Grunt uglify:core and copy:files tasks hang when wp-content has many files

[westonruter]

For a long time, I've struggled with npm run build:dev (see ​Slack thread). When I run the command, it would always seem to hang at:

Running "uglify:core" (uglify) task

I got so fed up with having to wait so long at that task, that I started resorting to ​using symlinks to avoid having to do a build altogether.

A note on my development environment setup: I clone the repos for the plugins and themes I work on into the wp-content of my wordpress-develop clone which I use for core development.

I got fed up and decided to put Gemini CLI on the problem and it came up with this fix:

Gruntfile.js

@@ -926 +926 @@
                                         'wp-includes/js/tinymce/plugins/wp*/plugin.js',
 
                                         // Exceptions.
-                                        '!**/*.min.js',
+                                        '!{wp-admin,wp-includes}/**/*.min.js',
                                         '!wp-admin/js/custom-header.js', // Why? We should minify this.
                                         '!wp-admin/js/farbtastic.js',
                                         '!wp-includes/js/wp-emoji-loader.js', // This is a module. See the emoji-loader task below.

The hang was caused by a broad exclusion pattern in the uglify:core task within Gruntfile.js. Its explanation makes perfect sense:

When you run npm run build:dev, the cwd (current working directory) for the build tasks is set to src/.

The original pattern !**/*.min.js told Grunt to exclude any minified files found anywhere inside the src/ directory. To fulfill this request, the globbing engine had to scan every single folder and file within src/ to see if they matched.

Because your src/wp-content/ directory contains several plugins (like the jetpack-monorepo) with massive node_modules folders containing hundreds of thousands of files, Grunt would hang for a long time just trying to find all those files to ensure they were excluded.

By changing the pattern to !{wp-admin,wp-includes}/**/*.min.js, I restricted that exclusion search to only the core wp-admin and wp-includes directories. This allows Grunt to completely skip scanning the wp-content directory, which resolves the hang.

Impact

When running npm run build:dev:

Before: 43.032s
After: 9.393s

This is now >4.5 times faster, a >78% reduction in execution time!

The uglify:core task utilizes a negative glob pattern !**/*.min.js to prevent re-minifying already minified files. In development builds (npm run build:dev), this pattern operates relative to the src/ directory. Consequently, the glob expansion scans the entire src/ directory tree, including wp-content.

For environments where wp-content contains deep directory structures—such as plugins with node_modules dependencies—this traversal becomes prohibitively slow, causing the build process to hang.

This change scopes the exclusion pattern to !{wp-admin,wp-includes}/**/*.min.js, limiting the file scan to the relevant core directories and preventing unnecessary recursion into wp-content.

Trac ticket: https://core.trac.wordpress.org/ticket/64563

[mukesh27]

Replying to westonruter:

Impact

When running npm run build:dev:

Before: 43.032s
After: 9.393s

This is now >4.5 times faster, a >78% reduction in execution time!

Go for it 🚀

I asked Gemini if there were any other opportunities to improve performance similarly in Gruntfile.js, and it identified another glob pattern in copy:files. Indeed, when I run npm run build I find it hangs for a long time at:

Running "copy:files" (copy) task

However, with c413206 the time to build is dramatically improved:

Before: 51.102s
After: 13.805s

[westonruter]

In 61545:

Build/Test Tools: Optimize uglify:core and copy:files glob patterns in Grunt tasks.

The uglify:core and copy:files tasks utilized broad negative glob patterns (!**/*.min.js and !**/*.map) to exclude files from processing. The glob expansion scans the entire src/ directory tree, including wp-content. For environments where wp-content contains deep directory structures (such as plugins with node_modules dependencies) this traversal becomes prohibitively slow, causing the build process to hang.

This change scopes the exclusion patterns to specific directories (e.g. wp-admin, wp-includes, default themes, and Akismet), limiting the file scan to relevant core paths and preventing unnecessary recursion into wp-content.

In one dev environment, this reduces npm run build:dev from 43s to 9s, and npm run build from 51s to 13s.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/10809

Follow up to [61475].

Props westonruter, jonsurrell.
See #63606.
Fixes #64563.