Bug Fixed: Missing this context in method calls

package.json

@@ -1,6 +1,6 @@
 {
   "name": "class-logger",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "Boilerplate-free decorator-based class logging",
   "keywords": [
     "decorator",

src/class-wrapper.service.spec.ts

@@ -54,7 +54,7 @@ describe(ClassWrapperService.name, () => {
   })
 
   describe('wrapFunction', () => {
-    const logsSuccess = async (fn: jest.Mock, fnRes: any) => {
+    const logsSuccess = async (fn: jest.Mock, fnRes: any, ctx?: any) => {
       const config = ConfigService.config
       const className = 'Test'
       const propertyName = 'test'
@@ -73,8 +73,14 @@ describe(ClassWrapperService.name, () => {
       const spyLogError = jest.spyOn(config, 'logError')
 
       const classWrapperService: any = new ClassWrapperService()
-      const fnWrapped = classWrapperService.wrapFunction(config, fn, className, propertyName, classInstance)
-      const fnWrappedRes = await fnWrapped(...argsTest)
+      const fnWrapped: (...args: any) => any = classWrapperService.wrapFunction(
+        config,
+        fn,
+        className,
+        propertyName,
+        classInstance,
+      )
+      const fnWrappedRes = await fnWrapped.apply(ctx, argsTest)
       expect(fnWrappedRes).toBe(fnRes)
       expect(fn).toBeCalledTimes(1)
       expect(fn).toBeCalledWith(...argsTest)
@@ -121,7 +127,13 @@ describe(ClassWrapperService.name, () => {
       const spyLogError = jest.spyOn(config, 'logError')
 
       const classWrapperService: any = new ClassWrapperService()
-      const fnWrapped = classWrapperService.wrapFunction(config, fn, className, propertyName, classInstance)
+      const fnWrapped: (...args: any[]) => any = classWrapperService.wrapFunction(
+        config,
+        fn,
+        className,
+        propertyName,
+        classInstance,
+      )
       const fnWrappedPromise = (async () => fnWrapped(...argsTest))()
       await expect(fnWrappedPromise).rejects.toThrow(error)
       expect(fn).toBeCalledTimes(1)
@@ -164,6 +176,16 @@ describe(ClassWrapperService.name, () => {
         })
         await logError(fn, error)
       })
+      test('preserves this context', async () => {
+        const fnRes = Symbol()
+        const ctx = {}
+        // tslint:disable-next-line only-arrow-functions
+        const fn = jest.fn(function(this: any) {
+          expect(this).toBe(ctx)
+          return fnRes
+        })
+        await logsSuccess(fn, fnRes, ctx)
+      })
     })
 
     describe('asynchronous target function', () => {
@@ -268,7 +290,7 @@ describe(ClassWrapperService.name, () => {
       })
       expect(spyWrapClassInstance).toBeCalledTimes(1)
     })
-    test("wraps class and  doesn't log its construction", () => {
+    test("wraps class and doesn't log its construction", () => {
       const config: IClassLoggerConfig = {
         include: {
           construct: false,

src/class-wrapper.service.ts

@@ -28,7 +28,7 @@ export class ClassWrapperService {
     const classWrapper = this
     // Use non-arrow function to allow dynamic context
     // tslint:disable-next-line only-arrow-functions
-    return function(...args: any[]) {
+    return function(this: any, ...args: any[]) {
       const messageStart = config.formatter.start({
         args,
         classInstance,
@@ -56,7 +56,7 @@ export class ClassWrapperService {
       }
 
       try {
-        const res = fn(...args)
+        const res = fn.apply(this, args)
         if (classWrapper.isPromise(res)) {
           res
             .then((result: any) => {

src/formatter.service.spec.ts

@@ -29,7 +29,7 @@ describe(ClassLoggerFormatterService.name, () => {
     prop3: valTestClassProp3,
   })
   const dataStart: IClassLoggerFormatterStartData = {
-    args: ['test', Symbol(), { test: '123' }],
+    args: ['test', Symbol(), { test: '123' }, undefined],
     classInstance: new TestClass(),
     className: 'ClassNameTest',
     include: {
@@ -93,7 +93,7 @@ describe(ClassLoggerFormatterService.name, () => {
     test('returns stringified args', () => {
       const argsStr = (classLoggerFormatterService as any).args(dataStart)
       expect(argsStr).toBe(
-        `. Args: [${dataStart.args[0]}, ${dataStart.args[1].toString()}, ${stringify(dataStart.args[2])}]`,
+        `. Args: [${dataStart.args[0]}, ${dataStart.args[1].toString()}, ${stringify(dataStart.args[2])}, undefined]`,
       )
     })
   })
@@ -115,6 +115,13 @@ describe(ClassLoggerFormatterService.name, () => {
       const resStr = (classLoggerFormatterService as any).result(dataEnd)
       expect(resStr).toBe(`. Res: ${dataEnd.result}`)
     })
+    test('returns undefined', () => {
+      const resStr = (classLoggerFormatterService as any).result({
+        ...dataEnd,
+        result: undefined,
+      })
+      expect(resStr).toBe(`. Res: undefined`)
+    })
     test('returns stringified object result', () => {
       const resultObj = {
         test: 42,

src/formatter.service.ts

@@ -30,6 +30,7 @@ export interface IClassLoggerIncludeConfig {
 
 export class ClassLoggerFormatterService implements IClassLoggerFormatter {
   protected readonly placeholderNotAvailable = 'N/A'
+  protected readonly placeholderUndefined = 'undefined'
 
   public start(data: IClassLoggerFormatterStartData) {
     let message = this.base(data)
@@ -92,14 +93,17 @@ export class ClassLoggerFormatterService implements IClassLoggerFormatter {
     return stringify(classInsanceFiltered)
   }
   protected valueToString(res: any): string {
+    if (res === undefined) {
+      return this.placeholderUndefined
+    }
     if (typeof res !== 'object') {
       return res.toString()
     }
     if (res instanceof Error) {
       res = this.errorFormat(res)
     }
     if (Array.isArray(res)) {
-      const arrayWithStringifiedElements = res.map(this.valueToString)
+      const arrayWithStringifiedElements = res.map(this.valueToString.bind(this))
       return `[${arrayWithStringifiedElements.join(', ')}]`
     }
     return stringify(res)