Linvail

Linvail is a npm module which provides provenancial equality to JavaScript. JavaScript as many other languages provides two kinds of equality: structural equality which compares values based on their content and referential equality which compare value based on their memory location. Provenancial equality goes a step further and compares values based on their provenance. Provenancial equality can be seen as a stricter version of referential equality which is itself a stricter version of structural equality. In other words, the following implication holds:

x eq_prov y  => x eq_ref y => x eq_struct y

npx linvail main.mjs

import { is } from "linvail";
const foo = 123;
const bar = 456;
const array = [bar, foo];
array.sort();
console.log(array[0]); // 123
console.log(array[1]); // 456
console.log(is(array[0], foo)); // true
console.log(is(array[0], 123)); // false

CLI

Configuration options can be passed to the CLI using environment variables:

• LINVAIL_INCLUDE: A comma-separated list of globs to designate the files where data povenance should be tracked. Default: "**/*".
• LINVAIL_EXCLUDE: A comma-separated list of globs to designate the files where data provenance should not be tracked; takes precedence over LINVAIL_INCLUDE. Default: "node_modules/**/*".
• LINVAIL_GLOBAL_OBJECT: Defines whether data provenance should be tracked across the global object and the global declarative record. Default: "external".
  • "external": Leave the global object and the global declarative intact.
  • "internal": Replace the global object and the global declarative record with new objects that can track data provenance.
• LINVAIL_GLOBAL_DYNAMIC_CODE: Defines whether data provenance should be tracked across global dynamic code. Note that data provenance is always tracked across local dynamic code (i.e.: strings passed to direct eval calls). Default: "internal".

API

types

• is(value1, value2): Provenancial equality.
• dir(value): Bypass the access control system and log the value to the console.
• Set, Map, WeakSet, and WeakMap: Similar to their standard counter part but keys are compared using provenancial equality.

  import { Set } from "linvail";
  const foo = 123;
  const set = new Set([foo]);
  console.log(set.has(foo)); // true
  console.log(set.has(123)); // false