Deep dict type-checking x 2.

This commit is the epochal next commit in a commit chain deeply
type-checking *all* **mapping type hints** (e.g., of the form `dict[...,
...]`, `collections.abc.Mapping[..., ...]`,
`collections.abc.MutableMapping[..., ...]`, `typing.Dict[..., ...]`,
`typing.Mapping[..., ...]`, or `typing.MutableMapping[..., ...]`),
en-route to partially resolving long-standing feature requests #167
kindly submitted sometime during my most recent past life by ardent
typing fiend @langfield *and* #2021 kindly submitted sometime during the
past life immediately preceding my most recent past life by Equinor ASA
bear bro @jondequinor (Jonas Grønås). Specifically, this commit improves
internal detection of ignorable type hints so as to be robust against
pernicious edge cases. Although essential, there isn't particularly much
to see here. *Next!* (*Flummoxed ox flambé!*)

beartype/_check/code/snip/codesnipstr.py

@@ -141,6 +141,7 @@
 '''
 
 # ....................{ HINT ~ pep : (484|585) : mapping   }....................
+#FIXME: Refactor us up, please.
 CODE_PEP484585_MAPPING = '''(
 {indent_curr}    # True only if this pith is of this mapping type *AND*...
 {indent_curr}    isinstance({pith_curr_assign_expr}, {hint_curr_expr}) and
@@ -149,18 +150,7 @@
 {indent_curr}        # This mapping is empty *OR*...
 {indent_curr}        not {pith_curr_var_name} or
 {indent_curr}        # This mapping is non-empty. In this case...
-{indent_curr}        (
-{indent_curr}            # Localize the first key of this mapping.
-{indent_curr}            ({pith_curr_key_var_name} := next(iter(
-{indent_curr}                {pith_curr_var_name}))) is {pith_curr_key_var_name} and
-{indent_curr}            # True only if this key satisfies this hint *AND*...
-{indent_curr}            {hint_key_placeholder} and
-{indent_curr}            # Localize the first value of this mapping.
-{indent_curr}            ({pith_curr_value_var_name} := {pith_curr_var_name}[
-{indent_curr}                {pith_curr_key_var_name}]) is {pith_curr_value_var_name} and
-{indent_curr}            # True only if this value satisfies this hint.
-{indent_curr}            {hint_value_placeholder}
-{indent_curr}        )
+{indent_curr}        ({hint_key_and_or_value})
 {indent_curr}    )
 {indent_curr})'''
 '''
@@ -183,6 +173,57 @@
    https://stackoverflow.com/a/70490285/2809027
 '''
 
+
+CODE_PEP484585_MAPPING_KEY_ONLY = '''
+{indent_curr}            # Localize the first key of this mapping.
+{indent_curr}            ({pith_curr_key_var_name} := next(iter(
+{indent_curr}                {pith_curr_var_name}))) is {pith_curr_key_var_name} and
+{indent_curr}            # True only if this key satisfies this hint.
+{indent_curr}            {hint_key_placeholder}'''
+'''
+:pep:`484`- and :pep:`585`-compliant code snippet type-checking *only* the first
+key of the current pith against *only* the key child type hint subscripting a
+parent standard mapping type.
+
+This snippet intentionally avoids type-checking values and is thus suitable for
+type-checking mappings with ignorable value child type hints (e.g.,
+``dict[str, object]``).
+'''
+
+
+CODE_PEP484585_MAPPING_VALUE_ONLY = '''
+{indent_curr}            # Localize the first value of this mapping.
+{indent_curr}            ({pith_curr_value_var_name} := next(iter(
+{indent_curr}                {pith_curr_var_name}.values()))) is {pith_curr_value_var_name} and
+{indent_curr}            # True only if this value satisfies this hint.
+{indent_curr}            {hint_value_placeholder}'''
+'''
+:pep:`484`- and :pep:`585`-compliant code snippet type-checking *only* the first
+value of the current pith against *only* the value child type hint subscripting
+a parent standard mapping type.
+
+This snippet intentionally avoids type-checking keys and is thus suitable for
+type-checking mappings with ignorable key child type hints (e.g.,
+``dict[object, str]``).
+'''
+
+
+CODE_PEP484585_MAPPING_KEY_AND_VALUE = CODE_PEP484585_MAPPING_KEY_ONLY + ''' and
+{indent_curr}            # Localize the first value of this mapping.
+{indent_curr}            ({pith_curr_value_var_name} := {pith_curr_var_name}[
+{indent_curr}                {pith_curr_key_var_name}]) is {pith_curr_value_var_name} and
+{indent_curr}            # True only if this value satisfies this hint.
+{indent_curr}            {hint_value_placeholder}'''
+'''
+:pep:`484`- and :pep:`585`-compliant code snippet type-checking *only* the first
+key-value pair of the current pith against *only* the key and value child type
+hints subscripting a parent standard mapping type.
+
+This snippet intentionally type-checks both keys and values is thus unsuitable
+for type-checking mappings with ignorable key or value child type hints (e.g.,
+``dict[object, str]``, ``dict[str, object]``).
+'''
+
 # ....................{ HINT ~ pep : (484|585) : sequence  }....................
 CODE_PEP484585_SEQUENCE_ARGS_1 = '''(
 {indent_curr}    # True only if this pith is of this sequence type *AND*...

beartype/_check/convert/convsanify.py

@@ -30,6 +30,7 @@
 from beartype._util.cache.map.utilmapbig import CacheUnboundedStrong
 from beartype._util.hint.pep.proposal.pep484585.utilpep484585func import (
     reduce_hint_pep484585_func_return)
+from beartype._util.hint.utilhinttest import is_hint_ignorable
 
