Unable to import "function handler" in logs

[tzookb]

This is a Bug Report

Description

Im using serverless-webpack with serverless-http with express. I have my serverless.yaml:

custom:
  webpack:
    packager: 'yarn'
    webpackConfig: './webpack.config.js'

functions:
  app:
    handler: main.handler
    ....

this is my main.js file:

const serverless = require('serverless-http');
const app = require('./app');
module.exports.handler = serverless(app);

and the app file is the express app.

When Im using serverless offline start it works well with webpack build. But when deploying I see the cant find "main" in the trace...

Any help is appreciated!

For bug reports:

• What went wrong? webpack builds properly with serverless local, but when deploying I get "main" not found. (this is my function handler)

• What did you expect should have happened? deploy will go well and app will be useable

• What was the config you used?

• What stacktrace or error message from your provider did you see?

Unable to import module 'main': Error
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (/var/task/main.js:1:3496)
at n (/var/task/main.js:1:220)
at Object.<anonymous> (/var/task/main.js:1:3559)
at n (/var/task/main.js:1:220)
at /var/task/main.js:1:1019
at Object.<anonymous> (/var/task/main.js:1:1029)

Similar or dependent issue(s): *

Additional Data

• Serverless-Webpack Version you're using: 5.1.5
• Webpack version you're using: 4.12.0
• Serverless Framework Version you're using: 1.32.0
• Operating System: mac
• Stack Trace (if available):

Unable to import module 'main': Error
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (/var/task/main.js:1:3496)
at n (/var/task/main.js:1:220)
at Object.<anonymous> (/var/task/main.js:1:3559)
at n (/var/task/main.js:1:220)
at /var/task/main.js:1:1019
at Object.<anonymous> (/var/task/main.js:1:1029)

[asplogic]

Not sure if it's same problem but I encountered a similar issue that I spent countless hours debugging. What version of node are you using locally? I updated from v8.10 to v8.12.0 and then the issues went away. I know you are suppose to use the same version with aws lambda but I couldn't get past this issue any other way. Hopefully it works for you.

[AdamZaczek]

I have the exact same issue Deps

{
  "devDependencies": {
    "@babel/plugin-transform-runtime": "^7.2.0",
    "@babel/preset-env": "^7.2.3",
    "@babel/register": "^7.0.0",
    "@babel/runtime": "^7.2.0",
    "axios": "^0.18.0",
    "babel-cli": "^6.26.0",
    "babel-loader": "^8.0.4",
    "babel-preset-env": "^1.7.0",
    "babel-preset-stage-2": "^6.24.1",
    "chai": "^4.1.2",
    "graphql-playground-middleware-express": "^1.7.8",
    "mocha": "^5.2.0",
    "morgan": "^1.9.1",
    "serverless-offline": "^3.31.3",
    "webpack": "^4.28.2",
    "webpack-node-externals": "^1.7.2"
  },
  "dependencies": {
    "apollo-server": "^2.3.1",
    "apollo-server-express": "^2.3.1",
    "apollo-server-lambda": "^2.3.1",
    "bcryptjs": "^2.4.3",
    "cors": "^2.8.4",
    "dataloader": "^1.4.0",
    "dotenv": "^6.2.0",
    "express": "^4.16.4",
    "graphql": "^14.0.2",
    "graphql-resolvers": "^0.2.2",
    "jsonwebtoken": "^8.3.0",
    "mongoose": "^5.4.0",
    "serverless": "^1.35.1",
    "serverless-http": "^1.8.0",
    "serverless-webpack": "^5.2.0"
  }

Serverless.yml

service: abc
tenant: adamzaczek
app: abc
plugins:
  - serverless-webpack
  - serverless-offline
custom:
  webpack:
    includeModules:
      forceExclude:
        - graphql-playground-middleware-express
        - morgan
        - "@babel/runtime"
    webpackConfig: ./webpack.config.js

provider:
  name: aws
  runtime: nodejs8.12
  stage: dev
  credentials:
    accessKeyId: totallyMyRealAccessKey
    secretAccessKey: notASecretAnymore
  region: us-east-1
functions:
  graphql:
    handler: index.handler
    events:
      - http:
          path: graphql
          method: post
          cors: true
  playground:
    handler: index.handler
    events:
      - http:
          path: playground
          method: get

webpack.config.js

const path = require("path");
const slsw = require("serverless-webpack");
const nodeExternals = require("webpack-node-externals");
module.exports = {
  entry: slsw.lib.entries,
  target: "node",
  mode: slsw.lib.webpack.isLocal ? "development" : "production",
  optimization: {
    minimize: false
  },
  performance: {
    hints: false
  },
  devtool: "nosources-source-map",
  externals: [nodeExternals()],
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: [
          {
            loader: "babel-loader"
          }
        ]
      }
    ]
  },
  output: {
    libraryTarget: "commonjs2",
    path: path.join(__dirname, ".webpack"),
    filename: "[name].js",
    sourceMapFilename: "[file].map"
  }
};

OS: darwin Node Version: 8.12.0 Serverless Version: 1.35.1

Logs from cloudwatch

Unable to import module 'index': Error
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (/var/task/index.js:122:18)
at __webpack_require__ (/var/task/index.js:21:30)
at Module.<anonymous> (/var/task/index.js:220:21)
at __webpack_require__ (/var/task/index.js:21:30)
at /var/task/index.js:85:18
at Object.<anonymous> (/var/task/index.js:88:10)

Zip file looks ok, it has index.js, index.js.map, package.json and node_modules. I've been developing the app using sls offline and I never had any issues. Do you guys have any ideas what might be wrong?

[AdamZaczek]

I managed to fix the issue. For me it was .babelrc config file. I was missing node 8.10 target. This is my working .babelrc:

{
  "presets": [["@babel/preset-env", { "targets": { "node": "8.10" } }]],
  "plugins": ["@babel/plugin-transform-runtime"]
}