index.js

/* eslint max-len: 0 */

import includes from "lodash/includes";
import repeat from "lodash/repeat";
import Renamer from "./lib/renamer";
import type NodePath from "../path";
import traverse from "../index";
import defaults from "lodash/defaults";
import * as messages from "babel-messages";
import Binding from "./binding";
import globals from "globals";
import * as t from "babel-types";
import { scope as scopeCache } from "../cache";

// Number of calls to the crawl method to figure out whether we're
// somewhere inside a call that was trigerred by call. This is meant
// to be used to figure out whether a warning should be trigerred.
// See `warnOnFlowBinding`.
let _crawlCallsCount = 0;

/**
 * To avoid creating a new Scope instance for each traversal, we maintain a cache on the
 * node itself containing all scopes it has been associated with.
 */

function getCache(path, parentScope, self) {
  let scopes: Array<Scope> = scopeCache.get(path.node) || [];

  for (let scope of scopes) {
    if (scope.parent === parentScope && scope.path === path) return scope;
  }

  scopes.push(self);

  if (!scopeCache.has(path.node)) {
    scopeCache.set(path.node, scopes);
  }
}

// Recursively gathers the identifying names of a node.
function gatherNodeParts(node: Object, parts: Array) {
  if (t.isModuleDeclaration(node)) {
    if (node.source) {
      gatherNodeParts(node.source, parts);
    } else if (node.specifiers && node.specifiers.length) {
      for (let specifier of (node.specifiers: Array)) {
        gatherNodeParts(specifier, parts);
      }
    } else if (node.declaration) {
      gatherNodeParts(node.declaration, parts);
    }
  } else if (t.isModuleSpecifier(node)) {
    gatherNodeParts(node.local, parts);
  } else if (t.isMemberExpression(node)) {
    gatherNodeParts(node.object, parts);
    gatherNodeParts(node.property, parts);
  } else if (t.isIdentifier(node)) {
    parts.push(node.name);
  } else if (t.isLiteral(node)) {
    parts.push(node.value);
  } else if (t.isCallExpression(node)) {
    gatherNodeParts(node.callee, parts);
  } else if (t.isObjectExpression(node) || t.isObjectPattern(node)) {
    for (let prop of (node.properties: Array)) {
      gatherNodeParts(prop.key || prop.argument, parts);
    }
  }
}

//

let collectorVisitor = {
  For(path) {
    for (let key of (t.FOR_INIT_KEYS: Array)) {
      let declar = path.get(key);
      if (declar.isVar()) path.scope.getFunctionParent().registerBinding("var", declar);
    }
  },

  Declaration(path) {
    // delegate block scope handling to the `blockVariableVisitor`
    if (path.isBlockScoped()) return;

    // this will be hit again once we traverse into it after this iteration
    if (path.isExportDeclaration() && path.get("declaration").isDeclaration()) return;

    // TODO(amasad): remove support for flow as bindings (See warning below).
    //if (path.isFlow()) return;

    // we've ran into a declaration!
    path.scope.getFunctionParent().registerDeclaration(path);
  },

  ReferencedIdentifier(path, state) {
    state.references.push(path);
  },

  ForXStatement(path, state) {
    let left = path.get("left");
    if (left.isPattern() || left.isIdentifier()) {
      state.constantViolations.push(left);
    }
  },

  ExportDeclaration: {
    exit(path) {
      const { node, scope } = path;
      let declar = node.declaration;
      if (t.isClassDeclaration(declar) || t.isFunctionDeclaration(declar)) {
        let id = declar.id;
        if (!id) return;

        let binding = scope.getBinding(id.name);
        if (binding) binding.reference(path);
      } else if (t.isVariableDeclaration(declar)) {
        for (let decl of (declar.declarations: Array<Object>)) {
          let ids = t.getBindingIdentifiers(decl);
          for (let name in ids) {
            let binding = scope.getBinding(name);
            if (binding) binding.reference(path);
          }
        }
      }
    }
  },

  LabeledStatement(path) {
    path.scope.getProgramParent().addGlobal(path.node);
    path.scope.getBlockParent().registerDeclaration(path);
  },

