chore: remove unused promisify code (#21114)

docs/api/modernization/promisification.md

@@ -1,17 +1,6 @@
 ## Promisification
 
-The Electron team is currently undergoing an initiative to convert callback-based functions in Electron to return Promises. During this transition period, both the callback and Promise-based versions of these functions will work correctly, and will both be documented.
+The Electron team recently underwent an initiative to convert callback-based APIs to Promise-based ones. See converted functions below:
-
-To enable deprecation warnings for these updated functions, use the [`process.enablePromiseAPIs` runtime flag](../process.md#processenablepromiseapis).
-
-When a majority of affected functions are migrated, this flag will be enabled by default and all developers will be able to see these deprecation warnings. At that time, the callback-based versions will also be removed from documentation. This document will be continuously updated as more functions are converted.
-
-### Candidate Functions
-
-- [app.importCertificate(options, callback)](https://github.com/electron/electron/blob/master/docs/api/app.md#importCertificate)
-- [contents.print([options], [callback])](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#print)
-
-### Converted Functions
 
 - [app.getFileIcon(path[, options], callback)](https://github.com/electron/electron/blob/master/docs/api/app.md#getFileIcon)
 - [contents.capturePage([rect, ]callback)](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#capturePage)

docs/api/process.md

@@ -82,12 +82,6 @@ A `Boolean` that controls whether or not deprecation warnings are printed to `st
 Setting this to `true` will silence deprecation warnings. This property is used
 instead of the `--no-deprecation` command line flag.
 
-### `process.enablePromiseAPIs`
-
-A `Boolean` that controls whether or not deprecation warnings are printed to `stderr` when
-formerly callback-based APIs converted to Promises are invoked using callbacks. Setting this to `true`
-will enable deprecation warnings.
-
 ### `process.resourcesPath` _Readonly_
 
 A `String` representing the path to the resources directory.

lib/common/api/deprecate.ts

@@ -116,64 +116,6 @@ const deprecate: ElectronInternal.DeprecationUtil = {
     })
   },
 
-  // deprecate a callback-based function in favor of one returning a Promise
-  promisify: <T extends (...args: any[]) => any>(fn: T): T => {
-    const fnName = fn.name || 'function'
-    const oldName = `${fnName} with callbacks`
-    const newName = `${fnName} with Promises`
-    const warn = warnOnce(oldName, newName)
-
-    return function (this: any, ...params: any[]) {
-      let cb: Function | undefined
-      if (params.length > 0 && typeof params[params.length - 1] === 'function') {
-        cb = params.pop()
-      }
-      const promise = fn.apply(this, params)
-      if (!cb) return promise
-      if (process.enablePromiseAPIs) warn()
-      return promise
-        .then((res: any) => {
-          process.nextTick(() => {
-            cb!.length === 2 ? cb!(null, res) : cb!(res)
-          })
-          return res
-        }, (err: Error) => {
-          process.nextTick(() => {
-            cb!.length === 2 ? cb!(err) : cb!()
-          })
-          throw err
-        })
-    } as T
-  },
-
-  // convertPromiseValue: Temporarily disabled until it's used
-  // deprecate a callback-based function in favor of one returning a Promise
-  promisifyMultiArg: <T extends (...args: any[]) => any>(fn: T /* convertPromiseValue: (v: any) => any */): T => {
-    const fnName = fn.name || 'function'
-    const oldName = `${fnName} with callbacks`
-    const newName = `${fnName} with Promises`
-    const warn = warnOnce(oldName, newName)
-
-    return function (this: any, ...params) {
-      let cb: Function | undefined
-      if (params.length > 0 && typeof params[params.length - 1] === 'function') {
-        cb = params.pop()
-      }
-      const promise = fn.apply(this, params)
-      if (!cb) return promise
-      if (process.enablePromiseAPIs) warn()
-      return promise
-        .then((res: any) => {
-          process.nextTick(() => {
-            // eslint-disable-next-line standard/no-callback-literal
-            cb!.length > 2 ? cb!(null, ...res) : cb!(...res)
-          })
-        }, (err: Error) => {
-          process.nextTick(() => cb!(err))
-        })
-    } as T
-  },
-
   // change the name of a property
   renameProperty: (o, oldName, newName) => {
     const warn = warnOnce(oldName, newName)

spec-main/api-deprecate-spec.ts

@@ -192,79 +192,4 @@ describe('deprecate', () => {
       expect(warnings[0]).to.equal('\'old\' is deprecated and will be removed. Please use \'new\' instead.')
     })
   })
-
-  describe('promisify', () => {
-    const expected = 'Hello, world!'
-    let promiseFunc: (param: any) => Promise<any>
-    let warnings: string[]
-
-    const enableCallbackWarnings = () => {
-      warnings = []
-      deprecate.setHandler(warning => warnings.push(warning))
-      process.enablePromiseAPIs = true
-    }
-
-    beforeEach(() => {
-      deprecate.setHandler(null)
-      process.throwDeprecation = true
-
-      promiseFunc = param => new Promise((resolve) => resolve(param))
-    })
-
-    it('acts as a pass-through for promise-based invocations', async () => {
-      enableCallbackWarnings()
-      promiseFunc = deprecate.promisify(promiseFunc)
-
-      const actual = await promiseFunc(expected)
-      expect(actual).to.equal(expected)
-      expect(warnings).to.have.lengthOf(0)
-    })
-
-    it('only calls back an error if the callback is called with (err, data)', async () => {
-      enableCallbackWarnings()
-      const erringPromiseFunc = deprecate.promisify(
-        () => new Promise((resolve, reject) => {
-          reject(new Error('fail'))
-        })
-      )
-
-      {
-        const [err, data] = await new Promise(resolve => {
-          (erringPromiseFunc as any)((err: Error | undefined, data: any) => {
-            resolve([err, data])
-          }).catch(() => { /* silence deprecation warning */ })
-        })
-        expect(data).to.be.undefined()
-        expect(err).to.be.an.instanceOf(Error).with.property('message', 'fail')
-      }
-      {
-        const data = await new Promise(resolve => {
-          (erringPromiseFunc as any)((data: any) => { resolve(data) })
-            .catch(() => { /* silence deprecation warning */ })
-        })
-        expect(data).to.be.undefined()
-      }
-    })
-
-    it('warns exactly once for callback-based invocations', (done) => {
-      enableCallbackWarnings()
-      promiseFunc = deprecate.promisify(promiseFunc)
-
-      let callbackCount = 0
-      const invocationCount = 3
-      const callback = (actual: number) => {
-        expect(actual).to.equal(expected)
-        expect(warnings).to.have.lengthOf(1)
-        expect(warnings[0]).to.include('promiseFunc')
-        callbackCount += 1
-        if (callbackCount === invocationCount) {
-          done()
-        }
-      }
-
-      for (let i = 0; i < invocationCount; i += 1) {
-        (promiseFunc as any)(expected, callback)
-      }
-    })
-  })
 })

typings/internal-electron.d.ts

@@ -90,11 +90,6 @@ declare namespace ElectronInternal {
     removeProperty<T, K extends (keyof T & string)>(object: T, propertyName: K): T;
     renameProperty<T, K extends (keyof T & string)>(object: T, oldName: string, newName: K): T;
     moveAPI(fn: Function, oldUsage: string, newUsage: string): Function;
-
-    promisify<T extends (...args: any[]) => any>(fn: T): T;
-
-    // convertPromiseValue: Temporarily disabled until it's used
-    promisifyMultiArg<T extends (...args: any[]) => any>(fn: T, /*convertPromiseValue: (v: any) => any*/): T;
   }
 
   interface DesktopCapturer {