 # ....................{ SANIFIERS ~ root                   }....................
 #FIXME: Unit test us up, please.
@@ -263,7 +264,52 @@ def sanify_hint_root_statement(
     return hint
 
 # ....................{ SANIFIERS ~ any                    }....................
-def sanify_hint_any(
+#FIXME: Unit test us up, please.
+def sanify_hint_child_if_unignorable_or_none(*args, **kwargs) -> Any:
+    '''
+    Type hint sanified (i.e., sanitized) from the passed **possibly insane child
+    type hint** (i.e., hint transitively subscripting the root type hint
+    annotating a parameter or return of the currently decorated callable) if
+    this hint is both reducible and ignorable, this hint unmodified if this hint
+    is both irreducible and ignorable, and :data:`None` otherwise (i.e., if this
+    hint is ignorable).
+
+    This high-level sanifier effectively chains the lower-level
+    :func:`sanify_hilt_child` sanifier and
+    :func:`beartype._util.hint.utilhinttest.is_hint_ignorable` tester into a
+    single unified function, streamlining sanification and ignorability
+    detection throughout the codebase.
+
+    Note that a :data:`None` return unambiguously implies this hint to be
+    ignorable, even if the passed hint is itself :data:`None`. Why? Because if
+    the passed hint were :data:`None`, then a :pep:`484`-compliant reducer will
+    internally reduce this hint to ``type(None)``. After reduction, *all* hints
+    are guaranteed to be non-:data:`None`.
+
+    Parameters
+    ----------
+    All passed arguments are passed as is to the lower-level
+    :func:`sanify_hilt_child` sanifier.
+
+    Returns
+    -------
+    object
+        Either:
+
+        * If the passed possibly insane child type hint is ignorable after
+          reduction to a sane child type hint, :data:`None`.
+        * Else, the sane child type hint to which this hint reduces.
+    '''
+
+    # Sane child hint sanified from this possibly insane child hint if this hint
+    # is reducible *OR* this hint as is otherwise (i.e., if irreducible).
+    hint_child = sanify_hint_child(*args, **kwargs)
+
+    # Return either "None" if this hint is ignorable or this hint otherwise.
+    return None if is_hint_ignorable(hint_child) else hint_child
+
+
+def sanify_hint_child(
     # Mandatory parameters.
     hint: object,
     conf: BeartypeConf,
@@ -274,16 +320,16 @@ def sanify_hint_any(
     pith_name: Optional[str] = None,
 ) -> Any:
     '''
-    PEP-compliant type hint sanified (i.e., sanitized) from the passed
-    **PEP-compliant child type hint** (i.e., hint transitively subscripting the
-    root type hint annotating a parameter or return of the currently decorated
-    callable) if this hint is reducible *or* this hint as is otherwise (i.e., if
-    this hint is *not* irreducible).
+    Type hint sanified (i.e., sanitized) from the passed **possibly insane child
+    type hint** (i.e., hint transitively subscripting the root type hint
+    annotating a parameter or return of the currently decorated callable) if
+    this hint is reducible *or* this hint unmodified otherwise (i.e., if this
+    hint is irreducible).
 
     Parameters
     ----------
     hint : object
-        PEP-compliant type hint to be sanified.
+        Type hint to be sanified.
     conf : BeartypeConf
         **Beartype configuration** (i.e., self-caching dataclass encapsulating
         all settings configuring type-checking for the passed object).
@@ -308,7 +354,7 @@ class variable or method annotated by this hint *or* :data:`None`).
     Returns
     -------
     object
-        PEP-compliant type hint sanified from this hint.
+        Type hint sanified from this possibly insane child type hint.
     '''
 
     # This sanifier covers the proper subset of logic performed by the

beartype/_check/error/_errorcause.py

@@ -67,7 +67,7 @@
     is_hint_pep,
     is_hint_pep_args,
 )
-from beartype._check.convert.convsanify import sanify_hint_any
+from beartype._check.convert.convsanify import sanify_hint_child
 from beartype._util.hint.utilhinttest import is_hint_ignorable
 
 # ....................{ CLASSES                            }....................
@@ -266,7 +266,7 @@ def hint(self, hint: Any) -> None:
         # Sanitize this hint if unsupported by @beartype in its current form
         # (e.g., "numpy.typing.NDArray[...]") to another form supported by
         # @beartype (e.g., "typing.Annotated[numpy.ndarray, beartype.vale.*]").
-        hint = sanify_hint_any(
+        hint = sanify_hint_child(
             hint=hint,
             conf=self.conf,
             exception_prefix=self.exception_prefix,

beartype/_check/error/_pep/_pep484585/_errorgeneric.py

@@ -65,7 +65,10 @@ def find_cause_generic(cause: ViolationCause) -> ViolationCause:
     # For each unignorable unerased transitive pseudo-superclass originally
     # declared as an erased superclass of this generic...
     for hint_child in iter_hint_pep484585_generic_bases_unerased_tree(
-        hint=cause.hint, exception_prefix=cause.exception_prefix):
+        hint=cause.hint,
+        conf=cause.conf,
+        exception_prefix=cause.exception_prefix,
+    ):
         # Deep output cause to be returned, permuted from this input cause.
         cause_deep = cause.permute(hint=hint_child).find_cause()
         # print(f'tuple pith: {pith_item}\ntuple hint child: {hint_child}')