Play Framework

fix(classloading): start from a warm tmp/bytecode in an application with package-info classes (PF-186)

Every play run but the first finds the application's classes in
tmp/bytecode, and in an application with a package-info in its packages
that start failed: IllegalArgumentException from ClassLoader.definePackage,
a 500 for the request that started it. The start that compiles from source
never showed it.

A package-info read from the cache is defined without being compiled,
because the DEV batch compile covers only ordinary classes. So
isDefinable() never held for it, and the findLoadedClass check at the top
of doLoadApplicationClass leaves package-info names out. A class of the
package loads it first through loadPackage; when getAllClasses then
reached the package-info itself, it defined its package again. Guarding
definePackage alone does not help: the next failure is a LinkageError for
a duplicate definition of the package-info class. The loader now returns a
package-info it has already defined. The precompiled path had its own
findLoadedClass check and is unchanged.

The same gap left such a package-info with no timestamp, which only
compiled() records, so the next request's detectChanges took every one for
edited: it recompiled each, rewrote its cache file, emptied the
application's caches and hot-swapped it, or restarted the application
when no agent was loaded. A class defined from the cache now records its
file's timestamp when no compile has. The cache answers only when the
hash of the current source matches, so the bytes are known to match the
file, and an edit made later is still found.

PackageInfoBytecodeCacheTest boots a scratch application with four
package-info packages twice in child JVMs. It fails without either change,
and also with a timestamp that would hide later edits. Against a server
started as play run starts it, the second launch's first request was a
500 before the fix and serves now, and its second request rewrites no
cache file where it rewrote four.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>