  AssignmentExpression(path, state) {
    state.assignments.push(path);
  },

  UpdateExpression(path, state) {
    state.constantViolations.push(path.get("argument"));
  },

  UnaryExpression(path, state) {
    if (path.node.operator === "delete") {
      state.constantViolations.push(path.get("argument"));
    }
  },

  BlockScoped(path) {
    let scope = path.scope;
    if (scope.path === path) scope = scope.parent;
    scope.getBlockParent().registerDeclaration(path);
  },

  ClassDeclaration(path) {
    let id = path.node.id;
    if (!id) return;

    let name = id.name;
    path.scope.bindings[name] = path.scope.getBinding(name);
  },

  Block(path) {
    let paths = path.get("body");
    for (let bodyPath of (paths: Array)) {
      if (bodyPath.isFunctionDeclaration()) {
        path.scope.getBlockParent().registerDeclaration(bodyPath);
      }
    }
  }
};

let uid = 0;

export default class Scope {

  /**
   * This searches the current "scope" and collects all references/bindings
   * within.
   */

  constructor(path: NodePath, parentScope?: Scope) {
    if (parentScope && parentScope.block === path.node) {
      return parentScope;
    }

    let cached = getCache(path, parentScope, this);
    if (cached) return cached;

    this.uid = uid++;
    this.parent = parentScope;
    this.hub    = path.hub;

    this.parentBlock = path.parent;
    this.block       = path.node;
    this.path        = path;

    this.labels      = new Map();
  }

  /**
   * Globals.
   */

  static globals = Object.keys(globals.builtin);

  /**
   * Variables available in current context.
   */

  static contextVariables = [
    "arguments",
    "undefined",
    "Infinity",
    "NaN"
  ];

  /**
   * Traverse node with current scope and path.
   */

  traverse(node: Object, opts: Object, state?) {
    traverse(node, opts, this, state, this.path);
  }

  /**
   * Generate a unique identifier and add it to the current scope.
   */

  generateDeclaredUidIdentifier(name: string = "temp") {
    let id = this.generateUidIdentifier(name);
    this.push({ id });
    return id;
  }

  /**
   * Generate a unique identifier.
   */

  generateUidIdentifier(name: string = "temp") {
    return t.identifier(this.generateUid(name));
  }

  /**
   * Generate a unique `_id1` binding.
   */

  generateUid(name: string = "temp") {
    name = t.toIdentifier(name).replace(/^_+/, "").replace(/[0-9]+$/g, "");

    let uid;
    let i = 0;
    do {
      uid = this._generateUid(name, i);
      i++;
    } while (this.hasLabel(uid) || this.hasBinding(uid) || this.hasGlobal(uid) || this.hasReference(uid));

    let program = this.getProgramParent();
    program.references[uid] = true;
    program.uids[uid] = true;

    return uid;
  }

  /**
   * Generate an `_id1`.
   */

  _generateUid(name, i) {
    let id = name;
    if (i > 1) id += i;
    return `_${id}`;
  }

  /**
   * Generate a unique identifier based on a node.
   */

  generateUidIdentifierBasedOnNode(parent: Object, defaultName?: String):  Object {
    let node = parent;

    if (t.isAssignmentExpression(parent)) {
      node = parent.left;
    } else if (t.isVariableDeclarator(parent)) {
      node = parent.id;
    } else if (t.isObjectProperty(node) || t.isObjectMethod(node)) {
      node = node.key;
    }

    const parts = [];
    gatherNodeParts(node, parts);

    let id = parts.join("$");
    id = id.replace(/^_/, "") || defaultName || "ref";

    return this.generateUidIdentifier(id.slice(0, 20));
  }

  /**
   * Determine whether evaluating the specific input `node` is a consequenceless reference. ie.
   * evaluating it wont result in potentially arbitrary code from being ran. The following are
   * whitelisted and determined not to cause side effects:
   *
   *  - `this` expressions
   *  - `super` expressions
   *  - Bound identifiers
   */

  isStatic(node: Object): boolean {
    if (t.isThisExpression(node) || t.isSuper(node)) {
      return true;
    }

    if (t.isIdentifier(node)) {
      let binding = this.getBinding(node.name);
      if (binding) {
        return binding.constant;
      } else {
        return this.hasBinding(node.name);
      }
    }

    return false;
  }

  /**
   * Possibly generate a memoised identifier if it is not static and has consequences.
   */

  maybeGenerateMemoised(node: Object, dontPush?: boolean): ?Object {
    if (this.isStatic(node)) {
      return null;
    } else {
      let id = this.generateUidIdentifierBasedOnNode(node);
      if (!dontPush) this.push({ id });
      return id;
    }
  }

  checkBlockScopedCollisions(local, kind: string, name: string, id: Object) {
    // ignore parameters
    if (kind === "param") return;

