improve hashing (#56)

Author: samwillis

packages/d2ts/src/utils.ts

@@ -72,17 +72,46 @@ export function chunkedArrayPush(array: unknown[], other: unknown[]) {
 
 const hashCache = new WeakMap()
 
+/**
+ * Replacer function for JSON.stringify that converts unsupported types to strings
+ */
+function hashReplacer(_key: string, value: any): any {
+  if (typeof value === 'bigint') {
+    return String(value)
+  } else if (typeof value === 'symbol') {
+    return String(value)
+  } else if (typeof value === 'function') {
+    return String(value)
+  } else if (value === undefined) {
+    return 'undefined'
+  } else if (value instanceof Map) {
+    return `Map(${JSON.stringify(Array.from(value.entries()), hashReplacer)})`
+  } else if (value instanceof Set) {
+    return `Set(${JSON.stringify(Array.from(value.values()), hashReplacer)})`
+  }
+  return value
+}
+
 /**
  * A hash method that caches the hash of a value in a week map
  */
 export function hash(data: any): string | number {
-  if (data === null || data === undefined || typeof data !== 'object') {
-    return JSON.stringify(data)
+  if (
+    data === null ||
+    data === undefined ||
+    (typeof data !== 'object' && typeof data !== 'function')
+  ) {
+    // Can't be cached in the weak map because it's not an object
+    const serialized = JSON.stringify(data, hashReplacer)
+    return murmurhash.murmur3(serialized)
   }
 
   if (hashCache.has(data)) {
     return hashCache.get(data)
   }
 
-  return murmurhash.murmur3(JSON.stringify(JSON.stringify(data)))
+  const serialized = JSON.stringify(data, hashReplacer)
+  const hashValue = murmurhash.murmur3(JSON.stringify(serialized))
+  hashCache.set(data, hashValue)
+  return hashValue
 }

packages/d2ts/tests/utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest'
-import { DefaultMap, WeakRefMap } from '../src/utils.js'
+import { DefaultMap, WeakRefMap, hash } from '../src/utils.js'
 
