diff --git a/singer_sdk/_singerlib/catalog.py b/singer_sdk/_singerlib/catalog.py
index 77fe884d8..87b528466 100644
--- a/singer_sdk/_singerlib/catalog.py
+++ b/singer_sdk/_singerlib/catalog.py
@@ -31,11 +31,7 @@ def __missing__(self, breadcrumb: Breadcrumb) -> bool:
         Returns:
             True if the breadcrumb is selected, False otherwise.
         """
-        if len(breadcrumb) >= 2:  # noqa: PLR2004
-            parent = breadcrumb[:-2]
-            return self[parent]
-
-        return True
+        return self[breadcrumb[:-2]] if len(breadcrumb) >= 2 else True  # noqa: PLR2004
 
 
 @dataclass
@@ -71,7 +67,7 @@ def from_dict(cls: type[Metadata], value: dict[str, t.Any]) -> Metadata:
         )
 
     def to_dict(self) -> dict[str, t.Any]:
-        """Convert metadata to a JSON-encodeable dictionary.
+        """Convert metadata to a JSON-encodable dictionary.
 
         Returns:
             Metadata object.
diff --git a/singer_sdk/authenticators.py b/singer_sdk/authenticators.py
index 61382daba..970c777ad 100644
--- a/singer_sdk/authenticators.py
+++ b/singer_sdk/authenticators.py
@@ -462,9 +462,7 @@ def client_id(self) -> str | None:
         Returns:
             Optional client secret from stream config if it has been set.
         """
-        if self.config:
-            return self.config.get("client_id")
-        return None
+        return self.config.get("client_id") if self.config else None
 
     @property
     def client_secret(self) -> str | None:
@@ -473,9 +471,7 @@ def client_secret(self) -> str | None:
         Returns:
             Optional client secret from stream config if it has been set.
         """
-        if self.config:
-            return self.config.get("client_secret")
-        return None
+        return self.config.get("client_secret") if self.config else None
 
     def is_token_valid(self) -> bool:
         """Check if token is valid.
@@ -487,9 +483,7 @@ def is_token_valid(self) -> bool:
             return False
         if not self.expires_in:
             return True
-        if self.expires_in > (utc_now() - self.last_refreshed).total_seconds():
-            return True
-        return False
+        return self.expires_in > (utc_now() - self.last_refreshed).total_seconds()
 
     # Authentication and refresh
     def update_access_token(self) -> None:
@@ -520,7 +514,7 @@ def update_access_token(self) -> None:
         self.expires_in = int(expiration) if expiration else None
         if self.expires_in is None:
             self.logger.debug(
-                "No expires_in receied in OAuth response and no "
+                "No expires_in received in OAuth response and no "
                 "default_expiration set. Token will be treated as if it never "
                 "expires.",
             )
@@ -566,7 +560,7 @@ def oauth_request_body(self) -> dict:
 
     @property
     def oauth_request_payload(self) -> dict:
-        """Return request paytload for OAuth request.
+        """Return request payload for OAuth request.
 
         Returns:
             Payload object for OAuth.
diff --git a/singer_sdk/connectors/sql.py b/singer_sdk/connectors/sql.py
index c6f957589..6b0552a22 100644
--- a/singer_sdk/connectors/sql.py
+++ b/singer_sdk/connectors/sql.py
@@ -902,9 +902,6 @@ def merge_sql_types(
                 if issubclass(
                     generic_type,
                     (sqlalchemy.types.String, sqlalchemy.types.Unicode),
-                ) or issubclass(
-                    generic_type,
-                    (sqlalchemy.types.String, sqlalchemy.types.Unicode),
                 ):
                     # If length None or 0 then is varchar max ?
                     if (
@@ -913,8 +910,6 @@ def merge_sql_types(
                         or (cur_len and (opt_len >= cur_len))
                     ):
                         return opt
-                # If best conversion class is equal to current type
-                # return the best conversion class
                 elif str(opt) == str(current_type):
                     return opt
 
