Fix OOB in StaticResourcesProcessor for META-INF/resources-only JARs

[LucienBrule]

Fix OOB in StaticResourcesProcessor for META-INF/resources-only JARs

What it does

This patch prevents a StringIndexOutOfBoundsException when a jar contains only the META-INF/resources entry (without any files underneath). Quarkus’ StaticResourcesProcessor was unconditionally calling:

rel.substring(META_INF_RESOURCES.length())

even when rel.equals("META-INF/resources"), which triggers the out-of-bounds error.

How it’s fixed

We now guard on rel.startsWith(prefix) before stripping off the META-INF/resources/ prefix:

if (rel.startsWith(prefix)) {
    String subPath = rel.substring(prefix.length());
    knownPaths.add(new Entry(subPath, false));
}

This safely skips jars that don’t have any static files under META-INF/resources.

Issue

Closes #47666

Verification

I ran the graalpy-demo reproduction script in all modes (break, fix, and verify), and now the native build succeeds without error.

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Thank you for reviewing! 🙏

[maxandersen]

impressive we haven't seen this elsewhere :)

lgtm.

[quarkus-bot]

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