feat(sqlserver): add NEXT VALUE FOR and MERGE OUTPUT/HOLDLOCK, wire protocol stubs

Author: vistart

src/rhosocial/activerecord/backend/impl/sqlserver/__init__.py

@@ -30,6 +30,7 @@
     SQLServerSystemVersioningClause,
     SQLServerOpenJsonExpression,
     OpenJsonColumn,
+    SQLServerNextValueForExpression,
     SQLServerTryCastExpression,
     SQLServerTryConvertExpression,
     SQLServerContainsPredicate,
@@ -88,6 +89,7 @@
     "SQLServerSystemVersioningClause",
     "SQLServerOpenJsonExpression",
     "OpenJsonColumn",
+    "SQLServerNextValueForExpression",
     "SQLServerTryCastExpression",
     "SQLServerTryConvertExpression",
     "SQLServerContainsPredicate",

src/rhosocial/activerecord/backend/impl/sqlserver/dialect.py

@@ -53,6 +53,11 @@
     SQLServerPaginationSupport,
     SQLServerMergeSupport,
     SQLServerPartitionSupport,
+    SQLServerOutputSupport,
+    SQLServerTableHintSupport,
+    SQLServerTryCastSupport,
+    SQLServerIdentitySupport,
+    SQLServerIndexedViewSupport,
 )
 from rhosocial.activerecord.backend.dialect.mixins import (
     CollationMixin,
@@ -96,6 +101,8 @@
 from rhosocial.activerecord.backend.dialect.exceptions import UnsupportedFeatureError
 from .collation import validate_sqlserver_collation_name
 from .alter_table_modifier import SQLServerAlterColumnModifierMixin
+from .mixins.sequence import SQLServerSequenceMixin
+from .mixins.protocol_support import SQLServerProtocolSupportMixin
 # SQLServerPartitionMixin is registered lazily in _register_partition_formatters()
 
 if TYPE_CHECKING:
@@ -169,6 +176,8 @@ class SQLServerDialect(
     DQLMixin,
     DMLMixin,
     SQLServerAlterColumnModifierMixin,  # Before DDLColumnMixin to override format_*_action
+    SQLServerProtocolSupportMixin,  # SQL Server protocol contract implementations
+    SQLServerSequenceMixin,  # NEXT VALUE FOR formatter (2012+)
     DDLColumnMixin,
     DDLTypeMixin,
     # Feature mixins
@@ -203,12 +212,14 @@ class SQLServerDialect(
     CTESupport,
     FilterClauseSupport,
     WindowFunctionSupport,
+    SQLServerJSONSupport,  # Before JSONSupport (subclass must precede its base)
     JSONSupport,
     ReturningSupport,
     AdvancedGroupingSupport,
     ArraySupport,
     ExplainSupport,
     GraphSupport,
+    SQLServerLockingSupport,  # Before LockingSupport
     LockingSupport,
     MergeSupport,
     OrderedSetAggregationSupport,
@@ -224,15 +235,25 @@ class SQLServerDialect(
     SchemaSupport,
     IndexSupport,
     SequenceSupport,
+    SQLServerTableSupport,  # Before TableSupport
     TableSupport,
     ConstraintSupport,
     IntrospectionSupport,
     TransactionControlSupport,
     SQLFunctionSupport,
-    # SQL Server-specific protocols (removed from MRO to avoid diamond inheritance)
-    # SQLServerTableSupport, SQLServerLockingSupport, SQLServerJSONSupport,
-    # SQLServerTemporalTableSupport, SQLServerSequenceSupport,
-    #     SQLServerFullTextSearchSupport, SQLServerPaginationSupport, SQLServerMergeSupport,
+    # SQL Server-specific protocols (marker classes for isinstance() checks;
+    # implementations live in SQLServerProtocolSupportMixin / SQLServerSequenceMixin)
+    SQLServerOutputSupport,
+    SQLServerPaginationSupport,
+    SQLServerFullTextSearchSupport,
+    SQLServerTryCastSupport,
+    SQLServerTableHintSupport,
+    SQLServerTemporalTableSupport,
+    SQLServerMergeSupport,
+    SQLServerSequenceSupport,
+    SQLServerIdentitySupport,
+    SQLServerIndexedViewSupport,
+    SQLServerPartitionSupport,  # Before PartitionSupport
     PartitionSupport,
 ):
     """
@@ -1434,12 +1455,20 @@ def format_merge_statement(self, expr: "MergeExpression") -> Tuple[str, tuple]:
         on_sql, on_params = expr.on_condition.to_sql()
         all_params.extend(on_params)
 
+        dialect_options = getattr(expr, "dialect_options", {}) or {}
+        output_columns = dialect_options.get("output")
+        output_action = dialect_options.get("output_action", False)
+        holdlock = dialect_options.get("holdlock", False)
+
         parts = [
             f"MERGE INTO {target_sql}",
             f"USING {source_sql}",
             f"ON {on_sql}",
         ]
 
+        if holdlock and self.supports_merge_holdlock():
+            parts[0] = f"MERGE INTO {target_sql} WITH (HOLDLOCK)"
+
         for action in expr.when_matched:
             action_parts = []
             if action.condition:
@@ -1484,6 +1513,14 @@ def format_merge_statement(self, expr: "MergeExpression") -> Tuple[str, tuple]:
                     action_parts.append("THEN INSERT DEFAULT VALUES")
             parts.append(" ".join(action_parts))
 