diff --git a/singer_sdk/helpers/_conformers.py b/singer_sdk/helpers/_conformers.py
index 46963284e..0ca70e85c 100644
--- a/singer_sdk/helpers/_conformers.py
+++ b/singer_sdk/helpers/_conformers.py
@@ -16,11 +16,13 @@ def snakecase(string: str) -> str:
     """
     string = re.sub(r"[\-\.\s]", "_", string)
     string = (
-        string[0].lower()
-        + re.sub(
-            r"[A-Z]",
-            lambda matched: "_" + str(matched.group(0).lower()),
-            string[1:],
+        (
+            string[0].lower()
+            + re.sub(
+                r"[A-Z]",
+                lambda matched: f"_{matched.group(0).lower()!s}",
+                string[1:],
+            )
         )
         if string
         else string
diff --git a/singer_sdk/helpers/_flattening.py b/singer_sdk/helpers/_flattening.py
index c0abcb6b2..eeb244277 100644
--- a/singer_sdk/helpers/_flattening.py
+++ b/singer_sdk/helpers/_flattening.py
@@ -465,12 +465,9 @@ def _should_jsondump_value(key: str, value: t.Any, flattened_schema=None) -> boo
     if isinstance(value, (dict, list)):
         return True
 
-    if (
+    return bool(
         flattened_schema
         and key in flattened_schema
         and "type" in flattened_schema[key]
         and set(flattened_schema[key]["type"]) == {"null", "object", "array"}
-    ):
-        return True
-
-    return False
+    )
diff --git a/singer_sdk/helpers/_state.py b/singer_sdk/helpers/_state.py
index 9d0102186..a42a38433 100644
--- a/singer_sdk/helpers/_state.py
+++ b/singer_sdk/helpers/_state.py
@@ -18,7 +18,7 @@
 STARTING_MARKER = "starting_replication_value"
 
 
-def get_state_if_exists(  # noqa: PLR0911
+def get_state_if_exists(
     tap_state: dict,
     tap_stream_id: str,
     state_partition_context: dict | None = None,
@@ -47,9 +47,7 @@ def get_state_if_exists(  # noqa: PLR0911
 
     stream_state = tap_state["bookmarks"][tap_stream_id]
     if not state_partition_context:
-        if key:
-            return stream_state.get(key, None)
-        return stream_state
+        return stream_state.get(key, None) if key else stream_state
     if "partitions" not in stream_state:
         return None  # No partitions defined
 
@@ -59,9 +57,7 @@ def get_state_if_exists(  # noqa: PLR0911
     )
     if matched_partition is None:
         return None  # Partition definition not present
-    if key:
-        return matched_partition.get(key, None)
-    return matched_partition
+    return matched_partition.get(key, None) if key else matched_partition
 
 
 def get_state_partitions_list(tap_state: dict, tap_stream_id: str) -> list[dict] | None:
@@ -84,10 +80,7 @@ def _find_in_partitions_list(
             f"{{state_partition_context}}.\nMatching state values were: {found!s}"
         )
         raise ValueError(msg)
-    if found:
-        return t.cast(dict, found[0])
-
-    return None
+    return t.cast(dict, found[0]) if found else None
 
 
 def _create_in_partitions_list(
diff --git a/singer_sdk/helpers/_typing.py b/singer_sdk/helpers/_typing.py
index 6eb7b3879..3a87ab4b9 100644
--- a/singer_sdk/helpers/_typing.py
+++ b/singer_sdk/helpers/_typing.py
@@ -79,7 +79,7 @@ def is_secret_type(type_dict: dict) -> bool:
     """Return True if JSON Schema type definition appears to be a secret.
 
     Will return true if either `writeOnly` or `secret` are true on this type
-    or any of the type's subproperties.
+    or any of the type's sub-properties.
 
     Args:
         type_dict: The JSON Schema type to check.
@@ -96,7 +96,7 @@ def is_secret_type(type_dict: dict) -> bool:
         return True
 
     if "properties" in type_dict:
-        # Recursively check subproperties and return True if any child is secret.
+        # Recursively check sub-properties and return True if any child is secret.
         return any(
             is_secret_type(child_type_dict)
             for child_type_dict in type_dict["properties"].values()
@@ -388,6 +388,7 @@ def conform_record_data_types(
     return rec
 
