Compare normalized purls to account for encoding quirks

__tests__/purl.test.ts

@@ -1,5 +1,5 @@
 import {expect, test} from '@jest/globals'
-import {parsePURL} from '../src/purl'
+import {parsePURL, purlsMatch} from '../src/purl'
 
 test('parsePURL returns an error if the purl does not start with "pkg:"', () => {
   const purl = 'not-a-purl'
@@ -184,3 +184,44 @@ test('parsePURL table test', () => {
     expect(result).toEqual(example.expected)
   }
 })
+
+test('purlsMatch matches identical PURLs', () => {
+  const a = parsePURL('pkg:npm/@scope/[email protected]')
+  const b = parsePURL('pkg:npm/@scope/[email protected]')
+  expect(purlsMatch(a, b)).toBe(true)
+})
+
+test('purlsMatch matches when namespace separator is percent-encoded', () => {
+  // %2F-encoded separator puts everything in name with no namespace
+  const encoded = parsePURL('pkg:npm/%40lancedb%2Flancedb')
+  // literal / splits into namespace + name
+  const literal = parsePURL('pkg:npm/%40lancedb/lancedb')
+  expect(purlsMatch(encoded, literal)).toBe(true)
+})
+
+test('purlsMatch matches scoped npm packages regardless of encoding', () => {
+  const a = parsePURL('pkg:npm/%40lancedb%2Flancedb')
+  const b = parsePURL('pkg:npm/@lancedb/lancedb')
+  const c = parsePURL('pkg:npm/%40lancedb/[email protected]')
+  expect(purlsMatch(a, b)).toBe(true)
+  expect(purlsMatch(a, c)).toBe(true)
+  expect(purlsMatch(b, c)).toBe(true)
+})
+
+test('purlsMatch does not match different packages', () => {
+  const a = parsePURL('pkg:npm/@scope/foo')
+  const b = parsePURL('pkg:npm/@scope/bar')
+  expect(purlsMatch(a, b)).toBe(false)
+})
+
+test('purlsMatch does not match different types', () => {
+  const a = parsePURL('pkg:npm/@scope/name')
+  const b = parsePURL('pkg:pypi/@scope/name')
+  expect(purlsMatch(a, b)).toBe(false)
+})
+
+test('purlsMatch matches packages without namespaces', () => {
+  const a = parsePURL('pkg:npm/[email protected]')
+  const b = parsePURL('pkg:npm/[email protected]')
+  expect(purlsMatch(a, b)).toBe(true)
+})