 describe('DefaultMap', () => {
   it('should return default value for missing keys', () => {
@@ -76,3 +76,321 @@ describe('WeakRefMap', () => {
   //   }
   // })
 })
+
+describe('hash', () => {
+  describe('primitive types', () => {
+    it('should hash null', () => {
+      const result = hash(null)
+      expect(typeof result).toBe('number')
+    })
+
+    it('should hash undefined', () => {
+      const result = hash(undefined)
+      expect(typeof result).toBe('number')
+    })
+
+    it('should hash strings', () => {
+      const result1 = hash('hello')
+      const result2 = hash('')
+      const result3 = hash('test with spaces')
+      const result4 = hash('special\nchars\t"')
+      
+      expect(typeof result1).toBe('number')
+      expect(typeof result2).toBe('number')
+      expect(typeof result3).toBe('number')
+      expect(typeof result4).toBe('number')
+      
+      // Same strings should have same hash
+      expect(hash('hello')).toBe(result1)
+    })
+
+    it('should hash numbers', () => {
+      const result1 = hash(42)
+      const result2 = hash(0)
+      const result3 = hash(-1)
+      const result4 = hash(3.14159)
+      const result5 = hash(Infinity)
+      const result6 = hash(-Infinity)
+      const result7 = hash(NaN)
+      
+      expect(typeof result1).toBe('number')
+      expect(typeof result2).toBe('number')
+      expect(typeof result3).toBe('number')
+      expect(typeof result4).toBe('number')
+      expect(typeof result5).toBe('number')
+      expect(typeof result6).toBe('number')
+      expect(typeof result7).toBe('number')
+      
+      // Same numbers should have same hash
+      expect(hash(42)).toBe(result1)
+    })
+
+    it('should hash booleans', () => {
+      const result1 = hash(true)
+      const result2 = hash(false)
+      
+      expect(typeof result1).toBe('number')
+      expect(typeof result2).toBe('number')
+      expect(result1).not.toBe(result2)
+      
+      // Same booleans should have same hash
+      expect(hash(true)).toBe(result1)
+      expect(hash(false)).toBe(result2)
+    })
+
+    it('should hash bigint', () => {
+      const result1 = hash(123n)
+      const result2 = hash(456n)
+      const result3 = hash(123n)
+      
+      expect(typeof result1).toBe('number')
+      expect(typeof result2).toBe('number')
+      expect(typeof result3).toBe('number')
+      expect(result1).toBe(result3) // Same bigint should have same hash
+      expect(result1).not.toBe(result2) // Different bigints should have different hash
+    })
+
+    it('should hash symbols', () => {
+      const sym1 = Symbol('test')
+      const sym2 = Symbol('test')
+      const sym3 = Symbol('different')
+      
+      const result1 = hash(sym1)
+      const result2 = hash(sym2)
+      const result3 = hash(sym3)
+      
+      expect(typeof result1).toBe('number')
+      expect(typeof result2).toBe('number')
+      expect(typeof result3).toBe('number')
+      // Note: Different symbol instances with same description have same string representation
+      expect(result1).toBe(result2)
+      expect(result1).not.toBe(result3)
+    })
+  })
+
+  describe('object types', () => {
+    it('should hash plain objects', () => {
+      const obj1 = { a: 1, b: 2 }
+      const obj2 = { b: 2, a: 1 } // Different key order
+      
+      const hash1 = hash(obj1)
+      const hash2 = hash(obj2)
+      
+      expect(typeof hash1).toBe('number')
+      expect(typeof hash2).toBe('number')
+      // Note: Different key orders might produce different hashes depending on JSON.stringify behavior
+    })
+
+    it('should hash arrays', () => {
+      const arr1 = [1, 2, 3]
+      const arr2 = [1, 2, 3]
+      const arr3 = [3, 2, 1]
+      
+      const hash1 = hash(arr1)
+      const hash2 = hash(arr2)
+      const hash3 = hash(arr3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same content should have same hash
+      expect(hash1).not.toBe(hash3) // Different content should have different hash
+    })
+
+    it('should hash Date objects', () => {
+      const date1 = new Date('2023-01-01')
+      const date2 = new Date('2023-01-01')
+      const date3 = new Date('2023-01-02')
+      
+      const hash1 = hash(date1)
+      const hash2 = hash(date2)
+      const hash3 = hash(date3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same date should have same hash
+      expect(hash1).not.toBe(hash3) // Different dates should have different hash
+    })
+
+    it('should hash RegExp objects', () => {
+      const regex1 = /test/g
+      const regex2 = /test/g
+      const regex3 = /different/i
+      
+      const hash1 = hash(regex1)
+      const hash2 = hash(regex2)
+      const hash3 = hash(regex3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same regex should have same hash
+      // Note: RegExp objects serialize to empty objects {}, so they all produce the same hash
+      expect(hash1).toBe(hash3) // All RegExp objects have the same hash
+    })
+
+    it('should hash nested objects', () => {
+      const nested1 = { a: { b: { c: 1 } } }
+      const nested2 = { a: { b: { c: 1 } } }
+      const nested3 = { a: { b: { c: 2 } } }
+      
+      const hash1 = hash(nested1)
+      const hash2 = hash(nested2)
+      const hash3 = hash(nested3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2)
