util.js

// @flow

import { indexes, type Position } from "../util/location";
import {
  tokenIsLiteralPropertyName,
  tokenLabelName,
  tt,
  type TokenType,
} from "../tokenizer/types";
import Tokenizer from "../tokenizer";
import State from "../tokenizer/state";
import type { Node } from "../types";
import { lineBreak, skipWhiteSpaceToLineBreak } from "../util/whitespace";
import { isIdentifierChar } from "../util/identifier";
import ClassScopeHandler from "../util/class-scope";
import ExpressionScopeHandler from "../util/expression-scope";
import { SCOPE_PROGRAM } from "../util/scopeflags";
import ProductionParameterHandler, {
  PARAM_AWAIT,
  PARAM,
} from "../util/production-parameter";
import { Errors, type ErrorTemplate, ErrorCodes } from "./error";
import type { ParsingError } from "./error";
import type { PluginConfig } from "./base";
/*::
import type ScopeHandler from "../util/scope";
*/

type TryParse<Node, Error, Thrown, Aborted, FailState> = {
  node: Node,
  error: Error,
  thrown: Thrown,
  aborted: Aborted,
  failState: FailState,
};

// ## Parser utilities

export default class UtilParser extends Tokenizer {
  // Forward-declaration: defined in parser/index.js
  /*::
  +getScopeHandler: () => Class<ScopeHandler<*>>;
  */

  // TODO

  addExtra(
    node: Node,
    key: string,
    value: any,
    enumerable: boolean = true,
  ): void {
    if (!node) return;

    const extra = (node.extra = node.extra || {});
    if (enumerable) {
      extra[key] = value;
    } else {
      Object.defineProperty(extra, key, { enumerable, value });
    }
  }

  // Tests whether parsed token is a contextual keyword.

  isContextual(token: TokenType): boolean {
    return this.state.type === token && !this.state.containsEsc;
  }

  isUnparsedContextual(nameStart: number, name: string): boolean {
    const nameEnd = nameStart + name.length;
    if (this.input.slice(nameStart, nameEnd) === name) {
      const nextCh = this.input.charCodeAt(nameEnd);
      return !(
        isIdentifierChar(nextCh) ||
        // check if `nextCh is between 0xd800 - 0xdbff,
        // if `nextCh` is NaN, `NaN & 0xfc00` is 0, the function
        // returns true
        (nextCh & 0xfc00) === 0xd800
      );
    }
    return false;
  }

  isLookaheadContextual(name: string): boolean {
    const next = this.nextTokenStart();
    return this.isUnparsedContextual(next, name);
  }

  // Consumes contextual keyword if possible.

  eatContextual(token: TokenType): boolean {
    if (this.isContextual(token)) {
      this.next();
      return true;
    }
    return false;
  }

  // Asserts that following token is given contextual keyword.

  expectContextual(token: TokenType, template?: ErrorTemplate): void {
    if (!this.eatContextual(token)) {
      if (template != null) {
        /* eslint-disable @babel/development-internal/dry-error-messages */
        throw this.raise(template, { at: this.state.startLoc });
      }
      throw this.unexpected(null, token);
    }
  }

  // Test whether a semicolon can be inserted at the current position.

  canInsertSemicolon(): boolean {
    return (
      this.match(tt.eof) ||
      this.match(tt.braceR) ||
      this.hasPrecedingLineBreak()
    );
  }

  hasPrecedingLineBreak(): boolean {
    return lineBreak.test(
      this.input.slice(indexes.get(this.state.lastTokEndLoc), this.state.start),
    );
  }

  hasFollowingLineBreak(): boolean {
    skipWhiteSpaceToLineBreak.lastIndex = this.state.end;
    return skipWhiteSpaceToLineBreak.test(this.input);
  }

  // TODO

  isLineTerminator(): boolean {
    return this.eat(tt.semi) || this.canInsertSemicolon();
  }

  // Consume a semicolon, or, failing that, see if we are allowed to
  // pretend that there is a semicolon at this position.

  semicolon(allowAsi: boolean = true): void {
    if (allowAsi ? this.isLineTerminator() : this.eat(tt.semi)) return;
    this.raise(Errors.MissingSemicolon, { at: this.state.lastTokEndLoc });
  }

  // Expect a token of a given type. If found, consume it, otherwise,
  // raise an unexpected token error at given pos.

