[cache] Refactor to reduced signature.

This brings more robustness to the codebase: users cannot accidentally create file name collisions in the cache dir.

src/pyxu/util/cache.py

@@ -1,26 +1,41 @@
-import pyxu.info.config as config
+import hashlib
+
+import pyxu.info.config as pxcfg
 
 __all__ = [
     "cache_module",
 ]
 
 
-def cache_module(name: str, code: str):
+def cache_module(code: str) -> str:
     """
-    Update a specific module in the dynamic module cache.
+    Save `code` as an importable module in Pyxu's dynamic module cache.
 
     The cached module is updated only if changes are detected.
 
     Parameters
     ----------
-    name: str
-        Name of the module to update.
     code: str
         Contents of the module.
         When stored in a file, `code` should be a valid Python module.
+
+    Returns
+    -------
+    module_name: str
+        Name of the module in :py:func:`~pyxu.info.config.cache_dir`.
+
+    Notes
+    -----
+    `module_name` is chosen automatically based on the file's contents.
     """
-    module_path = config.cache_dir / f"{name}.py"
+    # Compute a unique name
+    h = hashlib.blake2b(code.encode("utf-8"), digest_size=8)
+    module_name = "cached_" + h.hexdigest()
 
+    pxcfg.cache_dir().mkdir(parents=True, exist_ok=True)
+    module_path = pxcfg.cache_dir() / f"{module_name}.py"
+
+    # Do we overwrite?
     write = True
     if module_path.exists():
         with open(module_path, mode="r") as f:
@@ -31,3 +46,5 @@ def cache_module(name: str, code: str):
     if write:
         with open(module_path, mode="w") as f:
             f.write(code)
+
+    return module_name