Fix broken table_exists_at (Image.get_table doesn't return Nones any more) and add mypy + config.

Author: mildbyte

.gitignore

@@ -12,6 +12,7 @@ docs/_build/
 dist/
 .venv/
 .cache/
+.mypy_cache/
 
 .idea/
 pip-wheel-metadata

mypy.ini

@@ -0,0 +1,10 @@
+[mypy]
+python_version = 3.6
+warn_return_any = True
+warn_unused_configs = True
+
+# Ignore no stubs for modules like psycopg2 etc
+ignore_missing_imports = True
+
+# Allow reusing the same variable with multiple assignments of different types.
+allow_redefinition = True

pyproject.toml

@@ -38,6 +38,7 @@ pylint = "^2.4"
 black = { version = "*", allows-prereleases = true }
 pre-commit = "^1.18"
 httpretty = "^0.9.6"
+mypy = "^0.720"
 
 [tool.poetry.extras]
 ingestion = ["pandas", "sqlalchemy"]

splitgraph/core/repository.py

@@ -21,7 +21,7 @@
 from splitgraph.core.image_manager import ImageManager
 from splitgraph.core.sql import validate_import_sql
 from splitgraph.engine.postgres.engine import PostgresEngine
-from splitgraph.exceptions import CheckoutError, EngineInitializationError
+from splitgraph.exceptions import CheckoutError, EngineInitializationError, TableNotFoundError
 from ._common import (
     manage_audit_triggers,
     set_head,
@@ -1013,11 +1013,14 @@ def table_exists_at(
 ) -> bool:
     """Determines whether a given table exists in a Splitgraph image without checking it out. If `image_hash` is None,
     determines whether the table exists in the current staging area."""
-    return (
+    if image is None:
         repository.object_engine.table_exists(repository.to_schema(), table_name)
-        if image is None
-        else bool(image.get_table(table_name))
-    )
+    else:
+        try:
+            image.get_table(table_name)
+            return True
+        except TableNotFoundError:
+            return False
 
 
 def _sync(