Add configure() and DISKCACHE_DISK so caches created without a disk use a process-wide default, with an explicit disk always winning

[avgvi]

Adds a process-wide default disk, so an application can turn on SafeDisk for caches that libraries create for it without patching those libraries.

• configure(disk) sets the disk type of every Cache, FanoutCache, Deque, Index and DjangoCache created afterwards without a disk, returns the previous setting, and configure(None) clears it. default_disk() returns the type in effect.
• Without configure, the environment decides: DISKCACHE_DISK=safe selects SafeDisk, with DISKCACHE_SAFE_TYPES (import paths) and DISKCACHE_SAFE_MODULES (module names) passed to SafeDisk.with_types; DISKCACHE_DISK also takes default or the import path of a disk class. Invalid values raise ValueError naming the variable.
• Precedence: an explicit disk= argument, then configure, then the environment, then Disk. Libraries that pass their own disk keep it, caches that already exist keep theirs, and nothing is written to the cache directory.
• The disk arguments of Cache, FanoutCache, Deque, Index and the Django DISK option now default to None, meaning that type.
• Tests in tests/test_default_disk.py for every container, the precedence, the environment forms and errors, pickled caches and persistence.

Stacked on #23.

Verified: 484 tests pass on Python 3.12; blue, isort, flake8, mypy, doc8 and the Sphinx build with warnings as errors pass.

[read-the-docs-community]

Documentation build overview

📚 diskcache-community | 🛠️ Build #35226541 | 📁 Comparing dc35bfd against latest (823b63a)

  🔍 Preview build  

7 files changed · ± 7 modified

± Modified

• api.html
• case-study-landing-page-caching.html
• case-study-web-crawler.html
• djangocache-benchmarks.html
• genindex.html
• index.html
• tutorial.html