packages/babel-plugin-transform-modules-commonjs/src/index.js
import { declare } from "@babel/helper-plugin-utils";
import {
isModule,
rewriteModuleStatementsAndPrepareHeader,
isSideEffectImport,
buildNamespaceInitStatements,
ensureStatementsHoisted,
wrapInterop,
getModuleName,
} from "@babel/helper-module-transforms";
import simplifyAccess from "@babel/helper-simple-access";
import { template, types as t } from "@babel/core";
import { createDynamicImportTransform } from "babel-plugin-dynamic-import-node/utils";
export default declare((api, options) => {
api.assertVersion(7);
const transformImportCall = createDynamicImportTransform(api);
const {
loose,
// 'true' for non-mjs files to strictly have .default, instead of having
// destructuring-like behavior for their properties.
strictNamespace = false,
// 'true' for mjs files to strictly have .default, instead of having
// destructuring-like behavior for their properties.
mjsStrictNamespace = true,
allowTopLevelThis,
strict,
strictMode,
noInterop,
lazy = false,
// Defaulting to 'true' for now. May change before 7.x major.
allowCommonJSExports = true,
} = options;
if (
typeof lazy !== "boolean" &&
typeof lazy !== "function" &&
(!Array.isArray(lazy) || !lazy.every(item => typeof item === "string"))
) {
throw new Error(`.lazy must be a boolean, array of strings, or a function`);
}
if (typeof strictNamespace !== "boolean") {
throw new Error(`.strictNamespace must be a boolean, or undefined`);
}
if (typeof mjsStrictNamespace !== "boolean") {
throw new Error(`.mjsStrictNamespace must be a boolean, or undefined`);
}
const getAssertion = localName => template.expression.ast`
(function(){
throw new Error(
"The CommonJS '" + "${localName}" + "' variable is not available in ES6 modules." +
"Consider setting setting sourceType:script or sourceType:unambiguous in your " +
"Babel config for this file.");
})()
`;
const moduleExportsVisitor = {
ReferencedIdentifier(path) {
const localName = path.node.name;
if (localName !== "module" && localName !== "exports") return;
const localBinding = path.scope.getBinding(localName);
const rootBinding = this.scope.getBinding(localName);
if (
// redeclared in this scope
rootBinding !== localBinding ||
(path.parentPath.isObjectProperty({ value: path.node }) &&
path.parentPath.parentPath.isObjectPattern()) ||
path.parentPath.isAssignmentExpression({ left: path.node }) ||
path.isAssignmentExpression({ left: path.node })
) {
return;
}
path.replaceWith(getAssertion(localName));
},
AssignmentExpression(path) {
const left = path.get("left");
if (left.isIdentifier()) {
const localName = path.node.name;
if (localName !== "module" && localName !== "exports") return;
const localBinding = path.scope.getBinding(localName);
const rootBinding = this.scope.getBinding(localName);
// redeclared in this scope
if (rootBinding !== localBinding) return;
const right = path.get("right");
right.replaceWith(
t.sequenceExpression([right.node, getAssertion(localName)]),
);
} else if (left.isPattern()) {
const ids = left.getOuterBindingIdentifiers();
const localName = Object.keys(ids).filter(localName => {
if (localName !== "module" && localName !== "exports") return false;
return (
this.scope.getBinding(localName) ===
path.scope.getBinding(localName)
);
})[0];
if (localName) {
const right = path.get("right");
right.replaceWith(
t.sequenceExpression([right.node, getAssertion(localName)]),
);
}
}
},
};
return {
name: "transform-modules-commonjs",
pre() {
this.file.set("@babel/plugin-transform-modules-*", "commonjs");
},
visitor: {
CallExpression(path) {
if (!this.file.has("@babel/plugin-proposal-dynamic-import")) return;
if (!path.get("callee").isImport()) return;
let { scope } = path;
do {
scope.rename("require");
} while ((scope = scope.parent));
transformImportCall(this, path.get("callee"));
},
Program: {
exit(path, state) {
if (!isModule(path)) return;
// Rename the bindings auto-injected into the scope so there is no
// risk of conflict between the bindings.
path.scope.rename("exports");
path.scope.rename("module");
path.scope.rename("require");
path.scope.rename("__filename");
path.scope.rename("__dirname");
// Rewrite references to 'module' and 'exports' to throw exceptions.
// These objects are specific to CommonJS and are not available in
// real ES6 implementations.
if (!allowCommonJSExports) {
simplifyAccess(path, new Set(["module", "exports"]));
path.traverse(moduleExportsVisitor, {
scope: path.scope,
});
}
let moduleName = getModuleName(this.file.opts, options);
if (moduleName) moduleName = t.stringLiteral(moduleName);
const { meta, headers } = rewriteModuleStatementsAndPrepareHeader(
path,
{
exportName: "exports",
loose,
strict,
strictMode,
allowTopLevelThis,
noInterop,
lazy,
esNamespaceOnly:
typeof state.filename === "string" &&
/\.mjs$/.test(state.filename)
? mjsStrictNamespace
: strictNamespace,
},
);
for (const [source, metadata] of meta.source) {
const loadExpr = t.callExpression(t.identifier("require"), [
t.stringLiteral(source),
]);
let header;
if (isSideEffectImport(metadata)) {
if (metadata.lazy) throw new Error("Assertion failure");
header = t.expressionStatement(loadExpr);
} else {
const init =
wrapInterop(path, loadExpr, metadata.interop) || loadExpr;
if (metadata.lazy) {
header = template.ast`
function ${metadata.name}() {
const data = ${init};
${metadata.name} = function(){ return data; };
return data;
}
`;
} else {
header = template.ast`
var ${metadata.name} = ${init};
`;
}
}
header.loc = metadata.loc;
headers.push(header);
headers.push(
...buildNamespaceInitStatements(meta, metadata, loose),
);
}
ensureStatementsHoisted(headers);
path.unshiftContainer("body", headers);
},
},
},
};
});