Refactor models to use bundleAsync and lock regions (#171)

__tests__/lib/async/bundle.test.ts

@@ -0,0 +1,47 @@
+import {bundleAsync} from '../../../src/lib/async/bundle'
+
+describe('bundle', () => {
+  it('bundles multiple simultaneous calls into one execution', async () => {
+    let calls = 0
+    const fn = bundleAsync(async () => {
+      calls++
+      await new Promise(r => setTimeout(r, 1))
+      return 'hello'
+    })
+    const [res1, res2, res3] = await Promise.all([fn(), fn(), fn()])
+    expect(calls).toEqual(1)
+    expect(res1).toEqual('hello')
+    expect(res2).toEqual('hello')
+    expect(res3).toEqual('hello')
+  })
+  it('does not bundle non-simultaneous calls', async () => {
+    let calls = 0
+    const fn = bundleAsync(async () => {
+      calls++
+      await new Promise(r => setTimeout(r, 1))
+      return 'hello'
+    })
+    const res1 = await fn()
+    const res2 = await fn()
+    const res3 = await fn()
+    expect(calls).toEqual(3)
+    expect(res1).toEqual('hello')
+    expect(res2).toEqual('hello')
+    expect(res3).toEqual('hello')
+  })
+  it('is not affected by rejections', async () => {
+    let calls = 0
+    const fn = bundleAsync(async () => {
+      calls++
+      await new Promise(r => setTimeout(r, 1))
+      throw new Error()
+    })
+    const res1 = await fn().catch(() => 'reject')
+    const res2 = await fn().catch(() => 'reject')
+    const res3 = await fn().catch(() => 'reject')
+    expect(calls).toEqual(3)
+    expect(res1).toEqual('reject')
+    expect(res2).toEqual('reject')
+    expect(res3).toEqual('reject')
+  })
+})