feat: add generator detection functions to utils (#2923)

Functions like this are used in several places in the stack so
move them to the utils package for reuse.

Incorporates changes from #2918

packages/utils/package.json

@@ -84,6 +84,14 @@
       "types": "./dist/src/ip-port-to-multiaddr.d.ts",
       "import": "./dist/src/ip-port-to-multiaddr.js"
     },
+    "./is-async-generator": {
+      "types": "./dist/src/is-async-generator.d.ts",
+      "import": "./dist/src/is-async-generator.js"
+    },
+    "./is-generator": {
+      "types": "./dist/src/is-generator.d.ts",
+      "import": "./dist/src/is-generator.js"
+    },
     "./is-promise": {
       "types": "./dist/src/is-promise.d.ts",
       "import": "./dist/src/is-promise.js"

packages/utils/src/is-async-generator.ts

@@ -0,0 +1,10 @@
+export function isAsyncGenerator (obj: unknown): obj is AsyncGenerator {
+  if (obj == null) return false
+  const asyncIterator = (obj as { [Symbol.asyncIterator]?: unknown })?.[
+    Symbol.asyncIterator
+  ]
+  if (typeof asyncIterator !== 'function') return false
+
+  const instance = obj as { next?: unknown }
+  return typeof instance.next === 'function'
+}

packages/utils/src/is-generator.ts

@@ -0,0 +1,8 @@
+export function isGenerator (obj: unknown): obj is Generator {
+  if (obj == null) return false
+  const iterator = (obj as { [Symbol.iterator]?: unknown })?.[Symbol.iterator]
+  if (typeof iterator !== 'function') return false
+
+  const instance = obj as { next?: unknown }
+  return typeof instance.next === 'function'
+}

packages/utils/test/is-async-generator.spec.ts

@@ -0,0 +1,41 @@
+import { expect } from 'aegir/chai'
+import { isAsyncGenerator } from '../src/is-async-generator.js'
+
+describe('is-async-generator', () => {
+  it('should return true if the value is an async generator', () => {
+    async function * asyncGen (): AsyncGenerator<number> {
+      yield 1
+    }
+    const asyncGenerator = asyncGen()
+    expect(isAsyncGenerator(asyncGenerator)).to.be.true()
+
+    const asyncGenObj = (async function * () {
+      yield 1
+    })()
+    expect(isAsyncGenerator(asyncGenObj)).to.be.true()
+  })
+
+  it('should return false if the value is not an async generator', () => {
+    expect(isAsyncGenerator(1)).to.be.false()
+    expect(isAsyncGenerator('string')).to.be.false()
+    expect(isAsyncGenerator({})).to.be.false()
+    expect(isAsyncGenerator([])).to.be.false()
+    expect(isAsyncGenerator(null)).to.be.false()
+    expect(isAsyncGenerator(undefined)).to.be.false()
+    expect(isAsyncGenerator(() => {})).to.be.false()
+    expect(isAsyncGenerator(async () => {})).to.be.false()
+    expect(
+      isAsyncGenerator(function * () {
+        yield 1
+      })
+    ).to.be.false()
+    expect(
+      isAsyncGenerator(async function * () {
+        yield 1
+      })
+    ).to.be.false() // async generator function, not generator
+    expect(isAsyncGenerator(Promise.resolve())).to.be.false()
+    expect(isAsyncGenerator({ next: async () => {} })).to.be.false()
+    expect(isAsyncGenerator({ [Symbol.asyncIterator]: () => {} })).to.be.false()
+  })
+})

packages/utils/test/is-generator.spec.ts

@@ -0,0 +1,41 @@
+import { expect } from 'aegir/chai'
+import { isGenerator } from '../src/is-generator.js'
+
+describe('is-generator', () => {
+  it('should return true if the value is a generator', () => {
+    function * gen (): Generator<number> {
+      yield 1
+    }
+    const generator = gen()
+    expect(isGenerator(generator)).to.be.true()
+
+    const genObj = (function * () {
+      yield 1
+    })()
+    expect(isGenerator(genObj)).to.be.true()
+  })
+
+  it('should return false if the value is not a generator', () => {
+    expect(isGenerator(1)).to.be.false()
+    expect(isGenerator('string')).to.be.false()
+    expect(isGenerator({})).to.be.false()
+    expect(isGenerator([])).to.be.false()
+    expect(isGenerator(null)).to.be.false()
+    expect(isGenerator(undefined)).to.be.false()
+    expect(isGenerator(() => {})).to.be.false()
+    expect(isGenerator(async () => {})).to.be.false()
+    expect(
+      isGenerator(function * () {
+        yield 1
+      })
+    ).to.be.false() // generator function, not generator
+    expect(
+      isGenerator(async function * () {
+        yield 1
+      })
+    ).to.be.false()
+    expect(isGenerator(Promise.resolve())).to.be.false()
+    expect(isGenerator({ next: () => {} })).to.be.false()
+    expect(isGenerator({ [Symbol.iterator]: () => {} })).to.be.false()
+  })
+})

packages/utils/test/is-promise.spec.ts

@@ -31,4 +31,32 @@ describe('is-promise', () => {
   it('should not detect partial promise', () => {
     expect(isPromise({ then: true })).to.be.false()
   })
+
+  it('should return true if the value is a promise', () => {
+    expect(isPromise(Promise.resolve())).to.be.true()
+    expect(isPromise(new Promise(() => {}))).to.be.true()
+    expect(isPromise(Promise.reject(new Error('test')))).to.be.true()
+  })
+
+  it('should return false if the value is not a promise', () => {
+    expect(isPromise(1)).to.be.false()
+    expect(isPromise('string')).to.be.false()
+    expect(isPromise({})).to.be.false()
+    expect(isPromise([])).to.be.false()
+    expect(isPromise(null)).to.be.false()
+    expect(isPromise(undefined)).to.be.false()
+    expect(isPromise(() => {})).to.be.false()
+    expect(isPromise(async () => {})).to.be.false()
+    expect(
+      isPromise(function * () {
+        yield 1
+      })
+    ).to.be.false()
+    expect(
+      isPromise(async function * () {
+        yield 1
+      })
+    ).to.be.false()
+    expect(isPromise({ then: 1 })).to.be.false()
+  })
 })

packages/utils/typedoc.json

@@ -11,6 +11,8 @@
     "./src/filters/index.ts",
     "./src/global-unicast-ip.ts",
     "./src/ip-port-to-multiaddr.ts",
+    "./src/is-async-generator.ts",
+    "./src/is-generator.ts",
     "./src/is-promise.ts",
     "./src/link-local-ip.ts",
     "./src/moving-average.ts",