Deprecate jsonschema.draftN_format_checker attributes.v4.16.0

Format support / enablement will change with vocabulary support,
but in the interim, now that #905 is merged, these objects are
better accessed by retrieving them directly from the corresponding
validator.

In other words: don't do:

    from jsonschema import draft202012_format_checker

just do

    from jsonschema import Draft202012Validator
    do_whatever_with(Draft202012Validator.FORMAT_CHECKER)

5 files changed, 139 insertions, 24 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4c886cf..a64a200 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -3,6 +3,10 @@ v4.16.0
 
 * Improve the base URI behavior when resolving a ``$ref`` to a resolution URI
   which is different from the resolved schema's declared ``$id``.
+* Accessing ``jsonschema.draftN_format_checker`` is deprecated. Instead, if you
+  want access to the format checker itself, it is exposed as
+  ``jsonschema.validators.DraftNValidator.FORMAT_CHECKER`` on any
+  ``jsonschema.protocols.Validator``.
 
 v4.15.0
 =======
diff --git a/docs/validate.rst b/docs/validate.rst
index f949837..9f88259 100644
--- a/docs/validate.rst
+++ b/docs/validate.rst
@@ -181,7 +181,7 @@ By default, no validation is enforced, but optionally, validation can be enabled
     >>> validate(
     ...     instance="-12",
     ...     schema={"format" : "ipv4"},
-    ...     format_checker=draft202012_format_checker,
+    ...     format_checker=Draft202012Validator.FORMAT_CHECKER,
     ... )
     Traceback (most recent call last):
         ...
diff --git a/jsonschema/__init__.py b/jsonschema/__init__.py
index 7e3b91e..6628fc7 100644
--- a/jsonschema/__init__.py
+++ b/jsonschema/__init__.py
@@ -10,15 +10,7 @@ for you.
 """
 import warnings
 
-from jsonschema._format import (
-    FormatChecker,
-    draft3_format_checker,
-    draft4_format_checker,
-    draft6_format_checker,
-    draft7_format_checker,
-    draft201909_format_checker,
-    draft202012_format_checker,
-)
+from jsonschema._format import FormatChecker
 from jsonschema._types import TypeChecker
 from jsonschema.exceptions import (
     ErrorTree,
@@ -56,4 +48,24 @@ def __getattr__(name):
             import importlib_metadata as metadata
 
         return metadata.version("jsonschema")
+
+    format_checkers = {
+        "draft3_format_checker": Draft3Validator,
+        "draft4_format_checker": Draft4Validator,
+        "draft6_format_checker": Draft6Validator,
+        "draft7_format_checker": Draft7Validator,
+        "draft201909_format_checker": Draft201909Validator,
+        "draft202012_format_checker": Draft202012Validator,
+    }
+    ValidatorForFormat = format_checkers.get(name)
+    if ValidatorForFormat is not None:
+        warnings.warn(
+            f"Accessing jsonschema.{name} is deprecated and will be "
+            "removed in a future release. Instead, use the FORMAT_CHECKER "
+            "attribute on the corresponding Validator.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return ValidatorForFormat.FORMAT_CHECKER
+
     raise AttributeError(f"module {__name__} has no attribute {name}")
diff --git a/jsonschema/tests/test_deprecations.py b/jsonschema/tests/test_deprecations.py
index afa2658..54e2267 100644
--- a/jsonschema/tests/test_deprecations.py
+++ b/jsonschema/tests/test_deprecations.py
@@ -162,3 +162,102 @@ class TestDeprecations(TestCase):
         self.assertTrue(
             str(w.warning).startswith("FormatChecker.cls_checks "),
         )
+
+    def test_draftN_format_checker(self):
+        """
+        As of v4.16.0, accessing jsonschema.draftn_format_checker is deprecated
+        in favor of Validator.FORMAT_CHECKER.
+        """
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft202012_format_checker  # noqa
+
+        self.assertIs(
+            draft202012_format_checker,
+            validators.Draft202012Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft202012_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft201909_format_checker  # noqa
+
+        self.assertIs(
+            draft201909_format_checker,
+            validators.Draft201909Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft201909_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft7_format_checker  # noqa
+
+        self.assertIs(
+            draft7_format_checker,
+            validators.Draft7Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft7_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft6_format_checker  # noqa
+
+        self.assertIs(
+            draft6_format_checker,
+            validators.Draft6Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft6_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft4_format_checker  # noqa
+
+        self.assertIs(
+            draft4_format_checker,
+            validators.Draft4Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft4_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertWarns(DeprecationWarning) as w:
+            from jsonschema import draft3_format_checker  # noqa
+
+        self.assertIs(
+            draft3_format_checker,
+            validators.Draft3Validator.FORMAT_CHECKER,
+        )
+        self.assertEqual(w.filename, __file__)
+        self.assertTrue(
+            str(w.warning).startswith(
+                "Accessing jsonschema.draft3_format_checker is ",
+            ),
+            msg=w.warning,
+        )
+
+        with self.assertRaises(ImportError):
+            from jsonschema import draft1234_format_checker  # noqa
diff --git a/jsonschema/tests/test_jsonschema_test_suite.py b/jsonschema/tests/test_jsonschema_test_suite.py
index 43debbb..1e58365 100644
--- a/jsonschema/tests/test_jsonschema_test_suite.py
+++ b/jsonschema/tests/test_jsonschema_test_suite.py
@@ -28,14 +28,14 @@ def skip(message, **kwargs):
     return skipper
 
