Some refactoring (#562)

* refactor: remove unnecessary 'else'

* refactor: change _buildAndArchive function to async-await

Author: abetomo

lib/main.js

@@ -530,28 +530,27 @@ Emulate only the body of the API Gateway event.
           resolve()
         })
       })
-    } else {
-      return new Promise((resolve, reject) => {
-        fs.readdir(codeDirectory, (err, files) => {
-          if (err) return reject(err)
+    }
+    return new Promise((resolve, reject) => {
+      fs.readdir(codeDirectory, (err, files) => {
+        if (err) return reject(err)
 
-          Promise.all(files.map(file => {
-            return new Promise((resolve, reject) => {
-              if (keepNodeModules && file === 'node_modules') {
+        Promise.all(files.map(file => {
+          return new Promise((resolve, reject) => {
+            if (keepNodeModules && file === 'node_modules') {
+              resolve()
+            } else {
+              fs.remove(path.join(codeDirectory, file), err => {
+                if (err) return reject(err)
                 resolve()
-              } else {
-                fs.remove(path.join(codeDirectory, file), err => {
-                  if (err) return reject(err)
-                  resolve()
-                })
-              }
-            })
-          })).then(() => {
-            resolve()
+              })
+            }
           })
+        })).then(() => {
+          resolve()
         })
       })
-    }
+    })
   }
 
   _setRunTimeEnvironmentVars (program) {
@@ -664,7 +663,7 @@ Emulate only the body of the API Gateway event.
     })
   }
 
-  _buildAndArchive (program) {
+  async _buildAndArchive (program) {
     if (!fs.existsSync('.env')) {
       console.warn('[Warning] `.env` file does not exist.')
       console.info('Execute `node-lambda setup` as necessary and set it up.')
@@ -683,24 +682,16 @@ they may not work as expected in the Lambda environment.
     const codeDirectory = this._codeDirectory()
     const lambdaSrcDirectory = program.sourceDirectory ? program.sourceDirectory.replace(/\/$/, '') : '.'
 
-    return Promise.resolve().then(() => {
-      return this._cleanDirectory(codeDirectory, program.keepNodeModules)
-    }).then(() => {
-      console.log('=> Moving files to temporary directory')
-      return this._fileCopy(program, lambdaSrcDirectory, codeDirectory, true)
-    }).then(() => {
-      if (program.keepNodeModules) {
-        return Promise.resolve()
-      } else {
-        console.log(`=> Running npm ${this._shouldUseNpmCi(codeDirectory) ? 'ci' : 'install'} --production`)
-        return this._npmInstall(program, codeDirectory)
-      }
-    }).then(() => {
-      return this._postInstallScript(program, codeDirectory)
-    }).then(() => {
-      console.log('=> Zipping deployment package')
-      return this._zip(program, codeDirectory)
-    })
+    await this._cleanDirectory(codeDirectory, program.keepNodeModules)
+    console.log('=> Moving files to temporary directory')
+    await this._fileCopy(program, lambdaSrcDirectory, codeDirectory, true)
+    if (!program.keepNodeModules) {
+      console.log(`=> Running npm ${this._shouldUseNpmCi(codeDirectory) ? 'ci' : 'install'} --production`)
+      await this._npmInstall(program, codeDirectory)
+    }
+    await this._postInstallScript(program, codeDirectory)
+    console.log('=> Zipping deployment package')
+    return this._zip(program, codeDirectory)
   }
 
   _listEventSourceMappings (lambda, params) {