    // ignore hoisted functions if there's also a local let
    if (kind === "hoisted" && local.kind === "let") return;

    let duplicate = false;

    // don't allow duplicate bindings to exist alongside
    if (!duplicate) duplicate = kind === "let" || local.kind === "let" || local.kind === "const" || local.kind === "module";

    // don't allow a local of param with a kind of let
    if (!duplicate) duplicate = local.kind === "param" && (kind === "let" || kind === "const");

    if (duplicate) {
      const errorMsg = messages.get("scopeDuplicateDeclaration", name);
      throw this.hub.buildError ? this.hub.buildError(id, errorMsg, TypeError) : new TypeError(errorMsg);
    }
  }

  rename(oldName: string, newName: string, block?) {
    let binding = this.getBinding(oldName);
    if (binding) {
      newName = newName || this.generateUidIdentifier(oldName).name;
      return new Renamer(binding, oldName, newName).rename(block);
    }
  }

  _renameFromMap(map, oldName, newName, value) {
    if (map[oldName]) {
      map[newName] = value;
      map[oldName] = null;
    }
  }

  dump() {
    let sep = repeat("-", 60);
    console.log(sep);
    let scope = this;
    do {
      console.log("#", scope.block.type);
      for (let name in scope.bindings) {
        let binding = scope.bindings[name];
        console.log(" -", name, {
          constant: binding.constant,
          references: binding.references,
          violations: binding.constantViolations.length,
          kind: binding.kind
        });
      }
    } while (scope = scope.parent);
    console.log(sep);
  }

  toArray(node: Object, i?: number) {

    if (t.isIdentifier(node)) {
      let binding = this.getBinding(node.name);
      if (binding && binding.constant && binding.path.isGenericType("Array")) return node;
    }

    if (t.isArrayExpression(node)) {
      return node;
    }

    if (t.isIdentifier(node, { name: "arguments" })) {
      return t.callExpression(
        t.memberExpression(
          t.memberExpression(
            t.memberExpression(
              t.identifier("Array"),
              t.identifier("prototype")
            ),
            t.identifier("slice")
          ),
          t.identifier("call")
        ),
        [node]
      );
    }

    let helperName = "toArray";
    let args = [node];
    if (i === true) {
      helperName = "toConsumableArray";
    } else if (i) {
      args.push(t.numericLiteral(i));
      helperName = "slicedToArray";
      // TODO if (this.hub.isLoose("es6.forOf")) helperName += "-loose";
    }
    return t.callExpression(this.hub.addHelper(helperName), args);
  }

  hasLabel(name: string) {
    return !!this.getLabel(name);
  }

  getLabel(name: string) {
    return this.labels.get(name);
  }

  registerLabel(path: NodePath) {
    this.labels.set(path.node.label.name, path);
  }

  registerDeclaration(path: NodePath) {
    if (path.isLabeledStatement()) {
      this.registerLabel(path);
    } else if (path.isFunctionDeclaration()) {
      this.registerBinding("hoisted", path.get("id"), path);
    } else if (path.isVariableDeclaration()) {
      let declarations = path.get("declarations");
      for (let declar of (declarations: Array)) {
        this.registerBinding(path.node.kind, declar);
      }
    } else if (path.isClassDeclaration()) {
      this.registerBinding("let", path);
    } else if (path.isImportDeclaration()) {
      let specifiers = path.get("specifiers");
      for (let specifier of (specifiers: Array)) {
        this.registerBinding("module", specifier);
      }
    } else if (path.isExportDeclaration()) {
      let declar = path.get("declaration");
      if (declar.isClassDeclaration() || declar.isFunctionDeclaration() || declar.isVariableDeclaration()) {
        this.registerDeclaration(declar);
      }
    } else {
      this.registerBinding("unknown", path);
    }
  }

