Parses a YAML file with unknown !ruby tags, using js-yaml

js-yaml-ruby-types.js

import { Type, Schema } from "js-yaml";

const BigDecimal = new Type("!ruby/object:BigDecimal", {
  kind: "scalar",
  construct: (data) => {
    return parseFloat(data.split(":")[1]);
  },
});

const supportedTags = [BigDecimal];
const supportedTagNames = supportedTags.map((type) => type.tag);

const createPassthroughTag = ({ tag, kind }) => new Type(tag, { kind });

const createSchema = (tags) => {
  return Schema.create([
    ...supportedTags,
    ...tags
      .filter(({ tag }) => !supportedTagNames.includes(tag))
      .map(createPassthroughTag),
  ]);
};

export const createSafeSchema = (message) => {
  const tags = Array.from(message.matchAll(/!ruby\/[A-Za-z: ]*/g), (m) => m[0]);
  const uniqueTags = Array.from(new Set(tags));

  return createSchema(
    uniqueTags.map((tag) => ({
      tag: tag.replace("\n", "").trim(),
      kind: tag.endsWith(" ") ? "scalar" : "mapping",
    }))
  );
};