Unable to set breakpoints using ES Module syntax

[MichaelGoberling]

Describe the bug
Breakpoints can't be set in VSCode when debugging actions written in ES Module syntax.

Expected behavior
Breakpoints can be set and stopped at by VSCode debugger with actions written in ES Module syntax.

Additional context

• Potential limitation of wskdebug

[moritzraho]

As @shazron mentioned we need to run the transpiled code itself and somehow link it back to the source via source maps

https://github.com/apache/openwhisk-wskdebug/blob/1ec715d98136811bea30eb6a82b378d78e356252/src/kinds/nodejs/nodejs.js#L64-L67
...which brings us to:
https://github.com/apache/openwhisk-wskdebug/blob/1ec715d98136811bea30eb6a82b378d78e356252/src/kinds/nodejs/mount-plain.js#L35

[MichaelGoberling]

Here's a hacky workaround for now:

• Nest your action's index.js in a src folder inside your action folder
• Edit app.config.yaml to point to new action code location
• Add a package.json to new src folder

{
    "type": "module"
}

• Add a webpack-config.js to your action folder:

module.exports = { 
    devtool: 'source-map' 
}

• Add source map location to the debugger config for your action in .vscode/launch.json:

"resolveSourceMapLocations": [
  "${workspaceFolder}/dist/application/actions/<application>/<actionName>-temp/*.js"
]    

• Modify debugger runtime args for your action to pass transpiled file in .vscode/launch.json:

"runtimeArgs": [
  "sequence_test/first",
  "${workspaceFolder}/dist/application/actions/<application>/<actionName>-temp/index.js",
  "-v",
  "--disable-concurrency",
  "--kind",
  "nodejs:16"
]

Note: The steps modifying .vscode/launch.json will have to be run on each subsequent invocation of aio app run as this commands regenerates this config and will overwrite the changes made above

[MichaelGoberling]

I believe what we want is to generate the source map for ESM actions during build time and when we run aio app run, we want to add the source map as part of the launch configuration for the ESM action and modify the debugger runtime args to point to the transpiled file. Thoughts?

[moritzraho]

Nice workaround + investigation. Yes I think that's the approach we should follow. Would need some testing to make sure debugging works as expected with the transpiled file + source maps

[bstopp]

The debugger will still have to allow the root package.json file to have type: module specified.

When i add it to mine, so that i can get the unit tests to work, the debugger results in:

Cannot load module ... Error [ERR_REQUIRE_ESM]: require() of ES Module ... from /nodejsAction/runner.js not supported. index.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which declares all .js files in that package scope as ES modules. Instead rename index.js to end in .cjs, change the requiring code to use dynamic import() which is available in all CommonJS modules, or change "type": "module" to "type": "commonjs" in /code/package.json to treat all .js files as CommonJS (using .mjs for all ES modules instead).

Maybe the transpiled files should end in cjs?

[aiojbot]

JIRA issue created: https://jira.corp.adobe.com/browse/ACNA-1894