Reiterables x 8.

This commit is the next in a commit chain deeply type-checking
**reiterables** (i.e., collections satisfying the
`collections.abc.Collection` protocol with guaranteed `O(1)` read-only
access to *only* the first collection item), en-route to *finally*
resolving feature request #167 kindly submitted by the perennial
brilliant @langfield (...*how I miss that awesome guy!*) several
lifetimes ago back when I was probably a wandering vagabond Buddhist
monk with a bad attitude, a begging bowl the size of my emaciated torso,
and an honestly pretty cool straw hat that glinted dangerously in the
firelight. Note that reiterables include *all* containers matched by one
or more of the following PEP 484- or 585-compliant type hints:

* `frozenset[...]`.
* `set[...]`.
* `collections.deque[...]`.
* `collections.abc.Collection[...]`.
* `collections.abc.KeysView[...]`.
* `collections.abc.MutableSet[...]`.
* `collections.abc.Set[...]`.
* `collections.abc.ValuesView[...]`.
* `typing.AbstractSet[...]`.
* `typing.Collection[...]`.
* `typing.Deque[...]`.
* `typing.FrozenSet[...]`.
* `typing.KeysView[...]`.
* `typing.MutableSet[...]`.
* `typing.Set[...]`.
* `typing.ValuesView[...]`.

Specifically, this commit continues reducing problematic DRY (Don't
Repeat Yourself) violations in @beartype's internal type-checking code
generator. (*Etude of interminable terminus of vermin in verisimilitude!*)

beartype/_check/code/snip/codesnipstr.py

@@ -12,13 +12,7 @@
 '''
 
 # ....................{ IMPORTS                            }....................
-from beartype.typing import Dict
-from beartype._check.checkmagic import VAR_NAME_RANDOM_INT
-from beartype._data.hint.datahinttyping import (
-    CallableStrFormat,
-    HintSignToCallableStrFormat,
-)
-from beartype._data.hint.pep.sign.datapepsigncls import HintSign
+from beartype._data.hint.datahinttyping import CallableStrFormat
 
 # ....................{ HINT ~ placeholder : child         }....................
 CODE_HINT_CHILD_PLACEHOLDER_PREFIX = '@['
@@ -246,94 +240,6 @@
 ``dict[object, str]``, ``dict[str, object]``).
 '''
 
