`,
"/lodash.cjs": /* js */ `
exports.map = function(arr, fn) { return arr.map(fn); };
exports.filter = function(arr, fn) { return arr.filter(fn); };
`,
},
run: {
// Default gets entire module, named import gets specific function
// Both reference the same function
stdout: '{"hasMap":true,"same":true}',
},
});
});