Bug: Memory Leak with watch mode `--watch=true`

[mxschmitt]

Reproduction:

1. git clone https://github.com/microsoft/playwright && cd playwright
2. npm ci
3. npx esbuild --log-level=verbose "packages/playwright-core/src/**/*.ts" --outdir=packages/playwright-core/lib --sourcemap=linked --watch=true --platform=node --format=cjs
4. Go to packages/playwright-core/src/client/page.ts and modify the file header 20 times, between each time save the file and look at the memory consumption.

This can be used as well:

import fs from "fs"
for (let i = 0; i < 100; i++) {
  fs.appendFileSync("packages/playwright-core/src/client/page.ts", "\n")
  await new Promise((resolve) => setTimeout(resolve, 50))
}

and aborted after a few seconds.

Expected: It stays around 50-200 MB
Actual: It grows up to 10-40 GB

Version: 0.25.0 - also tested with 0.25.2

I was able to reproduce on macOS and Linux (Ubuntu amd64).

[mxschmitt]

Investigation:

• We are doing --watch=true
• Internally if --watch is not passed, GC is disabled as per here:

  • esbuild/cmd/esbuild/main.go

    Line 316 in 44e7469

    debug.SetGCPercent(-1)

• Changing it from --watch=true to --watch fixes it

[mxschmitt]

Potential fix if you are interested in aligning it with the cli_impl.go parser:

diff --git a/cmd/esbuild/main.go b/cmd/esbuild/main.go
index 74ced83a..0aa3dd43 100644
--- a/cmd/esbuild/main.go
+++ b/cmd/esbuild/main.go
@@ -222,11 +222,11 @@ func main() {
 			// This may be a reasonable thing to do in a short-lived VM where all
 			// processes in the VM are only started once and then the VM is killed
 			// when the processes are no longer needed.
-			if arg == "--watch" {
-				isWatch = true
-			} else if arg == "--watch=forever" {
+			if arg == "--watch=forever" {
 				arg = "--watch"
 				isWatchForever = true
+			} else if strings.HasPrefix(arg, "--watch") {
+				isWatch = true
 			}
 
 			// Strip any arguments that were handled above
@@ -300,7 +300,7 @@ func main() {
 			for _, arg := range osArgs {
 				if !strings.HasPrefix(arg, "-") {
 					nonFlagCount++
-				} else if arg == "--serve" || arg == "--watch" || strings.HasPrefix(arg, "--serve=") {
+				} else if arg == "--watch" || strings.HasPrefix(arg, "--watch=") || arg == "--serve" || strings.HasPrefix(arg, "--serve=") {
 					isServeOrWatch = true
 				}
 			}

feel free to close otherwise.

[evanw]

Thanks for figuring this out, and for the PR. Quite a dumb bug. I'll include the fix for this in the next release.