  expect(type: TokenType, loc?: ?Position): void {
    this.eat(type) || this.unexpected(loc, type);
  }

  // Throws if the current token and the prev one are separated by a space.
  assertNoSpace(message: string = "Unexpected space."): void {
    // $FlowIgnore[incompatible-type] We know this exists, so it can't be undefined.
    if (this.state.start > indexes.get(this.state.lastTokEndLoc)) {
      /* eslint-disable @babel/development-internal/dry-error-messages */
      this.raise(
        {
          code: ErrorCodes.SyntaxError,
          reasonCode: "UnexpectedSpace",
          template: message,
        },
        { at: this.state.lastTokEndLoc },
        /* eslint-enable @babel/development-internal/dry-error-messages */
      );
    }
  }

  // Raise an unexpected token error. Can take the expected token type
  // instead of a message string.

  unexpected(loc?: ?Position, type?: ?TokenType): empty {
    /* eslint-disable @babel/development-internal/dry-error-messages */
    throw this.raise(
      {
        code: ErrorCodes.SyntaxError,
        reasonCode: "UnexpectedToken",
        template:
          type != null
            ? `Unexpected token, expected "${tokenLabelName(type)}"`
            : "Unexpected token",
      },
      { at: loc != null ? loc : this.state.startLoc },
    );
    /* eslint-enable @babel/development-internal/dry-error-messages */
  }

  getPluginNamesFromConfigs(pluginConfigs: Array<PluginConfig>): Array<string> {
    return pluginConfigs.map(c => {
      if (typeof c === "string") {
        return c;
      } else {
        return c[0];
      }
    });
  }

  expectPlugin(pluginConfig: PluginConfig, loc?: ?Position): true {
    if (!this.hasPlugin(pluginConfig)) {
      throw this.raiseWithData(
        loc != null ? loc : this.state.startLoc,
        { missingPlugin: this.getPluginNamesFromConfigs([pluginConfig]) },
        `This experimental syntax requires enabling the parser plugin: ${JSON.stringify(
          pluginConfig,
        )}.`,
      );
    }

    return true;
  }

  expectOnePlugin(pluginConfigs: Array<PluginConfig>): void {
    if (!pluginConfigs.some(c => this.hasPlugin(c))) {
      throw this.raiseWithData(
        this.state.startLoc,
        { missingPlugin: this.getPluginNamesFromConfigs(pluginConfigs) },
        `This experimental syntax requires enabling one of the following parser plugin(s): ${pluginConfigs
          .map(c => JSON.stringify(c))
          .join(", ")}.`,
      );
    }
  }

  // tryParse will clone parser state.
  // It is expensive and should be used with cautions
  tryParse<T: Node | $ReadOnlyArray<Node>>(
    fn: (abort: (node?: T) => empty) => T,
    oldState: State = this.state.clone(),
  ):
    | TryParse<T, null, false, false, null>
    | TryParse<T | null, ParsingError, boolean, false, State>
    | TryParse<T | null, null, false, true, State> {
    const abortSignal: { node: T | null } = { node: null };
    try {
      const node = fn((node = null) => {
        abortSignal.node = node;
        throw abortSignal;
      });
      if (this.state.errors.length > oldState.errors.length) {
        const failState = this.state;
        this.state = oldState;
        // tokensLength should be preserved during error recovery mode
        // since the parser does not halt and will instead parse the
        // remaining tokens
        this.state.tokensLength = failState.tokensLength;
        return {
          node,
          error: (failState.errors[oldState.errors.length]: ParsingError),
          thrown: false,
          aborted: false,
          failState,
        };
      }

      return {
        node,
        error: null,
        thrown: false,
        aborted: false,
        failState: null,
      };
    } catch (error) {
      const failState = this.state;
      this.state = oldState;
      if (error instanceof SyntaxError) {
        return { node: null, error, thrown: true, aborted: false, failState };
      }
      if (error === abortSignal) {
        return {
          node: abortSignal.node,
          error: null,
          thrown: false,
          aborted: true,
          failState,
        };
      }

      throw error;
    }
  }

  checkExpressionErrors(
    refExpressionErrors: ?ExpressionErrors,
    andThrow: boolean,
  ): void {
    if (!andThrow || !refExpressionErrors) {
      return;
    }

    const { shorthandAssignLoc, doubleProtoLoc, optionalParametersLoc } =
      refExpressionErrors;

    if (shorthandAssignLoc != null) {
      this.raise(Errors.InvalidCoverInitializedName, {
        at: shorthandAssignLoc,
      });
    }

    if (doubleProtoLoc != null) {
      this.raise(Errors.DuplicateProto, { at: doubleProtoLoc });
    }

    if (optionalParametersLoc != null) {
      this.unexpected(optionalParametersLoc);
    }
  }