 
+# TODO: This is in dire need of refactoring. It's a mess.
 def _conform_record_data_types(  # noqa: PLR0912
     input_object: dict[str, t.Any],
     schema: dict,
@@ -405,7 +406,7 @@ def _conform_record_data_types(  # noqa: PLR0912
         input_object: A single record
         schema: JSON schema the given input_object is expected to meet
         level:  Specifies how recursive the conformance process should be
-        parent: '.' seperated path to this element from the object root (for logging)
+        parent: '.' separated path to this element from the object root (for logging)
     """
     output_object: dict[str, t.Any] = {}
     unmapped_properties: list[str] = []
diff --git a/singer_sdk/io_base.py b/singer_sdk/io_base.py
index 07da6e63e..d389bfd08 100644
--- a/singer_sdk/io_base.py
+++ b/singer_sdk/io_base.py
@@ -48,7 +48,7 @@ def _assert_line_requires(line_dict: dict, requires: set[str]) -> None:
         if not requires.issubset(line_dict):
             missing = requires - set(line_dict)
             msg = f"Line is missing required {', '.join(missing)} key(s): {line_dict}"
-            raise Exception(msg)
+            raise Exception(msg)  # TODO: Raise a more specific exception
 
     def deserialize_json(self, line: str) -> dict:
         """Deserialize a line of json.
diff --git a/singer_sdk/mapper.py b/singer_sdk/mapper.py
index 5b19f0b07..b48c49727 100644
--- a/singer_sdk/mapper.py
+++ b/singer_sdk/mapper.py
@@ -273,10 +273,7 @@ def transform(self, record: dict) -> dict | None:
             The transformed record.
         """
         transformed_record = self._transform_fn(record)
-        if not transformed_record:
-            return None
-
-        return super().transform(transformed_record)
+        return super().transform(transformed_record) if transformed_record else None
 
     def get_filter_result(self, record: dict) -> bool:
         """Return True to include or False to exclude.
@@ -291,7 +288,7 @@ def get_filter_result(self, record: dict) -> bool:
 
     @property
     def functions(self) -> dict[str, t.Callable]:
-        """Get availabale transformation functions.
+        """Get available transformation functions.
 
         Returns:
             Functions which should be available for expression evaluation.
diff --git a/singer_sdk/metrics.py b/singer_sdk/metrics.py
index 89d51a338..e4191eadf 100644
--- a/singer_sdk/metrics.py
+++ b/singer_sdk/metrics.py
@@ -263,10 +263,9 @@ def __exit__(
             exc_tb: The exception traceback.
         """
         if Tag.STATUS not in self.tags:
-            if exc_type is None:
-                self.tags[Tag.STATUS] = Status.SUCCEEDED
-            else:
-                self.tags[Tag.STATUS] = Status.FAILED
+            self.tags[Tag.STATUS] = (
+                Status.SUCCEEDED if exc_type is None else Status.FAILED
+            )
         log(self.logger, Point("timer", self.metric, self.elapsed(), self.tags))
 
     def elapsed(self) -> float:
diff --git a/singer_sdk/sinks/core.py b/singer_sdk/sinks/core.py
index ec4664f67..e56d5aab5 100644
--- a/singer_sdk/sinks/core.py
+++ b/singer_sdk/sinks/core.py
@@ -247,7 +247,7 @@ def _add_sdc_metadata_to_record(
             tz=datetime.timezone.utc,
         ).isoformat()
         record["_sdc_batched_at"] = (
-            context.get("batch_start_time", None)
+            context.get("batch_start_time")
             or datetime.datetime.now(tz=datetime.timezone.utc)
         ).isoformat()
         record["_sdc_deleted_at"] = record.get("_sdc_deleted_at")
diff --git a/singer_sdk/sinks/sql.py b/singer_sdk/sinks/sql.py
index 238e83dec..5c143818c 100644
--- a/singer_sdk/sinks/sql.py
+++ b/singer_sdk/sinks/sql.py
@@ -98,13 +98,7 @@ def schema_name(self) -> str | None:
         if default_target_schema:
             return default_target_schema
 
-        if len(parts) in {2, 3}:
-            # Stream name is a two-part or three-part identifier.
-            # Use the second-to-last part as the schema name.
-            return self.conform_name(parts[-2], "schema")
-
-        # Schema name not detected.
-        return None
+        return self.conform_name(parts[-2], "schema") if len(parts) in {2, 3} else None
 
