What Criteria OpenMage CSS/JS Minify Uses to Identify Already Minified Files

OpenMage CSS/JS Minify identifies already-minified files by checking if the filename matches the regular expression [._-](min|pack)\. via the Fballiano_CssjsMinify_Model_Observer::isAlreadyMinified() method, skipping minification to prevent double-processing.

The fballiano/openmage-cssjs-minify extension optimizes Magento and OpenMage storefronts by compressing CSS and JavaScript assets on the fly. To avoid corrupting pre-compressed vendor libraries, the module applies specific filename-based criteria to determine whether an asset has already been minified before processing.

The Filename-Based Detection Criteria

The detection logic centers on a single regular expression that examines the file path for specific naming markers. According to the source code in app/code/community/Fballiano/CssjsMinify/Model/Observer.php at lines 12-15, this criteria distinguishes between raw and pre-minified assets.

The Regex Pattern

The isAlreadyMinified() method uses the following pattern to evaluate filenames:

/[._-](min|pack)\./

This regular expression searches for a dot (.), underscore (_), or hyphen (-) immediately followed by either min or pack, ending with a literal dot before the file extension. When the filename contains sequences like .min., -pack., or _pack., the method returns true.

The isAlreadyMinified() Method

The static method Fballiano_CssjsMinify_Model_Observer::isAlreadyMinified() encapsulates the regex check. This method is called during the http_response_send_before event to screen each asset before minification begins.

Recognized File Naming Conventions

Files matching these criteria are treated as already minified and bypass the minification engine:

• script.min.js — dot separator with "min"
• style.min.css — dot separator with "min"
• vendor-pack.js — hyphen separator with "pack"
• theme_pack.css — underscore separator with "pack"

Any combination of ., _, or - before min or pack satisfies the detection regex used by the observer.

Workflow Implementation

When handling the http_response_send_before event, the observer evaluates each asset path to determine the processing strategy. As implemented in fballiano/openmage-cssjs-minify, the logic branches based on the detection result:

if (self::isAlreadyMinified($path)) {
    // Just copy the original file to the cache folder
    @copy($baseDir . $path, $minifiedDir . $hash);
} else {
    // Run the appropriate minifier (JS or CSS)
    $minifier = new \MatthiasMullie\Minify\JS($baseDir . $path);
    $minifier->minify($minifiedDir . $hash);
}

When isAlreadyMinified() returns true, the file is copied unchanged to the minified cache directory. Otherwise, the asset is processed by the Matthias Mullie minification library to generate the compressed version.

Testing the Detection Criteria Programmatically

Developers can verify the detection logic directly using the observer model to test specific file paths:

$observer = new Fballiano_CssjsMinify_Model_Observer();

$files = [
    '/js/app.min.js',
    '/js/lib.js',
    '/css/theme-pack.css',
    '/css/style.css'
];

foreach ($files as $file) {
    $already = $observer::isAlreadyMinified($file)
        ? 'already minified'
        : 'needs minification';
    echo "$file → $already\n";
}

Output:

/js/app.min.js → already minified
/js/lib.js → needs minification
/css/theme-pack.css → already minified
/css/style.css → needs minification

Summary

• Regex criteria: The extension uses /[._-](min|pack)\./ to test filenames for min or pack markers preceded by ., _, or -.
• Source location: Detection logic resides in Fballiano_CssjsMinify_Model_Observer::isAlreadyMinified() within app/code/community/Fballiano/CssjsMinify/Model/Observer.php (lines 12-15).
• Processing bypass: Matched files are copied unchanged to the cache directory; unmatched files are processed by the Matthias Mullie minifier.
• Naming conventions: Standard patterns like .min., -pack., and _pack. are automatically recognized as already minified.

Frequently Asked Questions

What regex pattern does OpenMage CSS/JS Minify use to detect minified files?

The extension uses the pattern /[._-](min|pack)\./ which looks for a dot, underscore, or hyphen followed by "min" or "pack" immediately before the file extension dot. This regex is hardcoded in the isAlreadyMinified() method and applies to both JavaScript and CSS assets.

Where is the detection logic located in the source code?

The detection logic is implemented in the isAlreadyMinified() method of the Fballiano_CssjsMinify_Model_Observer class, found in app/code/community/Fballiano/CssjsMinify/Model/Observer.php at lines 12-15 according to the repository source.

Does OpenMage CSS/JS Minify check file content or just the filename?

The module checks only the filename against the regex criteria. It does not inspect file contents, headers, or bytecode to determine minification status, relying entirely on naming conventions like .min. or -pack. to identify pre-compressed assets.

What happens when a file is identified as already minified?

When isAlreadyMinified() returns true, the observer copies the original file directly to the minified cache directory without running it through the Matthias Mullie minification library. This preserves the existing compression and avoids potential corruption from double-minification.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}