-# ....................{ HINT ~ pep : (484|585) : reiterable  }....................
-#FIXME: Excise after enabling the
-#"HINT_SIGN_PEP484585_CONTAINER_ARGS_1_TO_CODE_format" global, please.
-CODE_PEP484585_REITERABLE_ARGS_1 = '''(
-{indent_curr}    # True only if this pith is of this reiterable type *AND*...
-{indent_curr}    isinstance({pith_curr_assign_expr}, {hint_curr_expr}) and
-{indent_curr}    # True only if either this reiterable is empty *OR* this reiterable
-{indent_curr}    # is both non-empty and the first item satisfies this hint.
-{indent_curr}    (not {pith_curr_var_name} or {hint_child_placeholder})
-{indent_curr})'''
-'''
-:pep:`484`- and :pep:`585`-compliant code snippet type-checking the current pith
-against a parent **standard reiterable type** (i.e., type hint subscripted by
-exactly one child type hint constraining *all* items of this pith, which
-necessarily satisfies the :class:`collections.abc.Collection` protocol with
-guaranteed :math:`O(1)` read-only access to *only* the first collection item).
-
-See Also
---------
-:data:`beartype._data.hint.pep.sign.datapepsignset.HINT_SIGNS_REITERABLE_ARGS_1`
-    Further commentary on reiterables.
-'''
-
-
-#FIXME: Excise after enabling the
-#"HINT_SIGN_PEP484585_CONTAINER_ARGS_1_TO_CODE_format" global, please.
-CODE_PEP484585_REITERABLE_ARGS_1_PITH_CHILD_EXPR = (
-    '''next(iter({pith_curr_var_name}))''')
-'''
-:pep:`484`- and :pep:`585`-compliant Python expression efficiently yielding the
-first item of the current reiterable pith.
-'''
-
-# ....................{ HINT ~ pep : (484|585) : sequence  }....................
-#FIXME: Excise after enabling the
-#"HINT_SIGN_PEP484585_CONTAINER_ARGS_1_TO_CODE_format" global, please.
-CODE_PEP484585_SEQUENCE_ARGS_1 = '''(
-{indent_curr}    # True only if this pith is of this sequence type *AND*...
-{indent_curr}    isinstance({pith_curr_assign_expr}, {hint_curr_expr}) and
-{indent_curr}    # True only if either this sequence is empty *OR* this sequence
-{indent_curr}    # is both non-empty and a random item satisfies this hint.
-{indent_curr}    (not {pith_curr_var_name} or {hint_child_placeholder})
-{indent_curr})'''
-'''
-:pep:`484`- and :pep:`585`-compliant code snippet type-checking the current pith
-against a parent **standard sequence type** (i.e., type hint subscripted by
-exactly one child type hint constraining *all* items of this pith, which
-necessarily satisfies the :class:`collections.abc.Sequence` protocol with
-guaranteed :math:`O(1)` indexation across all sequence items).
-
-Caveats
--------
-**This snippet cannot contain ternary conditionals.** For unknown reasons
-suggesting a critical defect in the current implementation of Python 3.8's
-assignment expressions, this snippet raises :class:`UnboundLocalError`
-exceptions resembling the following when this snippet contains one or more
-ternary conditionals:
-
-    UnboundLocalError: local variable '__beartype_pith_1' referenced before assignment
-
-In particular, the initial draft of this snippet guarded against empty
-sequences with a seemingly reasonable ternary conditional:
-
-.. code-block:: python
-
-   CODE_PEP484585_SEQUENCE_ARGS_1 = \'\'\'(
-   {indent_curr}    isinstance({pith_curr_assign_expr}, {hint_curr_expr}) and
-   {indent_curr}    {hint_child_placeholder} if {pith_curr_var_name} else True
-   {indent_curr})\'\'\'
-
-That should behave as expected, but doesn't, presumably due to obscure scoping
-rules and a non-intuitive implementation of ternary conditionals in CPython.
-Ergo, the current version of this snippet guards against empty sequences with
-disjunctions and conjunctions (i.e., ``or`` and ``and`` operators) instead.
-Happily, the current version is more efficient than the equivalent approach
-based on ternary conditional (albeit slightly less intuitive).
-'''
-
-
-#FIXME: Excise after enabling the
-#"HINT_SIGN_PEP484585_CONTAINER_ARGS_1_TO_CODE_format" global, please.
-CODE_PEP484585_SEQUENCE_ARGS_1_PITH_CHILD_EXPR = (
-    f'''{{pith_curr_var_name}}[{VAR_NAME_RANDOM_INT} % len({{pith_curr_var_name}})]''')
-'''
-:pep:`484`- and :pep:`585`-compliant Python expression yielding the value of a
-randomly indexed item of the current sequence pith.
-'''
-
 # ....................{ HINT ~ pep : (484|585) : tuple     }....................
 CODE_PEP484585_TUPLE_FIXED_PREFIX = '''(
 {indent_curr}    # True only if this pith is a tuple.
@@ -613,14 +519,6 @@
     CODE_PEP484585_MAPPING_VALUE_ONLY_PITH_CHILD_EXPR.format)
 CODE_PEP484585_MAPPING_KEY_VALUE_PITH_CHILD_EXPR_format: CallableStrFormat = (
     CODE_PEP484585_MAPPING_KEY_VALUE_PITH_CHILD_EXPR.format)
-CODE_PEP484585_REITERABLE_ARGS_1_format: CallableStrFormat = (
-    CODE_PEP484585_REITERABLE_ARGS_1.format)
-CODE_PEP484585_REITERABLE_ARGS_1_PITH_CHILD_EXPR_format: CallableStrFormat = (
-    CODE_PEP484585_REITERABLE_ARGS_1_PITH_CHILD_EXPR.format)
-CODE_PEP484585_SEQUENCE_ARGS_1_format: CallableStrFormat = (
-    CODE_PEP484585_SEQUENCE_ARGS_1.format)
-CODE_PEP484585_SEQUENCE_ARGS_1_PITH_CHILD_EXPR_format: CallableStrFormat = (
-    CODE_PEP484585_SEQUENCE_ARGS_1_PITH_CHILD_EXPR.format)
 CODE_PEP484585_SUBCLASS_format: CallableStrFormat = (
     CODE_PEP484585_SUBCLASS.format)
 CODE_PEP484585_TUPLE_FIXED_EMPTY_format: CallableStrFormat = (

beartype/_check/error/_pep/pep484585/errpep484585sequence.py

@@ -58,9 +58,8 @@ def find_cause_sequence_args_1(cause: ViolationCause) -> ViolationCause:
     # Assert this hint was subscripted by the expected number of child type
     # hints. Note that prior logic should have already guaranteed this.
     assert len(cause.hint_childs) in hints_child_len_expected, (
-        f'Sequence hint {repr(cause.hint)} subscripted by '
-        f'{len(cause.hint_childs)} != {hints_child_len_expected} '
-        f'child type hints.'
+        f'Sequence type hint {repr(cause.hint)} number of child type hints '
+        f'{len(cause.hint_childs)} not in {hints_child_len_expected}.'
     )
 
