packages/babel-helper-module-transforms/src/index.js
import assert from "assert";
import * as t from "@babel/types";
import template from "@babel/template";
import chunk from "lodash/chunk";
import { isModule } from "@babel/helper-module-imports";
import rewriteThis from "./rewrite-this";
import rewriteLiveReferences from "./rewrite-live-references";
import normalizeAndLoadModuleMetadata, {
hasExports,
isSideEffectImport,
} from "./normalize-and-load-metadata";
export { default as getModuleName } from "./get-module-name";
export { hasExports, isSideEffectImport, isModule, rewriteThis };
/**
* Perform all of the generic ES6 module rewriting needed to handle initial
* module processing. This function will rewrite the majority of the given
* program to reference the modules described by the returned metadata,
* and returns a list of statements for use when initializing the module.
*/
export function rewriteModuleStatementsAndPrepareHeader(
path: NodePath,
{
exportName,
strict,
allowTopLevelThis,
strictMode,
loose,
noInterop,
lazy,
esNamespaceOnly,
},
) {
assert(isModule(path), "Cannot process module statements in a script");
path.node.sourceType = "script";
const meta = normalizeAndLoadModuleMetadata(path, exportName, {
noInterop,
loose,
lazy,
esNamespaceOnly,
});
if (!allowTopLevelThis) {
rewriteThis(path);
}
rewriteLiveReferences(path, meta);
if (strictMode !== false) {
const hasStrict = path.node.directives.some(directive => {
return directive.value.value === "use strict";
});
if (!hasStrict) {
path.unshiftContainer(
"directives",
t.directive(t.directiveLiteral("use strict")),
);
}
}
const headers = [];
if (hasExports(meta) && !strict) {
headers.push(buildESModuleHeader(meta, loose /* enumerable */));
}
const nameList = buildExportNameListDeclaration(path, meta);
if (nameList) {
meta.exportNameListName = nameList.name;
headers.push(nameList.statement);
}
// Create all of the statically known named exports.
headers.push(...buildExportInitializationStatements(path, meta, loose));
return { meta, headers };
}
/**
* Flag a set of statements as hoisted above all else so that module init
* statements all run before user code.
*/
export function ensureStatementsHoisted(statements) {
// Force all of the header fields to be at the top of the file.
statements.forEach(header => {
header._blockHoist = 3;
});
}
/**
* Given an expression for a standard import object, like "require('foo')",
* wrap it in a call to the interop helpers based on the type.
*/
export function wrapInterop(
programPath: NodePath,
expr: Node,
type: InteropType,
): Node {
if (type === "none") {
return null;
}
let helper;
if (type === "default") {
helper = "interopRequireDefault";
} else if (type === "namespace") {
helper = "interopRequireWildcard";
} else {
throw new Error(`Unknown interop: ${type}`);
}
return t.callExpression(programPath.hub.addHelper(helper), [expr]);
}
/**
* Create the runtime initialization statements for a given requested source.
* These will initialize all of the runtime import/export logic that
* can't be handled statically by the statements created by
* buildExportInitializationStatements().
*/
export function buildNamespaceInitStatements(
metadata: ModuleMetadata,
sourceMetadata: SourceModuleMetadata,
loose: boolean = false,
) {
const statements = [];
let srcNamespace = t.identifier(sourceMetadata.name);
if (sourceMetadata.lazy) srcNamespace = t.callExpression(srcNamespace, []);
for (const localName of sourceMetadata.importsNamespace) {
if (localName === sourceMetadata.name) continue;
// Create and assign binding to namespace object
statements.push(
template.statement`var NAME = SOURCE;`({
NAME: localName,
SOURCE: t.cloneNode(srcNamespace),
}),
);
}
if (loose) {
statements.push(...buildReexportsFromMeta(metadata, sourceMetadata, loose));
}
for (const exportName of sourceMetadata.reexportNamespace) {
// Assign export to namespace object.
statements.push(
(sourceMetadata.lazy
? template.statement`
Object.defineProperty(EXPORTS, "NAME", {
enumerable: true,
get: function() {
return NAMESPACE;
}
});
`
: template.statement`EXPORTS.NAME = NAMESPACE;`)({
EXPORTS: metadata.exportName,
NAME: exportName,
NAMESPACE: t.cloneNode(srcNamespace),
}),
);
}
if (sourceMetadata.reexportAll) {
const statement = buildNamespaceReexport(
metadata,
t.cloneNode(srcNamespace),
loose,
);
statement.loc = sourceMetadata.reexportAll.loc;
// Iterate props creating getter for each prop.
