Source map sources relative to temporary output path

[badeball]

Hi, Evan

Thanks for a wonderful library!

I have a question / something regarding the sources property of outputted (inline) sourcemaps. Given I have two files,

// foo.mjs
export default function foo () {
  console.log("YOLO!");
}

.. and

// index.mjs
import foo from "./foo.mjs"

foo();

.. and I build like the following

esbuild.build({
  entryPoints: ["index.mjs"],
  bundle: true,
  sourcemap: "inline"
});

.. I get a nice sources property containing ["foo.mjs", "index.mjs"]. However, this is all outputted to stdout. I'm using esbuild in part with Cypress, a testing utility, and preprocessors of Cypress are provided a temporary file location in which they are expected to output bundles. Hence, we build like

esbuild.build({
  entryPoints: ["index.mjs"],
  bundle: true,
  sourcemap: "inline",
  outfile: "/tmp/tmp-1153466-5Fh3yAWuH7tu" // <- example value
});

At that point, the sources property contains

[
  "../home/jonas/projects/esbuild-sourcemap-example/foo.mjs",
  "../home/jonas/projects/esbuild-sourcemap-example/index.mjs"
]

.. and it becomes impossible to use the sources and determine file locations programmatically without also knowing the build-time CWD and the temporary output directory.

Is there a way to build to a location and retain "nice" and library-friendly values for sources?

Regards

Jonas

[badeball]

FYI, I tried looking into the sourceRoot configuration property, but that didn't appear to changes the sources, but merely append said property to the sourcemap.

[jacobduba]

I am running into the same issue with AWS's SAM CLI. It copies the files to a folder inside /tmp/ before running esbuild. The source maps then end up looking like ../../../../../../../tmp/tmpqnj0qy53/app.ts so line by line debugging does not work. I think the best way to approach this would to have an entryPointSourceMap option that tells esbuild where to point the source maps at.

[Lilja]

I've also happened to experience the same issue. It feels weird that we can't control this prefix since it's wrong when building into a dist directory and the source files are pointing to ../src/<whatever>.

Are there any workarounds to this?

[connorjclark]

A workaround is to use outdir instead of outfile, set write: false, and manually write the results yourself. The map you get will have sources relative to whatever you set for outdir.

[jasonterando]

I am running into the same issue with AWS's SAM CLI. It copies the files to a folder inside /tmp/ before running esbuild. The source maps then end up looking like ../../../../../../../tmp/tmpqnj0qy53/app.ts so line by line debugging does not work. I think the best way to approach this would to have an entryPointSourceMap option that tells esbuild where to point the source maps at.

@jacobduba - did you ever find a workaround that worked with AWS SAM's integrated calls of esbuild?

[jacobduba]

@jasonterando Since AWS SAM moved the code to a tmp directory, I submitted a PR to not move the code to a tmp directory. It fixed the issue but broke some other stuff so the maintainers rejected it.

[jasonterando]

@jacobduba thanks for the reply. For now, I'll stick with calling esbuild from package.json, using nodemon to rebuild upon changes. For AWS SAM and VSCode users, I got the debugger working by configuring launch.json as follows:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Debug (Attach)",
            "request": "attach",
            "address": "localhost",
            "skipFiles": [
                "<node_internals>/**",
                "/var/runtime/*",
                "node_modules/**"
            ],
            "type": "node",
            "port": 5858,
            "remoteRoot": "/var/task",
            "localRoot": "${workspaceFolder}/.aws-sam/build/LambdaApi",
            "sourceMaps": true,
            "sourceMapPathOverrides": {
                "../node_modules/*": "${workspaceFolder}/node_modules/*",
                "../src/*": "${workspaceFolder}/src/*",
            }
        }
    ]
}