First pass at an explicit list of (non-)public API

docs/changes.rst

@@ -2,6 +2,12 @@
 Changelog
 =========
 
+v0.26.3
+-------
+
+* Add some documentation on ``referencing`` public and non-public API.
+
+
 v0.26.2
 -------
 

docs/compatibility.rst

@@ -0,0 +1,25 @@
+=============
+Compatibility
+=============
+
+``referencing`` is currently in beta so long as version numbers begin with a ``0``, meaning its public interface may change if issues are uncovered, though not typically without reason.
+Once it seems clear that the interfaces look correct (likely after ``referencing`` is in use for some period of time) versioning will move to `CalVer <https://calver.org/>`_ and interfaces will not change in backwards-incompatible ways without deprecation periods.
+
+In the spirit of `having some explicit detail on Bowtie's public interfaces <regret:before-you-deprecate:document your public api>`, here is a non-exhaustive list of things which are *not* part of the ``referencing`` public interface, and therefore which may change without warning, even once no longer in beta:
+
+* All commonly understood indicators of privacy in Python -- in particular, (sub)packages, modules and identifiers beginning with a single underscore.
+  In the case of modules or packages, this includes *all* of their contents recursively, regardless of their naming.
+* All contents in the ``referencing.tests`` package unless explicitly indicated otherwise
+* The precise contents and wording of exception messages raised by any callable, private *or* public.
+* The precise contents of the ``__repr__`` of any type defined in the package.
+* The ability to *instantiate* exceptions defined in `referencing.exceptions`, with the sole exception of those explicitly indicating they are publicly instantiable (notably `referencing.exceptions.NoSuchResource`).
+* The instantiation of any type with no public identifier, even if instances of it are returned by other public API.
+  E.g., `referencing._core.Resolver` is not publicly exposed, and it is not public API to instantiate it in ways other than by calling `referencing.Registry.resolver` or an equivalent.
+  All of its public attributes are of course public, however.
+* Any identifiers in any modules which are imported from other modules.
+  In other words, if ``referencing.foo`` imports ``bar`` from ``referencing.quux``, it is *not* public API to use ``referencing.foo.bar``; only ``referencing.quux.bar`` is public API.
+  This does not apply to any objects exposed directly on the ``referencing`` package (e.g. `referencing.Resource`), which are indeed public.
+* Subclassing of any class defined throughout the package.
+  Doing so is not supported for any object, and in general most types will raise exceptions to remind downstream users not to do so.
+
+If any API usage may be questionable, feel free to open a discussion (or issue if appropriate) to clarify.

docs/conf.py

@@ -101,11 +101,12 @@ def entire_domain(host):
 intersphinx_mapping = {
     "hatch": ("https://hatch.pypa.io/latest/", None),
     "jsonschema-specifications": (
-        "https://jsonschema-specifications.readthedocs.io/en/latest/",
+        "https://jsonschema-specifications.readthedocs.io/en/stable/",
         None,
     ),
+    "regret": ("https://regret.readthedocs.io/en/stable/", None),
     "python": ("https://docs.python.org/", None),
-    "setuptools": ("https://setuptools.pypa.io/en/latest/", None),
+    "setuptools": ("https://setuptools.pypa.io/en/stable/", None),
 }
 
 # -- extlinks --

docs/index.rst

@@ -11,3 +11,4 @@ In other words, a way for e.g. JSON Schema tooling to resolve the ``$ref`` keywo
     schema-packages
     api
     changes
+    compatibility

docs/spelling-wordlist.txt

@@ -7,11 +7,14 @@ dereferenced
 deserialized
 discoverability
 filesystem
+instantiable
+instantiation
 metaschemas
 referenceable
 resolvers
 runtime
 schemas
+subclassing
 submodules
 subresource
 subresources

referencing/exceptions.py

@@ -18,6 +18,9 @@
 class NoSuchResource(KeyError):
     """
     The given URI is not present in a registry.
+
+    Unlike most exceptions, this class *is* intended to be publicly
+    instantiable and *is* part of the public API of the package.
     """
 
     ref: URI