  buildUndefinedNode() {
    if (this.hasBinding("undefined")) {
      return t.unaryExpression("void", t.numericLiteral(0), true);
    } else {
      return t.identifier("undefined");
    }
  }

  registerConstantViolation(path: NodePath) {
    let ids = path.getBindingIdentifiers();
    for (let name in ids) {
      let binding = this.getBinding(name);
      if (binding) binding.reassign(path);
    }
  }

  registerBinding(kind: string, path: NodePath, bindingPath = path) {
    if (!kind) throw new ReferenceError("no `kind`");

    if (path.isVariableDeclaration()) {
      let declarators: Array<NodePath> = path.get("declarations");
      for (let declar of declarators) {
        this.registerBinding(kind, declar);
      }
      return;
    }

    let parent = this.getProgramParent();
    let ids = path.getBindingIdentifiers(true);

    for (let name in ids) {
      for (let id of (ids[name]: Array<Object>)) {
        let local = this.getOwnBinding(name);
        if (local) {
          // same identifier so continue safely as we're likely trying to register it
          // multiple times
          if (local.identifier === id) continue;

          this.checkBlockScopedCollisions(local, kind, name, id);
        }

        // It's erroneous that we currently consider flow a binding, however, we can't
        // remove it because people might be depending on it. See warning section
        // in `warnOnFlowBinding`.
        if (local && local.path.isFlow()) local = null;

        parent.references[name] = true;

        this.bindings[name] = new Binding({
          identifier: id,
          existing:   local,
          scope:      this,
          path:       bindingPath,
          kind:       kind
        });
      }
    }
  }

  addGlobal(node: Object) {
    this.globals[node.name] = node;
  }

  hasUid(name): boolean {
    let scope = this;

    do {
      if (scope.uids[name]) return true;
    } while (scope = scope.parent);

    return false;
  }

  hasGlobal(name: string): boolean {
    let scope = this;

    do {
      if (scope.globals[name]) return true;
    } while (scope = scope.parent);

    return false;
  }

  hasReference(name: string): boolean {
    let scope = this;

    do {
      if (scope.references[name]) return true;
    } while (scope = scope.parent);

    return false;
  }

  isPure(node, constantsOnly?: boolean) {
    if (t.isIdentifier(node)) {
      let binding = this.getBinding(node.name);
      if (!binding) return false;
      if (constantsOnly) return binding.constant;
      return true;
    } else if (t.isClass(node)) {
      if (node.superClass && !this.isPure(node.superClass, constantsOnly)) return false;
      return this.isPure(node.body, constantsOnly);
    } else if (t.isClassBody(node)) {
      for (let method of node.body) {
        if (!this.isPure(method, constantsOnly)) return false;
      }
      return true;
    } else if (t.isBinary(node)) {
      return this.isPure(node.left, constantsOnly) && this.isPure(node.right, constantsOnly);
    } else if (t.isArrayExpression(node)) {
      for (let elem of (node.elements: Array<Object>)) {
        if (!this.isPure(elem, constantsOnly)) return false;
      }
      return true;
    } else if (t.isObjectExpression(node)) {
      for (let prop of (node.properties: Array<Object>)) {
        if (!this.isPure(prop, constantsOnly)) return false;
      }
      return true;
    } else if (t.isClassMethod(node)) {
      if (node.computed && !this.isPure(node.key, constantsOnly)) return false;
      if (node.kind === "get" || node.kind === "set") return false;
      return true;
    } else if (t.isClassProperty(node) || t.isObjectProperty(node)) {
      if (node.computed && !this.isPure(node.key, constantsOnly)) return false;
      return this.isPure(node.value, constantsOnly);
    } else if (t.isUnaryExpression(node)) {
      return this.isPure(node.argument, constantsOnly);
    } else {
      return t.isPureish(node);
    }
  }

  /**
   * Set some arbitrary data on the current scope.
   */

  setData(key, val) {
    return this.data[key] = val;
  }

  /**
   * Recursively walk up scope tree looking for the data `key`.
   */

  getData(key) {
    let scope = this;
    do {
      let data = scope.data[key];
      if (data != null) return data;
    } while (scope = scope.parent);
  }

