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rewrite-live-references.ts
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rewrite-live-references.ts
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import assert from "assert";
import {
assignmentExpression,
callExpression,
cloneNode,
expressionStatement,
getOuterBindingIdentifiers,
identifier,
isMemberExpression,
isVariableDeclaration,
jsxIdentifier,
jsxMemberExpression,
memberExpression,
numericLiteral,
sequenceExpression,
stringLiteral,
variableDeclaration,
variableDeclarator,
} from "@babel/types";
import type * as t from "@babel/types";
import template from "@babel/template";
import type { NodePath, Visitor, Scope } from "@babel/traverse";
import simplifyAccess from "@babel/helper-simple-access";
import type { ModuleMetadata } from "./normalize-and-load-metadata";
interface RewriteReferencesVisitorState {
exported: Map<any, any>;
metadata: ModuleMetadata;
requeueInParent: (path: NodePath) => void;
scope: Scope;
imported: Map<any, any>;
buildImportReference: (
[source, importName, localName]: readonly [string, string, string],
identNode: t.Identifier | t.CallExpression | t.JSXIdentifier,
) => any;
seen: WeakSet<object>;
}
interface RewriteBindingInitVisitorState {
exported: Map<any, any>;
metadata: ModuleMetadata;
requeueInParent: (path: NodePath) => void;
scope: Scope;
}
function isInType(path: NodePath) {
do {
switch (path.parent.type) {
case "TSTypeAnnotation":
case "TSTypeAliasDeclaration":
case "TSTypeReference":
case "TypeAnnotation":
case "TypeAlias":
return true;
case "ExportSpecifier":
return (
(
path.parentPath.parent as
| t.ExportDefaultDeclaration
| t.ExportNamedDeclaration
).exportKind === "type"
);
default:
if (path.parentPath.isStatement() || path.parentPath.isExpression()) {
return false;
}
}
} while ((path = path.parentPath));
}
export default function rewriteLiveReferences(
programPath: NodePath<t.Program>,
metadata: ModuleMetadata,
) {
const imported = new Map();
const exported = new Map();
const requeueInParent = (path: NodePath) => {
// Manually re-queue `exports.default =` expressions so that the ES3
// transform has an opportunity to convert them. Ideally this would
// happen automatically from the replaceWith above. See #4140 for
// more info.
programPath.requeue(path);
};
for (const [source, data] of metadata.source) {
for (const [localName, importName] of data.imports) {
imported.set(localName, [source, importName, null]);
}
for (const localName of data.importsNamespace) {
imported.set(localName, [source, null, localName]);
}
}
for (const [local, data] of metadata.local) {
let exportMeta = exported.get(local);
if (!exportMeta) {
exportMeta = [];
exported.set(local, exportMeta);
}
exportMeta.push(...data.names);
}
// Rewrite initialization of bindings to update exports.
const rewriteBindingInitVisitorState: RewriteBindingInitVisitorState = {
metadata,
requeueInParent,
scope: programPath.scope,
exported, // local name => exported name list
};
programPath.traverse(
rewriteBindingInitVisitor,
rewriteBindingInitVisitorState,
);
simplifyAccess(
programPath,
// NOTE(logan): The 'Array.from' calls are to make this code with in loose mode.
new Set([...Array.from(imported.keys()), ...Array.from(exported.keys())]),
false,
);
// Rewrite reads/writes from imports and exports to have the correct behavior.
const rewriteReferencesVisitorState: RewriteReferencesVisitorState = {
seen: new WeakSet(),
metadata,
requeueInParent,
scope: programPath.scope,
imported, // local / import
exported, // local name => exported name list
buildImportReference: ([source, importName, localName], identNode) => {
const meta = metadata.source.get(source);
if (localName) {
if (meta.lazy) {
identNode = callExpression(
// @ts-expect-error Fixme: we should handle the case when identNode is a JSXIdentifier
identNode,
[],
);
}
return identNode;
}
let namespace: t.Expression = identifier(meta.name);
if (meta.lazy) namespace = callExpression(namespace, []);
if (importName === "default" && meta.interop === "node-default") {
return namespace;
}
const computed = metadata.stringSpecifiers.has(importName);
return memberExpression(
namespace,
computed ? stringLiteral(importName) : identifier(importName),
computed,
);
},
};
programPath.traverse(rewriteReferencesVisitor, rewriteReferencesVisitorState);
}
/**
* A visitor to inject export update statements during binding initialization.
