🎨 [PANA-5260] Consolidate recorder object id tracking code (#4049)

Author: sethfowler-datadog

packages/rum/src/domain/record/eventIds.ts

@@ -7,8 +7,6 @@ import type { ShadowRootsController } from './shadowRootsController'
 import type { RecordingScope } from './recordingScope'
 import { createRecordingScope } from './recordingScope'
 import { createElementsScrollPositions } from './elementsScrollPositions'
-import { createEventIds } from './eventIds'
-import { createNodeIds } from './nodeIds'
 import type { EmitRecordCallback } from './record.types'
 import type { SerializationTransaction } from './serialization'
 import { SerializationKind, serializeInTransaction, serializeNode } from './serialization'
@@ -76,8 +74,6 @@ function createTemporaryRecordingScope(configuration?: Partial<RumConfiguration>
       ...configuration,
     } as RumConfiguration,
     createElementsScrollPositions(),
-    createEventIds(),
-    createNodeIds(),
     {
       addShadowRoot: noop,
       removeShadowRoot: noop,

packages/rum/src/domain/record/internalApi.ts

@@ -0,0 +1,126 @@
+import type { EventId, ItemIds, NodeId, StringId, StyleSheetId } from './itemIds'
+import {
+  createEventIds,
+  createNodeIds,
+  createStringIds,
+  createStyleSheetIds,
+  EventIdConstants,
+  NodeIdConstants,
+  StringIdConstants,
+  StyleSheetIdConstants,
+} from './itemIds'
+
+describe('ItemIds', () => {
+  const describeItemIdVariant = <ItemType, ItemId extends number>(
+    name: string,
+    createIdMap: () => ItemIds<ItemType, ItemId>,
+    createItem: () => ItemType,
+    firstId: ItemId
+  ) => {
+    describe(name, () => {
+      let itemIds = createIdMap()
+
+      beforeEach(() => {
+        itemIds = createIdMap()
+      })
+
+      describe('clear', () => {
+        it('removes all id mappings', () => {
+          const item = createItem()
+          itemIds.getOrInsert(item)
+          expect(itemIds.get(item)).toBe(firstId)
+
+          itemIds.clear()
+          expect(itemIds.get(item)).toBeUndefined()
+        })
+
+        it('restarts the id sequence', () => {
+          for (let id = firstId; id < firstId + 3; id++) {
+            const item = createItem()
+            expect(itemIds.getOrInsert(item)).toBe(id)
+            expect(itemIds.getOrInsert(item)).toBe(id)
+          }
+
+          itemIds.clear()
+
+          for (let id = firstId; id < firstId + 3; id++) {
+            const item = createItem()
+            expect(itemIds.getOrInsert(item)).toBe(id)
+            expect(itemIds.getOrInsert(item)).toBe(id)
+          }
+        })
+      })
+
+      describe('get', () => {
+        it('returns undefined for items that have not been assigned an id', () => {
+          expect(itemIds.get(createItem())).toBe(undefined)
+        })
+
+        it('returns the assigned id if one exists', () => {
+          const item = createItem()
+          itemIds.getOrInsert(item)
+          expect(itemIds.get(item)).toBe(firstId)
+        })
+      })
+
+      describe('getOrInsert', () => {
+        it('assigns ids in order', () => {
+          for (let id = firstId; id < firstId + 3; id++) {
+            const item = createItem()
+            expect(itemIds.getOrInsert(item)).toBe(id)
+            expect(itemIds.getOrInsert(item)).toBe(id)
+          }
+        })
+
+        it('reuses any existing id', () => {
+          itemIds.getOrInsert(createItem())
+          itemIds.getOrInsert(createItem())
+          const item = createItem()
+          const itemId = itemIds.getOrInsert(item)
+          expect(itemIds.getOrInsert(item)).toBe(itemId)
+          expect(itemIds.get(item)).toBe(itemId)
+        })
+      })
+
+      describe('size', () => {
+        it('increments when an id is assigned', () => {
+          expect(itemIds.size).toBe(0)
+          itemIds.getOrInsert(createItem())
+          expect(itemIds.size).toBe(1)
+          itemIds.getOrInsert(createItem())
+          expect(itemIds.size).toBe(2)
+        })
+      })
+    })
+  }
+
+  describeItemIdVariant(
+    'EventIds',
+    createEventIds,
+    () => new Event('someCustomEvent'),
+    EventIdConstants.FIRST_ID as EventId
+  )
+
+  describeItemIdVariant(
+    'NodeIds',
+    createNodeIds,
+    () => document.createElement('div'),
+    NodeIdConstants.FIRST_ID as NodeId
+  )
+
+  let nextString = 0
+  describeItemIdVariant(
+    'StringIds',
+    createStringIds,
+    () => `string${nextString++}`,
+    StringIdConstants.FIRST_ID as StringId
+  )
+
+  describeItemIdVariant(
+    'StyleSheetIds',
+    createStyleSheetIds,
+    // The CSSStyleSheet constructor is not available on older browsers.
+    () => ({ type: 'CSSStyleSheet' }),
+    StyleSheetIdConstants.FIRST_ID as StyleSheetId
+  )
+})