  /**
   * Recursively walk up scope tree looking for the data `key` and if it exists,
   * remove it.
   */

  removeData(key) {
    let scope = this;
    do {
      let data = scope.data[key];
      if (data != null) scope.data[key] = null;
    } while (scope = scope.parent);
  }

  init() {
    if (!this.references) this.crawl();
  }

  crawl() {
    _crawlCallsCount++;
    this._crawl();
    _crawlCallsCount--;
  }

  _crawl() {
    let path = this.path;

    //

    this.references = Object.create(null);
    this.bindings   = Object.create(null);
    this.globals    = Object.create(null);
    this.uids       = Object.create(null);
    this.data       = Object.create(null);

    // ForStatement - left, init

    if (path.isLoop()) {
      for (let key of (t.FOR_INIT_KEYS: Array<string>)) {
        let node = path.get(key);
        if (node.isBlockScoped()) this.registerBinding(node.node.kind, node);
      }
    }

    // FunctionExpression - id

    if (path.isFunctionExpression() && path.has("id")) {
      if (!path.get("id").node[t.NOT_LOCAL_BINDING]) {
        this.registerBinding("local", path.get("id"), path);
      }
    }

    // Class

    if (path.isClassExpression() && path.has("id")) {
      if (!path.get("id").node[t.NOT_LOCAL_BINDING]) {
        this.registerBinding("local", path);
      }
    }

    // Function - params, rest

    if (path.isFunction()) {
      let params: Array<NodePath> = path.get("params");
      for (let param of params) {
        this.registerBinding("param", param);
      }
    }

    // CatchClause - param

    if (path.isCatchClause()) {
      this.registerBinding("let", path);
    }

    // Program

    let parent = this.getProgramParent();
    if (parent.crawling) return;

    let state = {
      references: [],
      constantViolations: [],
      assignments: [],
    };

    this.crawling = true;
    path.traverse(collectorVisitor, state);
    this.crawling = false;

    // register assignments
    for (let path of state.assignments) {
      // register undeclared bindings as globals
      let ids = path.getBindingIdentifiers();
      let programParent;
      for (let name in ids) {
        if (path.scope.getBinding(name)) continue;

        programParent = programParent ||  path.scope.getProgramParent();
        programParent.addGlobal(ids[name]);
      }

      // register as constant violation
      path.scope.registerConstantViolation(path);
    }

    // register references
    for (let ref of state.references) {
      let binding = ref.scope.getBinding(ref.node.name);
      if (binding) {
        binding.reference(ref);
      } else {
        ref.scope.getProgramParent().addGlobal(ref.node);
      }
    }

    // register constant violations
    for (let path of state.constantViolations) {
      path.scope.registerConstantViolation(path);
    }
  }

  push(opts: {
    id: Object;
    init: ?Object;
    unique: ?boolean;
    _blockHoist: ?number;
    kind: "var" | "let";
  }) {
    let path = this.path;

    if (!path.isBlockStatement() && !path.isProgram()) {
      path = this.getBlockParent().path;
    }

    if (path.isSwitchStatement()) {
      path = this.getFunctionParent().path;
    }

    if (path.isLoop() || path.isCatchClause() || path.isFunction()) {
      t.ensureBlock(path.node);
      path = path.get("body");
    }

    let unique = opts.unique;
    let kind   = opts.kind || "var";
    let blockHoist = opts._blockHoist == null ? 2 : opts._blockHoist;

    let dataKey = `declaration:${kind}:${blockHoist}`;
    let declarPath  = !unique && path.getData(dataKey);

    if (!declarPath) {
      let declar = t.variableDeclaration(kind, []);
      declar._generated = true;
      declar._blockHoist = blockHoist;

      [declarPath] = path.unshiftContainer("body", [declar]);
      if (!unique) path.setData(dataKey, declarPath);
    }

    let declarator = t.variableDeclarator(opts.id, opts.init);
    declarPath.node.declarations.push(declarator);
    this.registerBinding(kind, declarPath.get("declarations").pop());
  }