*/
const rewriteBindingInitVisitor: Visitor<RewriteBindingInitVisitorState> = {
Scope(path) {
path.skip();
},
ClassDeclaration(path) {
const { requeueInParent, exported, metadata } = this;
const { id } = path.node;
if (!id) throw new Error("Expected class to have a name");
const localName = id.name;
const exportNames = exported.get(localName) || [];
if (exportNames.length > 0) {
const statement = expressionStatement(
buildBindingExportAssignmentExpression(
metadata,
exportNames,
identifier(localName),
path.scope,
),
);
// @ts-expect-error todo(flow->ts): avoid mutations
statement._blockHoist = path.node._blockHoist;
requeueInParent(path.insertAfter(statement)[0]);
}
},
VariableDeclaration(path) {
const { requeueInParent, exported, metadata } = this;
Object.keys(path.getOuterBindingIdentifiers()).forEach(localName => {
const exportNames = exported.get(localName) || [];
if (exportNames.length > 0) {
const statement = expressionStatement(
buildBindingExportAssignmentExpression(
metadata,
exportNames,
identifier(localName),
path.scope,
),
);
// @ts-expect-error todo(flow->ts): avoid mutations
statement._blockHoist = path.node._blockHoist;
requeueInParent(path.insertAfter(statement)[0]);
}
});
},
};
const buildBindingExportAssignmentExpression = (
metadata: ModuleMetadata,
exportNames: string[],
localExpr: t.Expression,
scope: Scope,
) => {
const exportsObjectName = metadata.exportName;
for (
let currentScope = scope;
currentScope != null;
currentScope = currentScope.parent
) {
if (currentScope.hasOwnBinding(exportsObjectName)) {
currentScope.rename(exportsObjectName);
}
}
return (exportNames || []).reduce((expr, exportName) => {
// class Foo {} export { Foo, Foo as Bar };
// as
// class Foo {} exports.Foo = exports.Bar = Foo;
const { stringSpecifiers } = metadata;
const computed = stringSpecifiers.has(exportName);
return assignmentExpression(
"=",
memberExpression(
identifier(exportsObjectName),
computed ? stringLiteral(exportName) : identifier(exportName),
/* computed */ computed,
),
expr,
);
}, localExpr);
};
const buildImportThrow = (localName: string) => {
return template.expression.ast`
(function() {
throw new Error('"' + '${localName}' + '" is read-only.');
})()
`;
};
const rewriteReferencesVisitor: Visitor<RewriteReferencesVisitorState> = {
ReferencedIdentifier(path) {
const { seen, buildImportReference, scope, imported, requeueInParent } =
this;
if (seen.has(path.node)) return;
seen.add(path.node);
const localName = path.node.name;
const importData = imported.get(localName);
if (importData) {
if (isInType(path)) {
throw path.buildCodeFrameError(
`Cannot transform the imported binding "${localName}" since it's also used in a type annotation. ` +
`Please strip type annotations using @babel/preset-typescript or @babel/preset-flow.`,
);
}
const localBinding = path.scope.getBinding(localName);
const rootBinding = scope.getBinding(localName);
// redeclared in this scope
if (rootBinding !== localBinding) return;
const ref = buildImportReference(importData, path.node);
// Preserve the binding location so that sourcemaps are nicer.
ref.loc = path.node.loc;
if (
(path.parentPath.isCallExpression({ callee: path.node }) ||
path.parentPath.isOptionalCallExpression({ callee: path.node }) ||
path.parentPath.isTaggedTemplateExpression({ tag: path.node })) &&
isMemberExpression(ref)
) {
path.replaceWith(sequenceExpression([numericLiteral(0), ref]));
} else if (path.isJSXIdentifier() && isMemberExpression(ref)) {
const { object, property } = ref;
path.replaceWith(
jsxMemberExpression(
// @ts-expect-error todo(flow->ts): possible bug `object` might not have a name
jsxIdentifier(object.name),
// @ts-expect-error todo(flow->ts): possible bug `property` might not have a name
jsxIdentifier(property.name),
),
);
} else {
path.replaceWith(ref);
}
requeueInParent(path);
// The path could have been replaced with an identifier that would
// otherwise be re-visited, so we skip processing its children.