statements.push(statement);
}
return statements;
}
const getTemplateForReexport = loose => {
return loose
? template.statement`EXPORTS.EXPORT_NAME = NAMESPACE.IMPORT_NAME;`
: template`
Object.defineProperty(EXPORTS, "EXPORT_NAME", {
enumerable: true,
get: function() {
return NAMESPACE.IMPORT_NAME;
},
});
`;
};
const buildReexportsFromMeta = (meta, metadata, loose) => {
const namespace = metadata.lazy
? t.callExpression(t.identifier(metadata.name), [])
: t.identifier(metadata.name);
const templateForCurrentMode = getTemplateForReexport(loose);
return Array.from(metadata.reexports, ([exportName, importName]) =>
templateForCurrentMode({
EXPORTS: meta.exportName,
EXPORT_NAME: exportName,
NAMESPACE: t.cloneNode(namespace),
IMPORT_NAME: importName,
}),
);
};
/**
* Build an "__esModule" header statement setting the property on a given object.
*/
function buildESModuleHeader(
metadata: ModuleMetadata,
enumerable: boolean = false,
) {
return (enumerable
? template.statement`
EXPORTS.__esModule = true;
`
: template.statement`
Object.defineProperty(EXPORTS, "__esModule", {
value: true,
});
`)({ EXPORTS: metadata.exportName });
}
/**
* Create a re-export initialization loop for a specific imported namespace.
*/
function buildNamespaceReexport(metadata, namespace, loose) {
return (loose
? template.statement`
Object.keys(NAMESPACE).forEach(function(key) {
if (key === "default" || key === "__esModule") return;
VERIFY_NAME_LIST;
EXPORTS[key] = NAMESPACE[key];
});
`
: template.statement`
Object.keys(NAMESPACE).forEach(function(key) {
if (key === "default" || key === "__esModule") return;
VERIFY_NAME_LIST;
Object.defineProperty(EXPORTS, key, {
enumerable: true,
get: function() {
return NAMESPACE[key];
},
});
});
`)({
NAMESPACE: namespace,
EXPORTS: metadata.exportName,
VERIFY_NAME_LIST: metadata.exportNameListName
? template`
if (Object.prototype.hasOwnProperty.call(EXPORTS_LIST, key)) return;
`({ EXPORTS_LIST: metadata.exportNameListName })
: null,
});
}
/**
* Build a statement declaring a variable that contains all of the exported
* variable names in an object so they can easily be referenced from an
* export * from statement to check for conflicts.
*/
function buildExportNameListDeclaration(
programPath: NodePath,
metadata: ModuleMetadata,
) {
const exportedVars = Object.create(null);
for (const data of metadata.local.values()) {
for (const name of data.names) {
exportedVars[name] = true;
}
}
let hasReexport = false;
for (const data of metadata.source.values()) {
for (const exportName of data.reexports.keys()) {
exportedVars[exportName] = true;
}
for (const exportName of data.reexportNamespace) {
exportedVars[exportName] = true;
}
hasReexport = hasReexport || data.reexportAll;
}
if (!hasReexport || Object.keys(exportedVars).length === 0) return null;
const name = programPath.scope.generateUidIdentifier("exportNames");
delete exportedVars.default;
return {
name: name.name,
statement: t.variableDeclaration("var", [
t.variableDeclarator(name, t.valueToNode(exportedVars)),
]),
};
}
/**
* Create a set of statements that will initialize all of the statically-known
* export names with their expected values.
*/
function buildExportInitializationStatements(
programPath: NodePath,
metadata: ModuleMetadata,
loose: boolean = false,
) {
const initStatements = [];
const exportNames = [];
for (const [localName, data] of metadata.local) {
if (data.kind === "import") {
// No-open since these are explicitly set with the "reexports" block.
} else if (data.kind === "hoisted") {
initStatements.push(
buildInitStatement(metadata, data.names, t.identifier(localName)),
);
} else {
exportNames.push(...data.names);
}
}
for (const data of metadata.source.values()) {
if (!loose) {
initStatements.push(...buildReexportsFromMeta(metadata, data, loose));
}
for (const exportName of data.reexportNamespace) {
exportNames.push(exportName);
}
}
initStatements.push(
...chunk(exportNames, 100).map(members => {
return buildInitStatement(
metadata,
members,
programPath.scope.buildUndefinedNode(),
);
}),
);
return initStatements;
}
/**
* Given a set of export names, create a set of nested assignments to
* initialize them all to a given expression.
*/
function buildInitStatement(metadata, exportNames, initExpr) {
return t.expressionStatement(
exportNames.reduce(
(acc, exportName) =>
template.expression`EXPORTS.NAME = VALUE`({
EXPORTS: metadata.exportName,
NAME: exportName,
VALUE: acc,
}),
initExpr,
),
);
}