Since 0.12.17, --watch fail silently when running under lerna

[compulim]

Versions
First repro	0.12.17
Also repro	latest, 0.13, 0.12
Not repro	0.12.16, 0.12.0, 0.11
OS	Ubuntu and Windows
Node/npm	14.17.6/6.14.15 and 16.13.1/8.1.2

When using lerna run <scriptname> --stream to run esbuild --watch with >= 0.12.17, it quit silently. I am using [email protected] (latest), it was released about 10 months ago, which is earlier than 0.12.17.

0.12.16

In the screenshot above, the root package of the monorepo will run [email protected] --watch. ESBuild will say "build finished, watching for changes".

0.12.17

In the screenshot above, I updated to [email protected]. When running it through lerna, ESBuild fail silently and quit immediately. There are no output files produced.

However, when running without --watch (via npm run build), it works without issues, regardless of whether lerna's --parallel and --stream flag is set or not.

Repro

I have prepared a bare minimal repo, https://github.com/compulim/experiment-lerna-esbuild. Please use GitHub Codespaces to try it out on the cloud.

After clone

• Run npm install at root to prepare the repository
• npm start
  • It should start esbuild --version && esbuild src/index.js --bundle --outfile=lib/index.js --watch

ESBuild is located under packages/app. To change version of esbuild:

• cd packages/app
• npm install [email protected]

By default, GitHub Codespaces use Node 14. You can use nvm to change its version.

Workaround

When running esbuild, use concurrently to wrap around it. concurrently will not close stdin on start.

In the bare minimal repo, modify packages/app/package.json:

-    "start": "esbuild --version && esbuild src/index.js --bundle --outfile=lib/index.js --watch"
+    "start": "npx concurrently \"esbuild --version && esbuild src/index.js --bundle --outfile=lib/index.js --watch\""

[evanw]

Watch mode in esbuild is terminated when stdin is closed. Closing stdin indicates to esbuild that you want to end watch mode.

One way to fix this is to change Lerna itself. The ignore here could be changed to inherit instead: https://github.com/lerna/lerna/blob/a47fc294393a3e9507a8207a5a2f07648a524722/core/child-process/index.js#L65.

Another way to fix this is to avoid closing stdin:

diff --git a/packages/app/package.json b/packages/app/package.json
index 5424c2b..2ac3235 100644
--- a/packages/app/package.json
+++ b/packages/app/package.json
@@ -6,7 +6,7 @@
   "main": "lib/index.js",
   "scripts": {
     "build": "esbuild --version && esbuild src/index.js --bundle --outfile=lib/index.js",
-    "start": "esbuild --version && esbuild src/index.js --bundle --outfile=lib/index.js --watch"
+    "start": "esbuild --version && sleep 9999999999 | esbuild src/index.js --bundle --outfile=lib/index.js --watch"
   },
   "author": "",
   "license": "MIT",

[kzc]

Duplicate of #1511

[luwes]

In case you need a cross-platform solution check out ours above, it uses JS setInterval to keep the stdin open until manually stopped.

Changing the stdio in Lerna has some other difficulties seems, comments here:
lerna/lerna#608 (review)