chevrotain/src/parse/grammar/resolver.ts

Chevrotain is a high performance fault tolerant javascript parsing DSL for building recursive decent parsers

import {
  IParserUnresolvedRefDefinitionError,
  ParserDefinitionErrorType,
} from "../parser/parser.js";
import { forEach, values } from "lodash-es";
import { GAstVisitor, NonTerminal, Rule } from "@chevrotain/gast";
import {
  IGrammarResolverErrorMessageProvider,
  IParserDefinitionError,
} from "./types.js";

export function resolveGrammar(
  topLevels: Record<string, Rule>,
  errMsgProvider: IGrammarResolverErrorMessageProvider,
): IParserDefinitionError[] {
  const refResolver = new GastRefResolverVisitor(topLevels, errMsgProvider);
  refResolver.resolveRefs();
  return refResolver.errors;
}

export class GastRefResolverVisitor extends GAstVisitor {
  public errors: IParserUnresolvedRefDefinitionError[] = [];
  private currTopLevel: Rule;

  constructor(
    private nameToTopRule: Record<string, Rule>,
    private errMsgProvider: IGrammarResolverErrorMessageProvider,
  ) {
    super();
  }

  public resolveRefs(): void {
    forEach(values(this.nameToTopRule), (prod) => {
      this.currTopLevel = prod;
      prod.accept(this);
    });
  }

  public visitNonTerminal(node: NonTerminal): void {
    const ref = this.nameToTopRule[node.nonTerminalName];

    if (!ref) {
      const msg = this.errMsgProvider.buildRuleNotFoundError(
        this.currTopLevel,
        node,
      );
      this.errors.push({
        message: msg,
        type: ParserDefinitionErrorType.UNRESOLVED_SUBRULE_REF,
        ruleName: this.currTopLevel.name,
        unresolvedRefName: node.nonTerminalName,
      });
    } else {
      node.referencedRule = ref;
    }
  }
}