1462669 - Extension dev: Presence of "node_modules" causes very slow extension load

Status: RESOLVED DUPLICATE of bug 1455402

(Firefox :: Untriaged, defect)

Description

[Anthony Lieuallen]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
Build ID: 20180516032328

Steps to reproduce:

Clicked "load temporary add-on" from about:debugging, with some dev-only "node_modules" dependencies in the same directory.


Actual results:

It took >10 seconds of 100% CPU activity for the extension to load.


Expected results:

It should have taken 100-500ms max for the extension to load.


Root cause/STR:

1. Checkout Greasemonkey from
   https://github.com/greasemonkey/greasemonkey.git
2. Launch Firefox nightly, in a blank/fresh profile
   ( 62.0a1 2018-05-18; Built from https://hg.mozilla.org/releases/mozilla-release/rev/afa87f9be3a8852da3a30f286b15ae599c7874f6 )
3. Open about:debuggong
4. "Load Temporary Add-on" and select the code from step 1

Result: Almost instantly (no more than half a second?) the extension loads.  (And its first-run behavior launches a tab.)

In that checked out copy of the code, run "npm install".  Click remove and then load the add-on again.

This time I get ~150% CPU utilization (more than one core), for around ten seconds.  Every time I hit "reload" I get this same delay.  Remove the "node_modules" directory and it's fast again, very sub-second, almost imperceptible delay to reload.

Repeat with Firefox stable (60.0.1; Built from https://hg.mozilla.org/releases/mozilla-release/rev/03d4f76300bedeffd47c726ce7fee0221873da11) and it's fast whether I have a node_modules or not.

Repeat with 61.0b6 ( Built from https://hg.mozilla.org/releases/mozilla-beta/rev/0315d341f73f3385f7bf58f0687d66f621fd9316 ) and it's slow.

So it happened somewhere between 60 and 61b6.


Nothing in the extension code refers to the node_modules directory.  It's only there to power unit testing through commands run in the shell, unrelated to Firefox.  Its presence should not affect how long it takes to load my extension into Firefox.

Comment 1

[Luca Greco [:rpl] [:luca] [:lgreco]]

This may be related to the same underlying issue of Bug 1455402 (computing the size of the addon).

I'm adding Bug 1455402 as a "see also" in the meantime.