  /**
   * Walk up to the top of the scope tree and get the `Program`.
   */

  getProgramParent() {
    let scope = this;
    do {
      if (scope.path.isProgram()) {
        return scope;
      }
    } while (scope = scope.parent);
    throw new Error("We couldn't find a Function or Program...");
  }

  /**
   * Walk up the scope tree until we hit either a Function or reach the
   * very top and hit Program.
   */

  getFunctionParent() {
    let scope = this;
    do {
      if (scope.path.isFunctionParent()) {
        return scope;
      }
    } while (scope = scope.parent);
    throw new Error("We couldn't find a Function or Program...");
  }

  /**
   * Walk up the scope tree until we hit either a BlockStatement/Loop/Program/Function/Switch or reach the
   * very top and hit Program.
   */

  getBlockParent() {
    let scope = this;
    do {
      if (scope.path.isBlockParent()) {
        return scope;
      }
    } while (scope = scope.parent);
    throw new Error("We couldn't find a BlockStatement, For, Switch, Function, Loop or Program...");
  }

  /**
   * Walks the scope tree and gathers **all** bindings.
   */

  getAllBindings(): Object {
    let ids = Object.create(null);

    let scope = this;
    do {
      defaults(ids, scope.bindings);
      scope = scope.parent;
    } while (scope);

    return ids;
  }

  /**
   * Walks the scope tree and gathers all declarations of `kind`.
   */

  getAllBindingsOfKind(): Object {
    let ids = Object.create(null);

    for (let kind of (arguments: Array)) {
      let scope = this;
      do {
        for (let name in scope.bindings) {
          let binding = scope.bindings[name];
          if (binding.kind === kind) ids[name] = binding;
        }
        scope = scope.parent;
      } while (scope);
    }

    return ids;
  }

  bindingIdentifierEquals(name: string, node: Object): boolean {
    return this.getBindingIdentifier(name) === node;
  }

  warnOnFlowBinding(binding) {
    if (_crawlCallsCount === 0 && binding && binding.path.isFlow()) {
      console.warn(`
        You or one of the Babel plugins you are using are using Flow declarations as bindings.
        Support for this will be removed in version 6.8. To find out the caller, grep for this
        message and change it to a \`console.trace()\`.
      `);
    }
    return binding;
  }

  getBinding(name: string) {
    let scope = this;

    do {
      let binding = scope.getOwnBinding(name);
      if (binding) return this.warnOnFlowBinding(binding);
    } while (scope = scope.parent);
  }

  getOwnBinding(name: string) {
    return this.warnOnFlowBinding(this.bindings[name]);
  }

  getBindingIdentifier(name: string) {
    let info = this.getBinding(name);
    return info && info.identifier;
  }

  getOwnBindingIdentifier(name: string) {
    let binding = this.bindings[name];
    return binding && binding.identifier;
  }

  hasOwnBinding(name: string) {
    return !!this.getOwnBinding(name);
  }

  hasBinding(name: string, noGlobals?) {
    if (!name) return false;
    if (this.hasOwnBinding(name)) return true;
    if (this.parentHasBinding(name, noGlobals)) return true;
    if (this.hasUid(name)) return true;
    if (!noGlobals && includes(Scope.globals, name)) return true;
    if (!noGlobals && includes(Scope.contextVariables, name)) return true;
    return false;
  }

  parentHasBinding(name: string, noGlobals?) {
    return this.parent && this.parent.hasBinding(name, noGlobals);
  }

  /**
   * Move a binding of `name` to another `scope`.
   */

  moveBindingTo(name, scope) {
    let info = this.getBinding(name);
    if (info) {
      info.scope.removeOwnBinding(name);
      info.scope = scope;
      scope.bindings[name] = info;
    }
  }

  removeOwnBinding(name: string) {
    delete this.bindings[name];
  }

  removeBinding(name: string) {
    // clear literal binding
    let info = this.getBinding(name);
    if (info) {
      info.scope.removeOwnBinding(name);
    }

    // clear uids with this name - https://github.com/babel/babel/issues/2101
    let scope = this;
    do {
      if (scope.uids[name]) {
        scope.uids[name] = false;
      }
    } while (scope = scope.parent);
  }
}