fix: add .finally method

fix #120

README.md

@@ -14,7 +14,7 @@ but more thorough, because that package doesn't seem very actively maintained.
 `promisify-child-process` provides a **drop-in replacement** for the
 original `child_process` functions, not just duplicate methods that
 return a `Promise`. So when you call `exec(...)` we still return a
-`ChildProcess` instance, just with `.then()` and `.catch()` added to
+`ChildProcess` instance, just with `.then()`, `.catch()`, and `.finally()` added to
 make it promise-friendly.
 
 ## Install and Set-up

package.json

@@ -134,7 +134,8 @@
     "prettier-eslint": "^8.8.2",
     "rimraf": "^2.6.0",
     "semantic-release": "^15.13.31",
-    "typescript": "^3.7.3"
+    "typescript": "^3.7.3",
+    "waait": "^1.0.5"
   },
   "dependencies": {},
   "renovate": {

src/index.js

@@ -26,6 +26,21 @@ type PromisifyChildProcessBaseOpts = {
 export type SpawnOpts = child_process$spawnOpts & PromisifyChildProcessBaseOpts
 export type ForkOpts = child_process$forkOpts & PromisifyChildProcessBaseOpts
 
+const bindFinally = <T>(promise: Promise<T>) => (
+  handler: () => mixed
+): Promise<T> =>
+  // don't assume we're running in an environment with Promise.finally
+  promise.then(
+    async (value: any): any => {
+      await handler()
+      return value
+    },
+    async (reason: any): any => {
+      await handler()
+      throw reason
+    }
+  )
+
 function joinChunks(
   chunks: $ReadOnlyArray<string | Buffer>,
   encoding: ?string
@@ -139,6 +154,9 @@ export function promisifyChildProcess(
   return (Object.create(child, {
     then: { value: _promise.then.bind(_promise) },
     catch: { value: _promise.catch.bind(_promise) },
+    finally: {
+      value: bindFinally(_promise),
+    },
   }): any)
 }
 
@@ -196,6 +214,7 @@ function promisifyExecMethod(method: any): any {
     return (Object.create((child: any), {
       then: { value: _promise.then.bind(_promise) },
       catch: { value: _promise.catch.bind(_promise) },
+      finally: { value: bindFinally(_promise) },
     }): any)
   }
 }

test/index.js

@@ -5,6 +5,7 @@ import { describe, it, before, after } from 'mocha'
 import { expect } from 'chai'
 import path from 'path'
 import fs from 'fs-extra'
+import delay from 'waait'
 
 before(() =>
   Promise.all([
@@ -50,11 +51,16 @@ describe('spawn', function() {
   this.timeout(30000)
 
   it('resolves with process output', async () => {
+    let finallyDone = false
     const { stdout, stderr } = await spawn(
       process.execPath,
       [require.resolve('./resolvesWithProcessOutput')],
       { maxBuffer: 200 * 1024 }
-    )
+    ).finally(async () => {
+      await delay(50)
+      finallyDone = true
+    })
+    expect(finallyDone, 'finally handler finished').to.be.true
     if (stdout == null || stderr == null) throw new Error('missing output')
     if (!(stdout instanceof Buffer))
       throw new Error('expected stdout to be a buffer')
@@ -94,10 +100,17 @@ describe('spawn', function() {
     expect(stderr).to.equal('world')
   })
   it('rejects with exit code', async () => {
+    let finallyDone = false
     let error
     await spawn(process.execPath, [require.resolve('./rejectsWithExitCode')], {
       maxBuffer: 200 * 1024,
-    }).catch(err => (error = err))
+    })
+      .finally(async () => {
+        await delay(50)
+        finallyDone = true
+      })
+      .catch(err => (error = err))
+    expect(finallyDone, 'finally handler finished').to.be.true
     if (error == null) throw new Error('missing error')
     const { code, message, stdout, stderr } = error
     expect(message).to.equal('Process exited with code 2')
@@ -157,10 +170,15 @@ describe('fork', function() {
   this.timeout(30000)
 
   it('resolves with process output', async () => {
+    let finallyDone = false
     const { stdout, stderr } = await fork(
       require.resolve('./resolvesWithProcessOutput'),
       { silent: true, maxBuffer: 200 * 1024 }
-    )
+    ).finally(async () => {
+      await delay(50)
+      finallyDone = true
+    })
+    expect(finallyDone, 'finally handler finished').to.be.true
     if (stdout == null || stderr == null) throw new Error('missing output')
     if (!(stdout instanceof Buffer))
       throw new Error('expected stdout to be a buffer')
@@ -198,11 +216,18 @@ describe('fork', function() {
     expect(stderr).to.equal('world')
   })
   it('rejects with exit code', async () => {
+    let finallyDone = false
     let error
     await fork(require.resolve('./rejectsWithExitCode'), {
       silent: true,
       maxBuffer: 200 * 1024,
-    }).catch(err => (error = err))
+    })
+      .finally(async () => {
+        await delay(50)
+        finallyDone = true
+      })
+      .catch(err => (error = err))
+    expect(finallyDone, 'finally handler finished').to.be.true
     if (error == null) throw new Error('missing error')
     const { code, message, stdout, stderr } = error
     expect(message).to.equal('Process exited with code 2')

yarn.lock

@@ -8313,6 +8313,11 @@ vue-eslint-parser@^2.0.2:
     esquery "^1.0.0"
     lodash "^4.17.4"
 
+waait@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/waait/-/waait-1.0.5.tgz#6a3c7aaa88bd0a1a545e9d47890b9595bebf9aa7"
+  integrity sha512-wp+unA4CpqxvBUKHHv8D86fK4jWByHAWyhEXXVHfVUZfK+16ylpj7hjQ58Z8j9ntu8XNukRQT8Fi5qbyJ8rkyw==
+
 wcwidth@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/wcwidth/-/wcwidth-1.0.1.tgz#f0b0dcf915bc5ff1528afadb2c0e17b532da2fe8"