Bug: lib not working for node12 if not bundled with tools like esbuild

[flochaz]

Bug description

Node12 with standard bundling of lambda does not work and throw Runtime.UserCodeSyntaxError: SyntaxError: Unexpected token '.'

Expected Behavior

Installing and bundling my lambda with powertools "normally" should work on node12 runtime.

Current Behavior

Given a function bundled as a zip including @aws-lambda-powertools/* modules in node_modules and importing the lib in the index.js such as:

const { Logger } = require('@aws-lambda-powertools/logger');
const { Metrics } = require('@aws-lambda-powertools/metrics');
const { Tracer } = require('@aws-lambda-powertools/tracer');

When triggered, it will throw the following exception if runtime is Node12.x:

{"errorType":"Runtime.UserCodeSyntaxError","errorMessage":"SyntaxError: Unexpected token '.'","stack":["Runtime.UserCodeSyntaxError: SyntaxError: Unexpected token '.'"," at _loadUserApp (/var/runtime/UserFunction.js:98:13)"," at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)"," at Object.<anonymous> (/var/runtime/index.js:43:30)"," at Module._compile (internal/modules/cjs/loader.js:999:30)"," at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)"," at Module.load (internal/modules/cjs/loader.js:863:32)"," at Function.Module._load (internal/modules/cjs/loader.js:708:14)"," at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)"," at internal/main/run_main_module.js:17:47"]}

Possible Solution

1. Update the doc to mention that
   1. lambda should be bundled with tools like esbuild
   2. lambda layer won't work for node12
2. Fix the bundling of the lib to work with node12

Steps to Reproduce

Check https://github.com/awslabs/aws-lambda-powertools-typescript/runs/6521588868?check_suite_focus=true

or

An easyway to reproduce is to test the lambda layer

git clone https://github.com/awslabs/aws-lambda-powertools-typescript.git
cd layer-publisher
npm ci
RUNTIME=node12.x npm run test:e2e

You will get the following failure

    console.log
      [{"logs":["START RequestId: 334e421c-54ec-4fbe-b88b-f6db69398589 Version: $LATEST","2022-05-20T09:51:44.303Z\tundefined\tERROR\tUncaught Exception \t{\"errorType\":\"Runtime.UserCodeSyntaxError\",\"errorMessage\":\"SyntaxError: Unexpected token '.'\",\"stack\":[\"Runtime.UserCodeSyntaxError: SyntaxError: Unexpected token '.'\",\"    at _loadUserApp (/var/runtime/UserFunction.js:98:13)\",\"    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)\",\"    at Object.<anonymous> (/var/runtime/index.js:43:30)\",\"    at Module._compile (internal/modules/cjs/loader.js:999:30)\",\"    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)\",\"    at Module.load (internal/modules/cjs/loader.js:863:32)\",\"    at Function.Module._load (internal/modules/cjs/loader.js:708:14)\",\"    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)\",\"    at internal/main/run_main_module.js:17:47\"]}","2022-05-20T09:51:45.903Z\tundefined\tERROR\tUncaught Exception \t{\"errorType\":\"Runtime.UserCodeSyntaxError\",\"errorMessage\":\"SyntaxError: Unexpected token '.'\",\"stack\":[\"Runtime.UserCodeSyntaxError: SyntaxError: Unexpected token '.'\",\"    at _loadUserApp (/var/runtime/UserFunction.js:98:13)\",\"    at Object.module.exports.load (/var/runtime/UserFunction.js:140:17)\",\"    at Object.<anonymous> (/var/runtime/index.js:43:30)\",\"    at Module._compile (internal/modules/cjs/loader.js:999:30)\",\"    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)\",\"    at Module.load (internal/modules/cjs/loader.js:863:32)\",\"    at Function.Module._load (internal/modules/cjs/loader.js:708:14)\",\"    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)\",\"    at internal/main/run_main_module.js:17:47\"]}","END RequestId: 334e421c-54ec-4fbe-b88b-f6db69398589","REPORT RequestId: 334e421c-54ec-4fbe-b88b-f6db69398589\tDuration: 1771.15 ms\tBilled Duration: 1772 ms\tMemory Size: 128 MB\tMax Memory Used: 13 MB\t","Unknown application error occurred","Runtime.UserCodeSyntaxError"]}]

      at Object.<anonymous> (tests/e2e/happy-case.test.ts:74:13)
          at runMicrotasks (<anonymous>)

  ● Without layer package is usable with nodejs12.x runtime lambda

Environment

• Powertools version used: 0.9.-
• Packaging format (Layers, npm): Layer or npm
• AWS Lambda function runtime: Node12
• Debugging logs: see above

Related issues, RFCs

detected while testing layer: #884

[dreamorosi]

In our current tsconfig.json we are using ES2020 as target (example here) but according to the TS documentation (link) the mapping for node12.x should be ES2019:

{
  "compilerOptions": {
    "lib": ["ES2019"],
    "module": "commonjs",
    "target": "ES2019"
  }
}

Maybe this is the issue?

But then I don't fully understand why the integration tests we are running don't break.

[saragerion]

Example of compiler options for Node 12

[ijemmy]

Note on this. Target2019 doesn't support ?. argument. So code like this:

//in target 2020
subsegment?.close();

will be:

//in target 2019
subsegment === null || subsegment === void 0 ? void 0 : subsegment.close();

This is fine functionally. But it reduces our unit test branch coverage and breaks our commit/push hooks.

The options to fix this are:

1. use as to cast to a type that is not optional
2. use ! to tell typescript that there is always a value (but we'll need to ignore with // eslint-disable-next-line @typescript-eslint/no-non-null-assertion)
3. Add test case where it makes sense.

?. is used in many places. I'll be using different options based on situation.

Ref: https://linguinecode.com/post/how-to-solve-typescript-possibly-undefined-value

[github-actions]

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