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import { types as t } from '@babel/core';
import invariant from 'ts-invariant';
type Scope = Map<string, Set<t.Identifier | t.MemberExpression>>;
export type ScopeId = number | 'global' | 'exports';
export type DeclareHandler = (
identifier: t.Identifier,
from: t.Identifier | null
) => void;
const ResolvedNode = Symbol('ResolvedNode');
const functionScopes = new WeakSet<Scope>();
export class PromisedNode<T = t.Node> {
static is<TNode>(obj: any): obj is PromisedNode<TNode> {
return obj && ResolvedNode in obj;
}
[ResolvedNode]: T | undefined;
get identifier(): T | undefined {
return this[ResolvedNode];
}
}
export const resolveNode = <T = t.Node>(
obj: T | PromisedNode<T> | undefined
): T | undefined => (PromisedNode.is<T>(obj) ? obj.identifier : obj);
const getExportName = (node: t.Node): string => {
invariant(
t.isMemberExpression(node),
`getExportName expects MemberExpression but received ${node.type}`
);
const { object, property } = node;
invariant(
t.isIdentifier(object) && object.name === 'exports',
`getExportName expects a member expression with 'exports'`
);
invariant(
t.isIdentifier(property) || t.isStringLiteral(property),
`getExportName supports only identifiers and literals as names of exported values`
);
const name = t.isIdentifier(property) ? property.name : property.value;
return `exports.${name}`;
};
const scopeIds = new WeakMap<Scope, ScopeId>();
const getId = (scope: Scope, identifier: t.Identifier | string): string => {
const scopeId = scopeIds.get(scope);
return `${scopeId}:${
typeof identifier === 'string' ? identifier : identifier.name
}`;
};
export default class ScopeManager {
public static globalExportsIdentifier = t.identifier('exports');
public static globalModuleIdentifier = t.identifier('module');
private nextId = 0;
private readonly stack: Array<Scope> = [];
private readonly map: Map<ScopeId, Scope> = new Map();
private readonly handlers: Map<ScopeId, Array<DeclareHandler>> = new Map();
private readonly declarations: Map<
string,
t.Identifier | t.MemberExpression | PromisedNode<t.Identifier>
> = new Map();
private get global(): Scope {
return this.map.get('global')!;
}
constructor() {
this.new(true, 'global');
this.declare(ScopeManager.globalExportsIdentifier, false);
this.declare(ScopeManager.globalModuleIdentifier, false);
}
new(isFunction: boolean, scopeId: ScopeId = this.nextId++): Scope {
const scope: Scope = new Map();
if (isFunction) {
functionScopes.add(scope);
}
scopeIds.set(scope, scopeId);
this.map.set(scopeId, scope);
this.handlers.set(scopeId, []);
this.stack.unshift(scope);
return scope;
}
dispose(): Scope | undefined {
const disposed = this.stack.shift();
if (disposed) {
this.map.delete(scopeIds.get(disposed)!);
}
return disposed;
}
declare(
identifierOrMemberExpression: t.Identifier | t.MemberExpression,
isHoistable: boolean,
from: t.Identifier | null = null,
stack = 0
): void {
if (t.isMemberExpression(identifierOrMemberExpression)) {
// declare receives MemberExpression only if it's `exports.something` expression
const memberExp = identifierOrMemberExpression;
const name = getExportName(memberExp);
if (!this.global.has(name)) {
this.global.set(name, new Set());
}
// There can be a few `export.foo = …` statements, but we need only the last one
this.declarations.set(getId(this.global, name), memberExp);
this.global.get(name)!.add(memberExp);
return;
}
const identifier = identifierOrMemberExpression;
const idName = identifier.name;
const scope = this.stack
.slice(stack)
.find((s) => !isHoistable || functionScopes.has(s))!;
if (this.global.has(idName)) {
// It's probably a declaration of a previous referenced identifier
// Let's use naïve implementation of hoisting
const promise = this.declarations.get(
getId(this.global, identifier)
)! as PromisedNode<t.Identifier>;
promise[ResolvedNode] = identifier;
scope.set(
idName,
new Set([identifier, ...Array.from(this.global.get(idName)!)])
);
this.global.delete(idName);
} else {
scope.set(idName, new Set([identifier]));
}
this.declarations.set(getId(scope, identifier), identifier);
const handlers = this.handlers.get(scopeIds.get(scope)!)!;
handlers.forEach((handler) => handler(identifier, from));
}
addReference(
identifierOrMemberExpression: t.Identifier | t.MemberExpression
): t.Identifier | t.MemberExpression | PromisedNode {
const name = t.isIdentifier(identifierOrMemberExpression)
? identifierOrMemberExpression.name
: getExportName(identifierOrMemberExpression);
const scope = this.stack.find((s) => s.has(name)) ?? this.global;
const id = getId(scope, name);
if (scope === this.global && !scope.has(name)) {
scope.set(name, new Set());
this.declarations.set(id, new PromisedNode());
}
scope.get(name)!.add(identifierOrMemberExpression);
return this.declarations.get(id)!;
}
whereIsDeclared(identifier: t.Identifier): ScopeId | undefined {
const name = identifier.name;
const scope = this.stack.find(
(s) => s.has(name) && s.get(name)!.has(identifier)
);
if (scope) {
return scopeIds.get(scope);
}
if (this.global.has(name)) {
return 'global';
}
return undefined;
}
getDeclaration(
identifierOrMemberExpOrName: t.Identifier | t.MemberExpression | string
): t.Identifier | t.MemberExpression | undefined {
let name: string;
if (typeof identifierOrMemberExpOrName === 'string') {
name = identifierOrMemberExpOrName;
} else if (t.isMemberExpression(identifierOrMemberExpOrName)) {
name = getId(this.global, getExportName(identifierOrMemberExpOrName));
} else {
const scopeId = this.whereIsDeclared(identifierOrMemberExpOrName);
if (scopeId === undefined) {
return undefined;
}
name = getId(this.map.get(scopeId)!, identifierOrMemberExpOrName);
}
return resolveNode(this.declarations.get(name));
}
addDeclareHandler(handler: DeclareHandler): () => void {
const scopeId = scopeIds.get(this.stack[0])!;
this.handlers.get(scopeId)!.push(handler);
return () => {
const handlers = this.handlers.get(scopeId)!.filter((h) => h !== handler);
this.handlers.set(scopeId, handlers);
};
}
}
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