packages/rum/src/domain/record/itemIds.spec.ts

@@ -0,0 +1,85 @@
+export type EventId = number & { __brand: 'EventId' }
+export type EventIds = ItemIds<Event, EventId>
+export const enum EventIdConstants {
+  FIRST_ID = 1,
+}
+export function createEventIds(): EventIds {
+  return createWeakIdMap(EventIdConstants.FIRST_ID as EventId)
+}
+
+export type NodeId = number & { __brand: 'NodeId' }
+export type NodeIds = ItemIds<Node, NodeId>
+export const enum NodeIdConstants {
+  FIRST_ID = 0,
+}
+export function createNodeIds(): NodeIds {
+  return createWeakIdMap(NodeIdConstants.FIRST_ID as NodeId)
+}
+
+export type StringId = number & { __brand: 'StringId' }
+export type StringIds = ItemIds<string, StringId>
+export const enum StringIdConstants {
+  FIRST_ID = 0,
+}
+export function createStringIds(): StringIds {
+  return createIdMap(StringIdConstants.FIRST_ID as StringId)
+}
+
+export type StyleSheetId = number & { __brand: 'StyleSheetId' }
+export type StyleSheetIds = ItemIds<CSSStyleSheet, StyleSheetId>
+export const enum StyleSheetIdConstants {
+  FIRST_ID = 0,
+}
+export function createStyleSheetIds(): StyleSheetIds {
+  return createWeakIdMap(StyleSheetIdConstants.FIRST_ID as StyleSheetId)
+}
+
+export interface ItemIds<ItemType, ItemId extends number> {
+  clear(this: void): void
+  get(this: void, item: ItemType): ItemId | undefined
+  getOrInsert(this: void, item: ItemType): ItemId
+  get size(): number
+}
+
+function createIdMap<ItemType, ItemId extends number>(firstId: ItemId): ItemIds<ItemType, ItemId> {
+  return createItemIds(() => new Map<ItemType, ItemId>(), firstId)
+}
+
+function createWeakIdMap<ItemType extends object, ItemId extends number>(firstId: ItemId): ItemIds<ItemType, ItemId> {
+  return createItemIds(() => new WeakMap<ItemType, ItemId>(), firstId)
+}
+
+interface MapLike<Key, Value> {
+  get(key: Key): Value | undefined
+  set(key: Key, value: Value): void
+}
+
+function createItemIds<ItemType, ItemId extends number>(
+  createMap: () => MapLike<ItemType, ItemId>,
+  firstId: ItemId
+): ItemIds<ItemType, ItemId> {
+  let map = createMap()
+  let nextId = firstId
+
+  const get = (object: ItemType): ItemId | undefined => map.get(object)
+
+  return {
+    clear(): void {
+      map = createMap()
+      nextId = firstId
+    },
+    get,
+    getOrInsert(object: ItemType): ItemId {
+      // Try to reuse any existing id.
+      let id = get(object)
+      if (id === undefined) {
+        id = nextId++ as ItemId
+        map.set(object, id)
+      }
+      return id
+    },
+    get size(): number {
+      return nextId - firstId
+    },
+  }
+}