+      expect(hash1).not.toBe(hash3)
+    })
+
+    it('should hash functions', () => {
+      const func1 = function test() { return 1 }
+      const func2 = function test() { return 1 }
+      const func3 = function different() { return 2 }
+      
+      const hash1 = hash(func1)
+      const hash2 = hash(func2)
+      const hash3 = hash(func3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(typeof hash2).toBe('number')
+      expect(typeof hash3).toBe('number')
+      expect(hash1).toBe(hash2) // Same function definition should have same hash
+      expect(hash1).not.toBe(hash3) // Different function should have different hash
+    })
+
+    it('should hash Set objects', () => {
+      const set1 = new Set([1, 2, 3])
+      const set2 = new Set([1, 2, 3])
+      const set3 = new Set([1, 2, 3, 4])
+      
+      const hash1 = hash(set1)
+      const hash2 = hash(set2)
+      const hash3 = hash(set3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same content should have same hash
+      expect(hash1).not.toBe(hash3) // Different content should have different hash
+    })
+
+    it('should hash Map objects', () => {
+      const map1 = new Map([['a', 1], ['b', 2]])
+      const map2 = new Map([['a', 1], ['b', 2]])
+      const map3 = new Map([['a', 1], ['b', 2], ['c', 3]])
+      
+      const hash1 = hash(map1)
+      const hash2 = hash(map2)
+      const hash3 = hash(map3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same content should have same hash
+      expect(hash1).not.toBe(hash3) // Different content should have different hash
+    })
+
+    it('should hash Maps and Sets with unsupported types', () => {
+      // Map with BigInt values
+      const mapWithBigInt1 = new Map([['a', 123n], ['b', 456n]])
+      const mapWithBigInt2 = new Map([['a', 123n], ['b', 456n]])
+      const mapWithBigInt3 = new Map([['a', 123n], ['b', 789n]])
+      
+      const hash1 = hash(mapWithBigInt1)
+      const hash2 = hash(mapWithBigInt2)
+      const hash3 = hash(mapWithBigInt3)
+      
+      expect(typeof hash1).toBe('number')
+      expect(hash1).toBe(hash2) // Same BigInt content should have same hash
+      expect(hash1).not.toBe(hash3) // Different BigInt content should have different hash
+      
+      // Set with Symbol values
+      const sym1 = Symbol('test')
+      const sym2 = Symbol('different')
+      const setWithSymbols1 = new Set([sym1, sym2])
+      const setWithSymbols2 = new Set([sym1, sym2])
+      const setWithSymbols3 = new Set([sym1])
+      
+      const hash4 = hash(setWithSymbols1)
+      const hash5 = hash(setWithSymbols2)
+      const hash6 = hash(setWithSymbols3)
+      
+      expect(typeof hash4).toBe('number')
+      expect(hash4).toBe(hash5) // Same Symbol content should have same hash
+      expect(hash4).not.toBe(hash6) // Different Symbol content should have different hash
+    })
+  })
+
+  describe('caching behavior', () => {
+    it('should cache hash values for objects', () => {
+      const obj = { test: 'value' }
+      
+      const hash1 = hash(obj)
+      const hash2 = hash(obj)
+      
+      expect(hash1).toBe(hash2)
+      expect(typeof hash1).toBe('number')
+    })
+
+    it('should return cached values on subsequent calls', () => {
+      const obj = { complex: { nested: { data: [1, 2, 3] } } }
+      
+      // First call should compute and cache
+      const hash1 = hash(obj)
+      
+      // Second call should return cached value
+      const hash2 = hash(obj)
+      
+      expect(hash1).toBe(hash2)
+      expect(typeof hash1).toBe('number')
+    })
+
+    it('should not cache primitive values', () => {
+      // Primitives should not be cached as they use JSON.stringify directly
+      const hash1 = hash('test')
+      const hash2 = hash('test')
+      
+      expect(hash1).toBe(hash2)
+      expect(typeof hash1).toBe('number')
+    })
+  })
+
+  describe('edge cases', () => {
+    it('should handle empty objects and arrays', () => {
+      expect(typeof hash({})).toBe('number')
+      expect(typeof hash([])).toBe('number')
+      expect(hash({})).not.toBe(hash([]))
+    })
+
+    it('should handle objects with null and undefined values', () => {
+      const obj1 = { a: null, b: undefined }
+      const obj2 = { a: null, b: undefined }
+      
+      const hash1 = hash(obj1)
+      const hash2 = hash(obj2)
+      
+      expect(hash1).toBe(hash2)
+      expect(typeof hash1).toBe('number')
+    })
+
+    it('should handle mixed type arrays', () => {
+      const mixedArray = [1, 'string', true, null, { key: 'value' }]
+      const sameArray = [1, 'string', true, null, { key: 'value' }]
+      
+      const hash1 = hash(mixedArray)
+      const hash2 = hash(sameArray)
+      
+      expect(hash1).toBe(hash2)
+      expect(typeof hash1).toBe('number')
+    })
+
+    it('should produce consistent hashes for same content', () => {
+      const obj = { 
+        string: 'test',
+        number: 42,
+        boolean: true,
+        array: [1, 2, 3],
+        nested: { inner: 'value' }
+      }
+      
+      // Multiple calls should return the same hash
+      const hashes = Array.from({ length: 5 }, () => hash(obj))
+      const firstHash = hashes[0]
+      
+      expect(hashes.every(h => h === firstHash)).toBe(true)
+      expect(typeof firstHash).toBe('number')
+    })
+  })
+})