path.skip();
}
},
UpdateExpression(path) {
const {
scope,
seen,
imported,
exported,
requeueInParent,
buildImportReference,
} = this;
if (seen.has(path.node)) return;
seen.add(path.node);
const arg = path.get("argument");
// No change needed
if (arg.isMemberExpression()) return;
const update = path.node;
if (arg.isIdentifier()) {
const localName = arg.node.name;
// redeclared in this scope
if (scope.getBinding(localName) !== path.scope.getBinding(localName)) {
return;
}
const exportedNames = exported.get(localName);
const importData = imported.get(localName);
if (exportedNames?.length > 0 || importData) {
if (importData) {
path.replaceWith(
assignmentExpression(
update.operator[0] + "=",
buildImportReference(importData, arg.node),
buildImportThrow(localName),
),
);
} else if (update.prefix) {
// ++foo
// => exports.foo = ++foo
path.replaceWith(
buildBindingExportAssignmentExpression(
this.metadata,
exportedNames,
cloneNode(update),
path.scope,
),
);
} else {
// foo++
// => (ref = i++, exports.i = i, ref)
const ref = scope.generateDeclaredUidIdentifier(localName);
path.replaceWith(
sequenceExpression([
assignmentExpression("=", cloneNode(ref), cloneNode(update)),
buildBindingExportAssignmentExpression(
this.metadata,
exportedNames,
identifier(localName),
path.scope,
),
cloneNode(ref),
]),
);
}
}
}
requeueInParent(path);
path.skip();
},
AssignmentExpression: {
exit(path) {
const {
scope,
seen,
imported,
exported,
requeueInParent,
buildImportReference,
} = this;
if (seen.has(path.node)) return;
seen.add(path.node);
const left = path.get("left");
// No change needed
if (left.isMemberExpression()) return;
if (left.isIdentifier()) {
// Simple update-assign foo += 1; export { foo };
// => exports.foo = (foo += 1);
const localName = left.node.name;
// redeclared in this scope
if (scope.getBinding(localName) !== path.scope.getBinding(localName)) {
return;
}
const exportedNames = exported.get(localName);
const importData = imported.get(localName);
if (exportedNames?.length > 0 || importData) {
assert(path.node.operator === "=", "Path was not simplified");
const assignment = path.node;
if (importData) {
assignment.left = buildImportReference(importData, left.node);
assignment.right = sequenceExpression([
assignment.right,
buildImportThrow(localName),
]);
}
path.replaceWith(
buildBindingExportAssignmentExpression(
this.metadata,
exportedNames,
assignment,
path.scope,
),
);
requeueInParent(path);
}
} else {
const ids = left.getOuterBindingIdentifiers();
const programScopeIds = Object.keys(ids).filter(
localName =>
scope.getBinding(localName) === path.scope.getBinding(localName),
);
const id = programScopeIds.find(localName => imported.has(localName));
if (id) {
path.node.right = sequenceExpression([
path.node.right,
buildImportThrow(id),
]);
}
// Complex ({a, b, c} = {}); export { a, c };
// => ({a, b, c} = {}), (exports.a = a, exports.c = c);
const items: t.Expression[] = [];
programScopeIds.forEach(localName => {
const exportedNames = exported.get(localName) || [];
if (exportedNames.length > 0) {
items.push(
buildBindingExportAssignmentExpression(
this.metadata,
exportedNames,
identifier(localName),
path.scope,
),
);
}
});
if (items.length > 0) {
let node: t.Node = sequenceExpression(items);
if (path.parentPath.isExpressionStatement()) {
node = expressionStatement(node);
// @ts-expect-error todo(flow->ts): avoid mutations
node._blockHoist = path.parentPath.node._blockHoist;
}
const statement = path.insertAfter(node)[0];
requeueInParent(statement);
}
}
},
},
"ForOfStatement|ForInStatement"(
path: NodePath<t.ForOfStatement | t.ForInStatement>,
) {
const { scope, node } = path;
const { left } = node;
const { exported, imported, scope: programScope } = this;
if (!isVariableDeclaration(left)) {
let didTransformExport = false,
importConstViolationName;
const loopBodyScope = path.get("body").scope;
for (const name of Object.keys(getOuterBindingIdentifiers(left))) {
if (programScope.getBinding(name) === scope.getBinding(name)) {
if (exported.has(name)) {
didTransformExport = true;
if (loopBodyScope.hasOwnBinding(name)) {
loopBodyScope.rename(name);
}
}
if (imported.has(name) && !importConstViolationName) {
importConstViolationName = name;
}
}
}
if (!didTransformExport && !importConstViolationName) {
return;
}
path.ensureBlock();
const bodyPath = path.get("body");
const newLoopId = scope.generateUidIdentifierBasedOnNode(left);
path
.get("left")
.replaceWith(
variableDeclaration("let", [
variableDeclarator(cloneNode(newLoopId)),
]),
);
scope.registerDeclaration(path.get("left"));
if (didTransformExport) {
bodyPath.unshiftContainer(
"body",
expressionStatement(assignmentExpression("=", left, newLoopId)),
);
}
if (importConstViolationName) {
bodyPath.unshiftContainer(
"body",
expressionStatement(buildImportThrow(importConstViolationName)),
);
}
}
},
};