[3.4] Improve validation in trivia (#5947) (#6046)

Co-authored-by: Vexed <vex@vexcodes.com>

redbot/cogs/trivia/schema.py

@@ -0,0 +1,121 @@
+import itertools
+import re
+from typing import Any, NoReturn
+
+from schema import And, Const, Optional, Schema, SchemaError, SchemaMissingKeyError, Use
+
+from redbot.core.i18n import Translator
+
+__all__ = ("TRIVIA_LIST_SCHEMA", "format_schema_error")
+
+T_ = Translator("Trivia", __file__)
+KEY_ERROR_MSG_RE = re.compile(r"Key '(.+)' error:")
+
+
+class SchemaErrorMessage(str):
+    def format(self, *args: Any, **kwargs: Any) -> str:
+        return T_(str(self))
+
+
+def int_or_float(value: Any) -> float:
+    if not isinstance(value, (float, int)):
+        raise TypeError("Value needs to be an integer or a float.")
+    return float(value)
+
+
+def not_str(value: Any) -> float:
+    if isinstance(value, str):
+        raise TypeError("Value needs to not be a string.")
+    return value
+
+
+_ = SchemaErrorMessage
+NO_QUESTIONS_ERROR_MSG = _("The trivia list does not contain any questions.")
+ALWAYS_MATCH = Optional(Use(lambda x: x))
+MATCH_ALL_BUT_STR = Optional(Use(not_str))
+TRIVIA_LIST_SCHEMA = Schema(
+    {
+        Optional("AUTHOR"): And(str, error=_("{key} key must be a text value.")),
+        Optional("CONFIG"): And(
+            {
+                Optional("max_score"): And(
+                    int,
+                    lambda n: n >= 1,
+                    error=_("{key} key in {parent_key} must be a positive integer."),
+                ),
+                Optional("timeout"): And(
+                    Use(int_or_float),
+                    lambda n: n > 0.0,
+                    error=_("{key} key in {parent_key} must be a positive number."),
+                ),
+                Optional("delay"): And(
+                    Use(int_or_float),
+                    lambda n: n >= 4.0,
+                    error=_(
+                        "{key} key in {parent_key} must be a positive number"
+                        " greater than or equal to 4."
+                    ),
+                ),
+                Optional("bot_plays"): Const(
+                    bool, error=_("{key} key in {parent_key} must be either true or false.")
+                ),
+                Optional("reveal_answer"): Const(
+                    bool, error=_("{key} key in {parent_key} must be either true or false.")
+                ),
+                Optional("payout_multiplier"): And(
+                    Use(int_or_float),
+                    lambda n: n >= 0.0,
+                    error=_("{key} key in {parent_key} must be a non-negative number."),
+                ),
+                Optional("use_spoilers"): Const(
+                    bool, error=_("{key} key in {parent_key} must be either true or false.")
+                ),
+                # This matches any extra key and always fails validation
+                # for the purpose of better error messages.
+                ALWAYS_MATCH: And(
+                    lambda __: False,
+                    error=_("{key} is not a key that can be specified in {parent_key}."),
+                ),
+            },
+            error=_("{key} should be a 'key: value' mapping."),
+        ),
+        str: And(
+            [str, int, bool, float],
+            error=_("Value of question {key} is not a list of text values (answers)."),
+        ),
+        # This matches any extra key and always fails validation
+        # for the purpose of better error messages.
+        MATCH_ALL_BUT_STR: And(
+            lambda __: False,
+            error=_("A key of question {key} is not a text value."),
+        ),
+    },
+    error=_("A trivia list should be a 'key: value' mapping."),
+)
+
+
+def format_schema_error(exc: SchemaError) -> str:
+    if isinstance(exc, SchemaMissingKeyError):
+        return NO_QUESTIONS_ERROR_MSG.format()
+
+    # dict.fromkeys is used for de-duplication with order preservation
+    errors = {idx: msg for idx, msg in enumerate(exc.errors) if msg is not None}
+    if not errors:
+        return str(exc)
+    error_idx, error_msg_fmt = errors.popitem()
+
+    autos = dict.fromkeys(msg for msg in itertools.islice(exc.autos, error_idx) if msg is not None)
+    keys = [match[1] for msg in autos if (match := KEY_ERROR_MSG_RE.fullmatch(msg)) is not None]
+    key_count = len(keys)
+    if key_count == 2:
+        key = keys[-1]
+        parent_key = keys[-2]
+    elif key_count == 1:
+        key = keys[-1]
+        # should only happen for messages where this field isn't used
+        parent_key = "UNKNOWN"
+    else:
+        # should only happen for messages where neither of the fields are used
+        key = parent_key = "UNKNOWN"
+
+    return error_msg_fmt.format(key=repr(key), parent_key=repr(parent_key))