ember build modifies node_modules by populating esm cache

[chancancode]

Reproduction

/tmp ❯❯❯ ember new --yarn zomg
installing app
Ember CLI v3.22.0

✨  Creating a new Ember app in /private/tmp/zomg:
  create .editorconfig
  create .ember-cli
  create .eslintignore
  create .eslintrc.js
  create .template-lintrc.js
  create .travis.yml
  create .watchmanconfig
  create README.md
  create app/app.js
  create app/components/.gitkeep
  create app/controllers/.gitkeep
  create app/helpers/.gitkeep
  create app/index.html
  create app/models/.gitkeep
  create app/router.js
  create app/routes/.gitkeep
  create app/styles/app.css
  create app/templates/application.hbs
  create config/ember-cli-update.json
  create config/environment.js
  create config/optional-features.json
  create config/targets.js
  create ember-cli-build.js
  create .gitignore
  create package.json
  create public/robots.txt
  create testem.js
  create tests/helpers/.gitkeep
  create tests/index.html
  create tests/integration/.gitkeep
  create tests/test-helper.js
  create tests/unit/.gitkeep
  create vendor/.gitkeep

🚧  Installing packages... This might take a couple of minutes.
Yarn: Installed dependencies

🎥  Initializing git repository.
Git: successfully initialized.

🎉  Successfully created project zomg.
👉   Get started by typing:

  $ cd zomg
  $ yarn start

Happy coding!
/tmp ❯❯❯ cd zomg
/t/zomg ❯❯❯ sed -i '' '/node_modules/d' .gitignore
/t/zomg ❯❯❯ git diff
diff --git a/.gitignore b/.gitignore
index c40a1b2..bb2b3da 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,7 +6,6 @@

 # dependencies
 /bower_components/
-/node_modules/

 # misc
 /.env*
@@ -20,6 +19,5 @@
 /yarn-error.log

 # ember-try
-/.node_modules.ember-try/
 /bower.json.ember-try
 /package.json.ember-try
/t/zomg ❯❯❯ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   .gitignore

Untracked files:
  (use "git add <file>..." to include in what will be committed)

	node_modules/

no changes added to commit (use "git add" and/or "git commit -a")
/t/zomg ❯❯❯ git add .
/t/zomg ❯❯❯ git commit -m "snapshot node_modules"
Auto packing the repository in background for optimum performance.
See "git help gc" for manual housekeeping.
[master 13798b2] snapshot node_modules
 34523 files changed, 3573631 insertions(+), 2 deletions(-)
/t/zomg ❯❯❯ ember build
Environment: development
cleaning up...
Built project successfully. Stored in "dist/".
/t/zomg ❯❯❯ git status
On branch master
Untracked files:
  (use "git add <file>..." to include in what will be committed)

	node_modules/@ember-data/private-build-infra/node_modules/.cache/
	node_modules/esm/node_modules/

nothing added to commit but untracked files present (use "git add" to track)
/t/zomg ❯❯❯ tree node_modules/@ember-data/private-build-infra/node_modules/.cache/
node_modules/@ember-data/private-build-infra/node_modules/.cache/
└── esm
    ├── addd920c128a19ba.js
    └── d0446dc2128a19ba.js

1 directory, 2 files

Description

After a ember build, ember data adds extra files to the node_modules directory.

Versions

I think this has been an issue for the last few versions at least, but this was tested using 3.22

[snewcomer]

ref #7322

[chancancode]

Hmm it seems like that PR should have been included in 3.22 right?

[snewcomer]

In my testing, this cache was always created (just tested on 3.18). { cache: false } was meant to avoid using that cache at run time. I have not yet seen a way to avoid creating the cache and am not sure if this is a bug or the feature.

https://github.com/standard-things/esm#devopts

As a side note, I noticed some potential bugs with esm.

Current

With
process.env.ESM_DISABLE_CACHE = true as well as { cache: false }.

So we are still creating something.

I think there is still some investigation here.

[rwjblue]

Since Node 12 and higher support modules natively, maybe we should look into use the native support when we can (and fallback to esm).

[runspired]

I recently did some work requiring interop of native modules with cjs modules for node-12. Said interop requires using the experimental modules support flag when running the script and importing via await import() to get it working. I don't think we can do this considering this script runs for end users until node > 12 since we can't ask them to always run things with the flag.

[NullVoxPopuli]

the existence of esm prevents ember-data from being used on stackblitz (See #8021 (and related issues))