chore: replace mypy with ty for type checking

.github/workflows/type-check.yml

@@ -0,0 +1,33 @@
+---
+name: Type check
+on:  # yamllint disable-line rule:truthy
+  workflow_dispatch:
+  push:
+    branches:
+      - master
+      - v*
+  pull_request:
+    branches:
+      - master
+      - v*
+
+# ty runs here rather than on pre-commit.ci, which blocks the network access ty
+# needs to resolve this project's dependencies.
+jobs:
+  ty:
+    name: ty
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+
+      - uses: actions/checkout@v7
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v9
+        with:
+          enable-cache: true
+          python-version: '3.11'
+
+      - name: Run ty
+        run: uv run --frozen ty check

.gitignore

@@ -90,9 +90,6 @@ target/
 # vscode
 .vscode/
 
-# Mypy cache
-.mypy_cache/
-
 # Environments
 *.env
 .venv

.pre-commit-config.yaml

@@ -1,5 +1,11 @@
 default_language_version:
   python: python3.11
+ci:
+  # The ty hook shells out to uv to resolve this project's dependencies, and
+  # pre-commit.ci runs hooks without network access. The Type check workflow
+  # runs ty in GitHub Actions instead.
+  skip:
+    - ty
 repos:
   - repo: 'https://github.com/pre-commit/pre-commit-hooks'
     rev: v6.0.0
@@ -45,22 +51,19 @@ repos:
         args:
           - '--check'
           - '--diff'
-  - repo: 'https://github.com/pre-commit/mirrors-mypy'
-    rev: v2.1.0
+  # Runs the ty pinned in pyproject.toml, the same command the Type check
+  # workflow runs, so the version is declared in exactly one place. The hook
+  # takes no file arguments: an edit in one file can move diagnostics into
+  # another, so ty rechecks its whole configured scope every run.
+  - repo: local
     hooks:
-      - id: mypy
-        args:
-          - '--show-error-codes'
-          - '--ignore-missing-imports'
-          - '--explicit-package-bases'
-        files: '^dbt/adapters'
-      - id: mypy
-        alias: mypy-check
-        stages:
-          - manual
-        args:
-          - '--show-error-codes'
-          - '--pretty'
-          - '--ignore-missing-imports'
-          - '--explicit-package-bases'
-        files: '^dbt/adapters'
+      - id: ty
+        name: ty
+        entry: uv run --frozen ty check
+        language: system
+        types_or:
+          - python
+          - pyi
+        pass_filenames: false
+        always_run: true
+        require_serial: true

CHANGELOG.md

@@ -14,6 +14,10 @@
 
 - Fix `dbt_sqlserver_use_dbt_transactions: True` (now the default) breaking two things that assumed the old autocommit-per-statement behavior: building an index with `build_options: {online: true}` or `{resumable: true}` on a fresh table or `table_refresh_method`'s rename-swap path (SQL Server rejects `RESUMABLE` inside a user transaction outright — `create_indexes` didn't split these out the way index reconciliation already did); and the `dbt_full_refresh_incomplete` crash marker on `full_refresh_build=prebuilt` and incremental full refreshes, which previously rode the same ambient transaction as the rebuild it's meant to survive, so a real failure mid-rebuild rolled the marker back along with everything else instead of leaving it in place to block the next normal run.
 
+#### Under the hood
+
+- Replace mypy with [`ty`](https://docs.astral.sh/ty/) for type checking, completing the move to a single Astral toolchain (Ruff for lint and format, `ty` for types). Same scope as before (`dbt/adapters`, unresolvable `dbt.*` imports ignored), configured in `pyproject.toml`. `ty` runs in a new Type check workflow rather than on pre-commit.ci, which blocks the network access it needs. [#712](https://github.com/dbt-msft/dbt-sqlserver/issues/712)
+
 ### v1.11.0
 
 #### Features

Makefile

@@ -6,10 +6,10 @@ dev: ## Installs adapter in develop mode along with development dependencies
 	@\
 	uv sync --all-extras && uv run pre-commit install
 
-.PHONY: mypy
-mypy: ## Runs mypy against staged changes for static type checking.
+.PHONY: ty
+ty: ## Runs ty over the adapter package for static type checking.
 	@\
-	uv run pre-commit run --hook-stage manual mypy-check
+	uv run pre-commit run --hook-stage manual ty
 
 .PHONY: ruff
 ruff: ## Runs ruff against staged changes to enforce style guide.
@@ -22,10 +22,10 @@ format: ## Runs ruff format against staged changes to enforce style guide.
 	uv run pre-commit run --hook-stage manual ruff-format-check -v
 
 .PHONY: lint
-lint: ## Runs ruff and mypy code checks against staged changes.
+lint: ## Runs ruff and ty code checks against staged changes.
 	@status=0; \
 	uv run pre-commit run ruff-check-manual --hook-stage manual || status=1; \
-	uv run pre-commit run mypy-check --hook-stage manual || status=1; \
+	uv run pre-commit run ty --hook-stage manual || status=1; \
 	exit $$status
 
 .PHONY: all
@@ -49,7 +49,7 @@ test: ## Runs unit tests and code checks against staged changes.
 	uv run pytest -n auto -ra -v tests/unit || status=1; \
 	uv run pre-commit run ruff-format-check --hook-stage manual || status=1; \
 	uv run pre-commit run ruff-check-manual --hook-stage manual || status=1; \
-	uv run pre-commit run mypy-check --hook-stage manual || status=1; \
+	uv run pre-commit run ty --hook-stage manual || status=1; \
 	exit $$status
 