 
-def missing_format(checker):
+def missing_format(Validator):
     def missing_format(test):  # pragma: no cover
         schema = test.schema
         if (
             schema is True
             or schema is False
             or "format" not in schema
-            or schema["format"] in checker.checkers
+            or schema["format"] in Validator.FORMAT_CHECKER.checkers
             or test.valid
         ):
             return
@@ -150,10 +150,10 @@ TestDraft3 = DRAFT3.to_unittest_testcase(
     DRAFT3.optional_tests_of(name="non-bmp-regex"),
     DRAFT3.optional_tests_of(name="zeroTerminatedFloats"),
     Validator=jsonschema.Draft3Validator,
-    format_checker=jsonschema.draft3_format_checker,
+    format_checker=jsonschema.Draft3Validator.FORMAT_CHECKER,
     skip=lambda test: (
         narrow_unicode_build(test)
-        or missing_format(jsonschema.draft3_format_checker)(test)
+        or missing_format(jsonschema.Draft3Validator)(test)
         or complex_email_validation(test)
         or skip(
             message=bug(),
@@ -175,12 +175,12 @@ TestDraft4 = DRAFT4.to_unittest_testcase(
     DRAFT4.optional_tests_of(name="non-bmp-regex"),
     DRAFT4.optional_tests_of(name="zeroTerminatedFloats"),
     Validator=jsonschema.Draft4Validator,
-    format_checker=jsonschema.draft4_format_checker,
+    format_checker=jsonschema.Draft4Validator.FORMAT_CHECKER,
     skip=lambda test: (
         narrow_unicode_build(test)
         or allowed_leading_zeros(test)
         or leap_second(test)
-        or missing_format(jsonschema.draft4_format_checker)(test)
+        or missing_format(jsonschema.Draft4Validator)(test)
         or complex_email_validation(test)
         or skip(
             message=bug(),
@@ -236,12 +236,12 @@ TestDraft6 = DRAFT6.to_unittest_testcase(
     DRAFT6.optional_tests_of(name="float-overflow"),
     DRAFT6.optional_tests_of(name="non-bmp-regex"),
     Validator=jsonschema.Draft6Validator,
-    format_checker=jsonschema.draft6_format_checker,
+    format_checker=jsonschema.Draft6Validator.FORMAT_CHECKER,
     skip=lambda test: (
         narrow_unicode_build(test)
         or allowed_leading_zeros(test)
         or leap_second(test)
-        or missing_format(jsonschema.draft6_format_checker)(test)
+        or missing_format(jsonschema.Draft6Validator)(test)
         or complex_email_validation(test)
         or skip(
             message=bug(),
@@ -260,12 +260,12 @@ TestDraft7 = DRAFT7.to_unittest_testcase(
     DRAFT7.optional_tests_of(name="float-overflow"),
     DRAFT7.optional_tests_of(name="non-bmp-regex"),
     Validator=jsonschema.Draft7Validator,
-    format_checker=jsonschema.draft7_format_checker,
+    format_checker=jsonschema.Draft7Validator.FORMAT_CHECKER,
     skip=lambda test: (
         narrow_unicode_build(test)
         or allowed_leading_zeros(test)
         or leap_second(test)
-        or missing_format(jsonschema.draft7_format_checker)(test)
+        or missing_format(jsonschema.Draft7Validator)(test)
         or complex_email_validation(test)
         or skip(
             message=bug(),
@@ -408,12 +408,12 @@ TestDraft201909 = DRAFT201909.to_unittest_testcase(
 TestDraft201909Format = DRAFT201909.to_unittest_testcase(
     DRAFT201909.format_tests(),
     Validator=jsonschema.Draft201909Validator,
-    format_checker=jsonschema.draft201909_format_checker,
+    format_checker=jsonschema.Draft201909Validator.FORMAT_CHECKER,
     skip=lambda test: (
         complex_email_validation(test)
         or allowed_leading_zeros(test)
         or leap_second(test)
-        or missing_format(jsonschema.draft201909_format_checker)(test)
+        or missing_format(jsonschema.Draft201909Validator)(test)
         or complex_email_validation(test)
     ),
 )
@@ -533,12 +533,12 @@ TestDraft202012 = DRAFT202012.to_unittest_testcase(
 TestDraft202012Format = DRAFT202012.to_unittest_testcase(
     DRAFT202012.format_tests(),
     Validator=jsonschema.Draft202012Validator,
-    format_checker=jsonschema.draft202012_format_checker,
+    format_checker=jsonschema.Draft202012Validator.FORMAT_CHECKER,
     skip=lambda test: (
         complex_email_validation(test)
         or allowed_leading_zeros(test)
         or leap_second(test)
-        or missing_format(jsonschema.draft202012_format_checker)(test)
+        or missing_format(jsonschema.Draft202012Validator)(test)
         or complex_email_validation(test)
     ),
 )