Add --nosources option for source maps

[atombrenner]

Context

I am using esbuild to bundle and minify Typescript functions for AWS lambda.

esbuild --bundle --minify --keep-names --sourcemap --platform=node --target=node12

To get meaningful stack traces for exceptions in production, I use the --sourcemap and --keep-names options.
I use NODE_OPTIONS=--enable-source-maps to get a stack trace that uses the source map.
One problem is, that I have to use the --keep-names option to see the original function names in the stack trace.
I guess that it could be related to the missing names field in the generated source map, but I'm not an expert on this topic.

Issue

The --sourcemap option adds the original source to the sourcesContentfield of the source map. This is not necessary for meaningful stack traces, it can be an empty array "sourcesContent": [].

Adding the complete source to the source map thwarts the goal of making the AWS Lamda artifact small
as it doubles the size of the zip package (index.js + index.js.map) I need to upload to AWS Lambda.

I would like an esbuild option --nosources that prevent sources from being included in the source map.
Something similiar to the webpack devtool option nosources-source-map

My current workaround is to post process the generated source map from esbuild and remove the sourcesContent.

[evanw]

Thanks for the detail. Doing this makes sense. Injecting the original source code is by far the heaviest part of the source map, and is only useful in some scenarios.

I think nosources is not the right name because source maps have both a sources field and a sourcesContent field and the intent of the flag is to keep sources but discard sourcesContent. So I'll use a different name instead.

[evanw]

This will be fixed in the next release. Closing.

[p0wl]

wow, awesome, I just ran into exactly this (aws lambda with esbuild via aws-lambda-nodejs), and so happy to found that you added an option for it. Thanks for your work!