 .PHONY: server

dbt/adapters/sqlserver/relation_configs/index.py

@@ -593,13 +593,19 @@ def index_config_changes(
             SQLServerIndexConfig.parse_relation_results(rows_by_name[name])
         )
         changes.append(
-            SQLServerIndexConfigChange(action=RelationConfigChangeAction.drop, context=context)
+            SQLServerIndexConfigChange(
+                # `action` is inherited from RelationConfigChange, a dataclass a
+                # type checker cannot see; see [tool.ty.rules] in pyproject.toml.
+                action=RelationConfigChangeAction.drop,  # ty: ignore[unknown-argument]
+                context=context,
+            )
         )
     for name, config in expected_by_name.items():
         if name not in existing_names:
             changes.append(
                 SQLServerIndexConfigChange(
-                    action=RelationConfigChangeAction.create, context=config
+                    action=RelationConfigChangeAction.create,  # ty: ignore[unknown-argument]
+                    context=config,
                 )
             )
     return changes, warnings

dbt/adapters/sqlserver/sqlserver_adapter.py

@@ -1,5 +1,5 @@
 import datetime as _dt
-from typing import Any, Dict, List, Optional, Tuple, Union
+from typing import Any, Dict, List, Optional, Tuple, Type, Union
 
 import agate
 import dbt_common.exceptions
@@ -82,7 +82,8 @@ class SQLServerAdapter(SQLAdapter):
     """
 
     ConnectionManager = SQLServerConnectionManager
-    Column = SQLServerColumn
+    # Annotated because __init__ swaps in the SQLServerColumnNative subclass.
+    Column: Type[SQLServerColumn] = SQLServerColumn
     AdapterSpecificConfigs = SQLServerConfigs
     Relation = SQLServerRelation
 
@@ -115,8 +116,12 @@ def __init__(self, config, mp_context=None):
 
     @property
     def _behavior_flags(self) -> List[BehaviorFlag]:
-        return [
-            {
+        # dbt-common declares BehaviorFlag's optional keys with a NotRequired
+        # that falls back to Optional under a try/except ImportError shim, so a
+        # type checker reads `source` and `docs_url` as required and rejects
+        # every flag below. The suppressions go stale once that shim is dropped.
+        return [  # ty: ignore[invalid-return-type]
+            {  # ty: ignore[missing-typed-dict-key]
                 "name": "dbt_sqlserver_use_default_schema_concat",
                 "default": False,
                 "description": (
@@ -128,7 +133,7 @@ def _behavior_flags(self) -> List[BehaviorFlag]:
                     "macro in your project instead."
                 ),
             },
-            {
+            {  # ty: ignore[missing-typed-dict-key]
                 "name": "dbt_sqlserver_disable_empty_relation_aliases",
                 "default": True,
                 "description": (
@@ -137,7 +142,7 @@ def _behavior_flags(self) -> List[BehaviorFlag]:
                     "out of alias generation temporarily for testing."
                 ),
             },
-            {
+            {  # ty: ignore[missing-typed-dict-key]
                 "name": "dbt_sqlserver_use_native_string_types",
                 "default": True,
                 "description": (
@@ -149,7 +154,7 @@ def _behavior_flags(self) -> List[BehaviorFlag]:
                     "and will be removed in a future release."
                 ),
             },
-            {
+            {  # ty: ignore[missing-typed-dict-key]
                 "name": "dbt_sqlserver_enable_safe_type_expansion",
                 "default": False,
                 "description": (
@@ -159,7 +164,7 @@ def _behavior_flags(self) -> List[BehaviorFlag]:
                     "and numeric(p,s) -> numeric(p2,s2) using alter column."
                 ),
             },
-            {
+            {  # ty: ignore[missing-typed-dict-key]
                 "name": "dbt_sqlserver_use_dbt_transactions",
                 "default": True,
                 "description": (

dbt/adapters/sqlserver/sqlserver_relation.py

@@ -15,7 +15,7 @@
 
 @dataclass(frozen=True, eq=False, repr=False)
 class SQLServerRelation(BaseRelation):
-    type: Optional[SQLServerRelationType] = None  # type: ignore
+    type: Optional[SQLServerRelationType] = None
     include_policy: SQLServerIncludePolicy = field(
         default_factory=lambda: SQLServerIncludePolicy()
     )

pyproject.toml

@@ -66,7 +66,6 @@ dev = [
     "flaky",
     "freezegun>=1.5.0,<2.0",
     "ipdb",
-    "mypy==2.1.0",
     "pre-commit",
     "pytest",
     "pytest-cov",
@@ -77,6 +76,9 @@ dev = [
     "ruff",
     "tox>=3.13",
     "twine",
+    # Pinned exactly: this is the single source of the ty version, read by the
+    # pre-commit hook, `make ty` and the Type check workflow alike.
+    "ty==0.0.64",
 ]
 
 [project.urls]
@@ -119,4 +121,18 @@ known-first-party = ["dbt"]
 ban-relative-imports = "all"
 
 [tool.ty.environment]
-python = ".venv"
+# Check against the oldest interpreter the adapter is built for, matching
+# ruff's target-version, rather than whichever version .venv happens to hold.
+python-version = "3.11"
+
+[tool.ty.src]
+# The adapter package only; the test suite is not type checked.
+include = ["dbt/adapters"]
+
+[tool.ty.rules]
+# `dbt` is a namespace split across distributions: dbt-core and dbt-adapters
+# own `dbt/` and `dbt/adapters/` in site-packages, this repo contributes
+# `dbt/adapters/sqlserver` from the project root, and the two halves are joined
+# at runtime by the editable install's import hook. No static checker can
+# follow that, so every `dbt.*` import reads as unresolvable here.
+unresolved-import = "ignore"