  /**
   * Test if current token is a literal property name
   * https://tc39.es/ecma262/#prod-LiteralPropertyName
   * LiteralPropertyName:
   *   IdentifierName
   *   StringLiteral
   *   NumericLiteral
   *   BigIntLiteral
   */
  isLiteralPropertyName(): boolean {
    return tokenIsLiteralPropertyName(this.state.type);
  }

  /*
   * Test if given node is a PrivateName
   * will be overridden in ESTree plugin
   */
  isPrivateName(node: Node): boolean {
    return node.type === "PrivateName";
  }

  /*
   * Return the string value of a given private name
   * WITHOUT `#`
   * @see {@link https://tc39.es/ecma262/#sec-static-semantics-stringvalue}
   */
  getPrivateNameSV(node: Node): string {
    return node.id.name;
  }

  /*
   * Return whether the given node is a member/optional chain that
   * contains a private name as its property
   * It is overridden in ESTree plugin
   */
  hasPropertyAsPrivateName(node: Node): boolean {
    return (
      (node.type === "MemberExpression" ||
        node.type === "OptionalMemberExpression") &&
      this.isPrivateName(node.property)
    );
  }

  isOptionalChain(node: Node): boolean {
    return (
      node.type === "OptionalMemberExpression" ||
      node.type === "OptionalCallExpression"
    );
  }

  isObjectProperty(node: Node): boolean {
    return node.type === "ObjectProperty";
  }

  isObjectMethod(node: Node): boolean {
    return node.type === "ObjectMethod";
  }

  initializeScopes(
    inModule: boolean = this.options.sourceType === "module",
  ): () => void {
    // Initialize state
    const oldLabels = this.state.labels;
    this.state.labels = [];

    const oldExportedIdentifiers = this.exportedIdentifiers;
    this.exportedIdentifiers = new Set();

    // initialize scopes
    const oldInModule = this.inModule;
    this.inModule = inModule;

    const oldScope = this.scope;
    const ScopeHandler = this.getScopeHandler();
    this.scope = new ScopeHandler(this.raise.bind(this), this.inModule);

    const oldProdParam = this.prodParam;
    this.prodParam = new ProductionParameterHandler();

    const oldClassScope = this.classScope;
    this.classScope = new ClassScopeHandler(this.raise.bind(this));

    const oldExpressionScope = this.expressionScope;
    this.expressionScope = new ExpressionScopeHandler(this.raise.bind(this));

    return () => {
      // Revert state
      this.state.labels = oldLabels;
      this.exportedIdentifiers = oldExportedIdentifiers;

      // Revert scopes
      this.inModule = oldInModule;
      this.scope = oldScope;
      this.prodParam = oldProdParam;
      this.classScope = oldClassScope;
      this.expressionScope = oldExpressionScope;
    };
  }

  enterInitialScopes() {
    let paramFlags = PARAM;
    if (this.inModule) {
      paramFlags |= PARAM_AWAIT;
    }
    this.scope.enter(SCOPE_PROGRAM);
    this.prodParam.enter(paramFlags);
  }
}

/**
 * The ExpressionErrors is a context struct used to track ambiguous patterns
 * When we are sure the parsed pattern is a RHS, which means it is not a pattern,
 * we will throw on this position on invalid assign syntax, otherwise it will be reset to -1
 *
 * Types of ExpressionErrors:
 *
 * - **shorthandAssignLoc**: track initializer `=` position
 * - **doubleProtoLoc**: track the duplicate `__proto__` key position
 * - **optionalParametersLoc**: track the optional paramter (`?`).
 * It's only used by typescript and flow plugins
 */
export class ExpressionErrors {
  shorthandAssignLoc: ?Position = null;
  doubleProtoLoc: ?Position = null;
  optionalParametersLoc: ?Position = null;
}