Bug 298246 – [CSS] process-css-properties.py gperf warning: 1 input keys have identical hash values, examine output carefully...

• Component: CSS
• Status: RESOLVED FIXED

[David Kilzer (:ddkilzer)]

[CSS] process-css-properties.py gperf warning: 1 input keys have identical hash values, examine output carefully...

```
PhaseScriptExecution Generate\ Derived\ Sources WebKitBuild/WebCore.build/Debug/Derived\ Sources.build/Script-DD041FBD09D9DDBE0010AF2A.sh (in target 'Derived Sources' from project 'WebCore')
    cd Source/WebCore
    /bin/sh -c WebKitBuild/WebCore.build/Debug/Derived\\\ Sources.build/Script-DD041FBD09D9DDBE0010AF2A.sh
ruby WebCore/Scripts/GenerateSettings.rb WebKitBuild/Debug/usr/local/include/wtf/Scripts/Preferences/UnifiedWebPreferences.yaml WebCore/page/Settings.yaml  --template WebCore/Scripts/SettingsTemplates/InternalSettingsGenerated.idl.erb
perl -pe '' WebCore/css/CSSProperties.json > CSSProperties.json
/Applications/Xcode.app/Contents/Developer/Toolchains/OSX26.0.xctoolchain/AppleInternal/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9 "WebCore/css/scripts/process-css-properties.py" --gperf-executable ./gperf --defines "..."
1 input keys have identical hash values, examine output carefully...
```

[Radar WebKit Bug Importer]

<rdar://problem/159680551>

[David Kilzer (:ddkilzer)]

The warning is caused by duplicate aliases of the `font-stretch` alias in `CSSProperties.json`, regardless of the value of `ENABLE_VARIATION_FONTS `:

1. CSS Property: `font-width` (lines 745-788)
```json
"font-width": {
    "codegen-properties": [
        {
            "enable-if": "ENABLE_VARIATION_FONTS",
            "aliases": ["font-stretch"]
        },
        {
            "enable-if": "!ENABLE_VARIATION_FONTS", 
            "aliases": ["font-stretch"]
        }
    ]
}
```

2. CSS Descriptor: `@font-face/font-width` (lines 12626-12662)
```json
"descriptors": {
    "@font-face": {
        "font-width": {
            "codegen-properties": [
                {
                    "enable-if": "ENABLE_VARIATION_FONTS",
                    "aliases": ["font-stretch"]
                },
                {
                    "enable-if": "!ENABLE_VARIATION_FONTS",
                    "aliases": ["font-stretch"]
                }
            ]
        }
    }
}
```

These duplicate aliases result in identical entries in `CSSPropertyNames.gperf`, which then trigger the warning:

```
font-stretch, CSSPropertyID::CSSPropertyFontWidth
font-stretch, CSSPropertyID::CSSPropertyFontWidth
```

[David Kilzer (:ddkilzer)]

Pull request:  https://github.com/WebKit/WebKit/pull/50194

[EWS]

Committed 299518@main (1774fe051f77): <https://commits.webkit.org/299518@main>

Reviewed commits have been landed. Closing PR #50194 and removing active labels.