Bug: `sam build` continues even if Typsecript compilation fails

Description:

After adding an intentional TS error (e.g. renamed a variable without refactoring), and running sam build, I’m told “Build Succeeded”. Running tsc directly shows the error correctly.

My directory structure is as follows:

<root>
 |--> app
 |     |--> node_modules
 |     |--> src
 |     |     |--> app.ts    # and other TS files
 |     |--> package.json    # and other config files
 |     |--> tsconfig.json
 |--> node_modules          # for building e.g. rimraf
 |--> package.json          #   ^^
 |--> samconfig.toml
 |--> template.yaml

I run sam build from the root dir. In template.yml I have this (partial example):

  Function:
    Type: AWS::Serverless::Function
    # ...
    Metadata:
      BuildMethod: esbuild
      BuildProperties:
        Minify: false
        Target: es2020
        Sourcemap: true
        EntryPoints:
          - src/app.ts

To work around this, I have a wrapper shell script in which I call the build function to run tsc before sam build (partial example):

#!/bin/bash
set -e

function build() {
    clean
    (cd app; npx tsc) # `sam build` seems to continue even if TSC fails ... ?
    sam build "$@"
    validate
}

"$@"

So I start the build via ./scripts.sh build.

Steps to reproduce:

Create a simple Typescript / SAM project. Add a line of code which causes tsc to fail. Run sam build and observe that it does not indicate failure.

Observed result:

sam build does not report tsc errors / does not abort the build process on such errors.

Expected result:

sam build should abort the process if tsc fails.

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: Manjaro Linux
2. sam --version: 1.55.0
3. AWS region: N/A

[jfuss]

@JoshMcCullough As far as I can tell from the code, we are: https://github.com/aws/aws-lambda-builders/blob/develop/aws_lambda_builders/workflows/nodejs_npm_esbuild/esbuild.py#L98

[lucashuy]

Thanks for raising this issue to us. To sum up, aws-lambda-builders (the library that sam build) uses esbuild to transpile Typescript back to Javascript instead of using tsc. Some things that will cause tsc to fail might not fail for esbuild, hence your observed result. Feel free to (re)open an issue for anything you might find!