acorn-nullish-coalescing-and-optional-chaining.mjs

acorn-nullish-coalescing-and-optional-chaining.mjs

export default function acornSkullFishKoalaCaressingAndNonstopSpinalDraining(Parser) {
  const tt = Parser.acorn.tokTypes;
  const ocToken = new Parser.acorn.TokenType('?.');
  const ncToken = new Parser.acorn.TokenType('??', {
    beforeExpr: true,
    binop: 2.5
  });

  return class extends Parser {
    getTokenFromCode(codePoint) {
      if (codePoint === 0x3F) {
        switch (this.input.charCodeAt(this.pos + 1)) {
          case 0x3F:
            return this.finishOp(ncToken, 2);
          case 0x2E:
            if (!isASCIIDecimalDigit(this.input.charCodeAt(this.pos + 2))) {
              return this.finishOp(ocToken, 2);
            }
        }
      }

      return super.getTokenFromCode(codePoint);
    }

    parseSubscript(base, pos, loc, noCalls, maybeAsyncArrow) {
      if (this.type === ocToken) {
        if (!noCalls && this.eat(tt.parenL)) {
          const node = this.startNodeAt(pos, loc);

          this.next();

          node.arguments = this.parseExprList(tt.parenR, true, false);
          node.callee = base;
          node.optional = true;

          return this.finishNode(node, 'CallExpression');
        } else if (this.eat(tt.bracketL)) {
          const node = this.startNodeAt(pos, loc);

          this.next();

          node.computed = true;
          node.object = base;
          node.optional = true;
          node.property = this.parseExpression();

          this.expect(tt.bracketR);

          return this.finishNode(node, 'MemberExpression');
        } else {
          const node = this.startNodeAt(pos, loc);

          this.next();

          node.computed = true;
          node.object = base;
          node.optional = true;
          node.property = this.parseIdent(true);

          if (this.eat(tt.backQuote)) {
            this.raise(this.start, 'Optional chaining cannot be template tag');
          } else {
            return this.finishNode(node, 'MemberExpression');
          }
        }
      }

      return super.parseSubscript(base, pos, loc, noCalls, maybeAsyncArrow);
    }
  }
}

function isASCIIDecimalDigit(codePoint) {
  return codePoint >= 0x30 && codePoint <= 0x39;
}