+        if output_columns and self.supports_merge_output():
+            action_type = "$action" if output_action else None
+            output_sql, output_params = self.format_merge_output_clause(
+                list(output_columns), action_type=action_type
+            )
+            parts.append(output_sql)
+            all_params.extend(output_params)
+
         return " ".join(parts), tuple(all_params)
 
     def format_set_transaction(self, expr: "SetTransactionExpression") -> Tuple[str, tuple]:

src/rhosocial/activerecord/backend/impl/sqlserver/expression/__init__.py

@@ -5,6 +5,7 @@
 from .locking import SQLServerTableHintClause, SQLServerTableHint, SQLServerReadPastHint
 from .temporal import SQLServerTemporalPeriodDefinition, SQLServerSystemVersioningClause
 from .openjson import SQLServerOpenJsonExpression, OpenJsonColumn
+from .sequence import SQLServerNextValueForExpression
 from .functions import (
     SQLServerTryCastExpression,
     SQLServerTryConvertExpression,
@@ -22,8 +23,9 @@
     "SQLServerSystemVersioningClause",
     "SQLServerOpenJsonExpression",
     "OpenJsonColumn",
+    "SQLServerNextValueForExpression",
     "SQLServerTryCastExpression",
     "SQLServerTryConvertExpression",
     "SQLServerContainsPredicate",
     "SQLServerFreetextPredicate",
-]
+]

src/rhosocial/activerecord/backend/impl/sqlserver/expression/sequence.py

@@ -0,0 +1,48 @@
+# src/rhosocial/activerecord/backend/impl/sqlserver/expression/sequence.py
+"""SQL Server SEQUENCE value expression.
+
+SQL Server sequences are objects that generate a sequence of numeric values.
+Values are obtained with the ``NEXT VALUE FOR`` expression (SQL Server 2012+):
+
+    SELECT NEXT VALUE FOR my_seq;
+    INSERT INTO t (id) VALUES (NEXT VALUE FOR my_seq);
+
+This module defines the expression used to request the next value from a
+sequence. SQL generation is delegated to the dialect's
+``format_next_value_for`` formatter.
+"""
+
+from typing import TYPE_CHECKING
+
+from rhosocial.activerecord.backend.expression.bases import BaseExpression, SQLQueryAndParams
+
+if TYPE_CHECKING:
+    from ..dialect import SQLServerDialect
+
+
+class SQLServerNextValueForExpression(BaseExpression):
+    """SQL Server NEXT VALUE FOR expression (2012+).
+
+    Requests the next value from a sequence object.
+
+    Attributes:
+        sequence_name: Name of the sequence (may be schema-qualified).
+
+    Example:
+        >>> expr = SQLServerNextValueForExpression(dialect, "my_seq")
+        >>> sql, params = expr.to_sql()
+        >>> assert sql == "NEXT VALUE FOR [my_seq]"
+    """
+
+    def __init__(self, dialect: "SQLServerDialect", sequence_name: str):
+        super().__init__(dialect)
+        self.sequence_name = sequence_name
+
+    def validate(self, strict: bool = True) -> None:
+        if not strict:
+            return
+        if not isinstance(self.sequence_name, str):
+            raise TypeError(f"sequence_name must be str, got {type(self.sequence_name)}")
+
+    def to_sql(self) -> SQLQueryAndParams:
+        return self.dialect.format_next_value_for(self), ()

src/rhosocial/activerecord/backend/impl/sqlserver/mixins/__init__.py

@@ -3,10 +3,14 @@
 from .concurrency import SQLServerConcurrencyMixin
 from .backend_mixin import SQLServerBackendMixin
 from .partition import SQLServerPartitionMixin
+from .sequence import SQLServerSequenceMixin
+from .protocol_support import SQLServerProtocolSupportMixin
 
 __all__ = [
     "SQLServerTypeSupportMixin",
     "SQLServerConcurrencyMixin",
     "SQLServerBackendMixin",
     "SQLServerPartitionMixin",
-]
+    "SQLServerSequenceMixin",
+    "SQLServerProtocolSupportMixin",
+]

src/rhosocial/activerecord/backend/impl/sqlserver/mixins/backend_mixin.py

@@ -1,14 +1,12 @@
 # src/rhosocial/activerecord/backend/impl/sqlserver/mixins/backend_mixin.py
-import logging
-from typing import Any, Dict, Optional, Tuple, Type
+from typing import Any, Dict, Optional, Tuple, Type, TYPE_CHECKING
 
-from rhosocial.activerecord.backend.type_adapter import SQLTypeAdapter
-
-from ..dialect import SQLServerDialect
+if TYPE_CHECKING:
+    from ..dialect import SQLServerDialect
 
 
 class SQLServerBackendMixin:
-    _dialect: SQLServerDialect
+    _dialect: "SQLServerDialect"
     _connection: Optional[object]
 
     def set_nocount(self, on: bool = True) -> None:
@@ -225,7 +223,6 @@ def _handle_error(self, error: Exception) -> None:
             DeadlockError,
             IntegrityError,
             OperationalError,
-            QueryError,
         )
 
         error_msg = str(error)