     # First child hint subscripting this parent sequence hint. All remaining
@@ -137,8 +136,7 @@ def find_cause_sequence_args_1(cause: ViolationCause) -> ViolationCause:
         # Deep output cause describing the failure of this item to satisfy this
         # child hint if this item violates this child hint *OR* "None" otherwise
         # (i.e., if this item satisfies this child hint).
-        cause_deep = cause.permute(
-            pith=pith_item, hint=hint_child).find_cause()
+        cause_deep = cause.permute(pith=pith_item, hint=hint_child).find_cause()
 
         # If this item is the cause of this failure...
         if cause_deep.cause_str_or_none is not None:

beartype/_check/error/errget.py

@@ -12,6 +12,44 @@
 '''
 
 # ....................{ TODO                               }....................
+#FIXME: [DESIGN] The external
+#"beartype._check.checkmagic.ARG_NAME_GET_VIOLATION" hidden parameter is
+#inefficient in both time and space. Now that we unconditionally pass
+#"ARG_NAME_CHECK_META" to *ALL* wrapper functions, we should instead:
+#* Rename "ARG_NAME_CHECK_META" to "ARG_NAME_ERROR_META".
+#* Define a new "beartype._check.error.errmeta" submodule.
+#* Rename the existing "beartype._check.metadata.metacheck.BeartypeCheckMeta"
+#  dataclass into a new "beartype._check.error.errmeta.BeartypeErrorMeta"
+#  full-blown class.
+#* Remove the "beartype._check.metadata.metacheck" submodule.
+#* Refactor *ALL* public methods defined below into methods of that class --
+#  which then simply accesses the instance variables of this class rather than
+#  having those instance variables be externally passed. To do so sanely, we
+#  might consider:
+#* Refactor the get_func_pith_violation() function defined below into a new
+#  get_func_pith_violation() method of "BeartypeErrorMeta" with signature
+#  resembling:
+#    class BeartypeErrorMeta(object):
+#        ...
+#        def get_func_pith_violation(
+#            self,
+#
+#            # Mandatory parameters.
+#            pith_name: str,
+#            pith_value: object,
+#
+#            # Optional keyword parameters.
+#            **kwargs
+#        ) -> Exception:
+#* Remove the "beartype._check.checkmagic.ARG_NAME_GET_VIOLATION" global.
+#* Refactor all snippets referencing "ARG_NAME_GET_VIOLATION" to instead
+#  reference "ARG_NAME_ERROR_META".
+#
+#Oh... wait. That last point is the sticking point, huh? Refactoring those
+#snippets isn't quite so easy, sadly. We reference "ARG_NAME_GET_VIOLATION" for
+#a reason. Doing so allows us to trivially switch between various competing
+#getter functions defined by this submodule. Oh, well. We shrug! *shrug*
+
 #FIXME: [ACCESS] Generalizing the "random_int" concept (i.e., the optional
 #"random_int" parameter accepted by the get_func_pith_violation() function) that
 #enables O(1) exception handling to containers that do *NOT* provide efficient
@@ -63,6 +101,11 @@
 #  over all container items in O(n) brute-force time. Obviously, extreme care
 #  must be taken here to ensure that this exception handling algorithm visits
 #  containers in the exact same order as visited by our testing algorithm.
+#FIXME: *UHH.* I honestly have *NO* idea what any of the above is on about. It's
+#likely we overthought the above commentary to extreme overkill. Notably,
+#@beartype does (in fact) now deeply type-check both maps and sets. Works great,
+#actually. No need for any of the above insanity, either. Let's re-read this
+#and, if bollocks, excise all of the above. Overkill, thy name is that "FIXME:".
 
 #FIXME: [COLOR] The call to the strip_text_ansi() function below is inefficient
 #and thus non-ideal. Since efficiency isn't a pressing concern in an exception