     @property
     def database_name(self) -> str | None:
diff --git a/singer_sdk/tap_base.py b/singer_sdk/tap_base.py
index d4b5a8dc3..f7a31e73c 100644
--- a/singer_sdk/tap_base.py
+++ b/singer_sdk/tap_base.py
@@ -121,10 +121,10 @@ def streams(self) -> dict[str, Stream]:
         Returns:
             A mapping of names to streams, using discovery or a provided catalog.
         """
-        input_catalog = self.input_catalog
-
         if self._streams is None:
             self._streams = {}
+            input_catalog = self.input_catalog
+
             for stream in self.load_streams():
                 if input_catalog is not None:
                     stream.apply_catalog(input_catalog)
diff --git a/singer_sdk/target_base.py b/singer_sdk/target_base.py
index aabd8a640..c9d5d62ef 100644
--- a/singer_sdk/target_base.py
+++ b/singer_sdk/target_base.py
@@ -370,7 +370,7 @@ def _process_schema_message(self, message_dict: dict) -> None:
 
         stream_name = message_dict["stream"]
         schema = message_dict["schema"]
-        key_properties = message_dict.get("key_properties", None)
+        key_properties = message_dict.get("key_properties")
         do_registration = False
         if stream_name not in self.mapper.stream_maps:
             do_registration = True
diff --git a/singer_sdk/testing/factory.py b/singer_sdk/testing/factory.py
index ce6d2ec4c..f31930017 100644
--- a/singer_sdk/testing/factory.py
+++ b/singer_sdk/testing/factory.py
@@ -144,6 +144,7 @@ def runner(self) -> TapTestRunner | TargetTestRunner:
 
         return TapTestClass
 
+    # TODO: Refactor this. It's too long and nested.
     def _annotate_test_class(  # noqa: C901
         self,
         empty_test_class: type[BaseTestClass],
diff --git a/singer_sdk/testing/legacy.py b/singer_sdk/testing/legacy.py
index 5baa94034..5329b3224 100644
--- a/singer_sdk/testing/legacy.py
+++ b/singer_sdk/testing/legacy.py
@@ -150,10 +150,7 @@ def _get_tap_catalog(
     # Test discovery
     tap.run_discovery()
     catalog_dict = tap.catalog_dict
-    if select_all:
-        return _select_all(catalog_dict)
-
-    return catalog_dict
+    return _select_all(catalog_dict) if select_all else catalog_dict
 
 
 def _select_all(catalog_dict: dict) -> dict:
diff --git a/singer_sdk/typing.py b/singer_sdk/typing.py
index a9c48303e..37c1f40c1 100644
--- a/singer_sdk/typing.py
+++ b/singer_sdk/typing.py
@@ -965,12 +965,14 @@ def to_jsonschema_type(
         msg = "Expected `str` or a SQLAlchemy `TypeEngine` object or type."
         raise ValueError(msg)
 
-    # Look for the type name within the known SQL type names:
-    for sqltype, jsonschema_type in sqltype_lookup.items():
-        if sqltype.lower() in type_name.lower():
-            return jsonschema_type
-
-    return sqltype_lookup["string"]  # safe failover to str
+    return next(
+        (
+            jsonschema_type
+            for sqltype, jsonschema_type in sqltype_lookup.items()
+            if sqltype.lower() in type_name.lower()
+        ),
+        sqltype_lookup["string"],  # safe failover to str
+    )
 
 
 def _jsonschema_type_check(jsonschema_type: dict, type_check: tuple[str]) -> bool:
@@ -981,7 +983,7 @@ def _jsonschema_type_check(jsonschema_type: dict, type_check: tuple[str]) -> boo
         type_check: A tuple of type strings to look for.
 
     Returns:
-        True if the schema suports the type.
+        True if the schema supports the type.
     """
     if "type" in jsonschema_type:
         if isinstance(jsonschema_type["type"], (list, tuple)):
@@ -991,12 +993,9 @@ def _jsonschema_type_check(jsonschema_type: dict, type_check: tuple[str]) -> boo
         elif jsonschema_type.get("type") in type_check:
             return True
 
-    if any(
+    return any(
         _jsonschema_type_check(t, type_check) for t in jsonschema_type.get("anyOf", ())
-    ):
-        return True
-
-    return False
+    )
 
 
 def to_sql_type(  # noqa: PLR0911, C901