feat: refactor storage submodule for improved readability and maintainability (#99)

Enhance the `storage` submodule by improving code structure and adding utility functions for path resolution and dependency checks. Update tests to ensure functionality remains intact.

Author: cofin

.gitignore

@@ -20,7 +20,8 @@ target/
 .claude/
 .cursor/
 .zed/
-
+.gemini
+.coverage*
 # files
 **/*.so
 **/*.sqlite

pyproject.toml

@@ -105,6 +105,7 @@ test = [
   "requests",
   "anyio",
   "coverage>=7.6.1",
+  "covdefaults",
   "pytest>=8.0.0",
   "pytest-asyncio>=0.23.8",
   "pytest-cov>=5.0.0",
@@ -168,6 +169,14 @@ include = [
   "sqlspec/utils/type_guards.py",         # Type guard utilities
   "sqlspec/utils/fixtures.py",            # File fixture loading
   "sqlspec/utils/data_transformation.py", # Data transformation utilities
+
+  # === STORAGE LAYER ===
+  "sqlspec/storage/_utils.py",
+  "sqlspec/storage/registry.py",
+  "sqlspec/storage/backends/base.py",
+  "sqlspec/storage/backends/obstore.py",
+  "sqlspec/storage/backends/fsspec.py",
+  "sqlspec/storage/backends/local.py",
 ]
 mypy-args = [
   "--ignore-missing-imports",

sqlspec/storage/_utils.py

@@ -0,0 +1,98 @@
+"""Shared utilities for storage backends."""
+
+from typing import TYPE_CHECKING
+
+from sqlspec.exceptions import MissingDependencyError
+from sqlspec.typing import PYARROW_INSTALLED
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+__all__ = ("ensure_pyarrow", "resolve_storage_path")
+
+
+def ensure_pyarrow() -> None:
+    """Ensure PyArrow is available for Arrow operations.
+
+    Raises:
+        MissingDependencyError: If pyarrow is not installed.
+    """
+    if not PYARROW_INSTALLED:
+        raise MissingDependencyError(package="pyarrow", install_package="pyarrow")
+
+
+def resolve_storage_path(
+    path: "str | Path", base_path: str = "", protocol: str = "file", strip_file_scheme: bool = True
+) -> str:
+    """Resolve path relative to base_path with protocol-specific handling.
+
+    Args:
+        path: Path to resolve (may include file:// scheme).
+        base_path: Base path to prepend if path is relative.
+        protocol: Storage protocol (file, s3, gs, etc.).
+        strip_file_scheme: Whether to strip file:// prefix.
+
+    Returns:
+        Resolved path string suitable for the storage backend.
+
+    Examples:
+        >>> resolve_storage_path("/data/file.txt", protocol="file")
+        'data/file.txt'
+
+        >>> resolve_storage_path(
+        ...     "file.txt", base_path="/base", protocol="file"
+        ... )
+        'base/file.txt'
+
+        >>> resolve_storage_path(
+        ...     "file:///data/file.txt", strip_file_scheme=True
+        ... )
+        'data/file.txt'
+
+        >>> resolve_storage_path(
+        ...     "/data/subdir/file.txt",
+        ...     base_path="/data",
+        ...     protocol="file",
+        ... )
+        'subdir/file.txt'
+    """
+    from pathlib import Path as PathlibPath
+
+    path_str = str(path)
+
+    if strip_file_scheme and path_str.startswith("file://"):
+        path_str = path_str.removeprefix("file://")
+
+    # For local file protocol
+    if protocol == "file":
+        path_obj = PathlibPath(path_str)
+
+        # Absolute path handling
+        if path_obj.is_absolute():
+            if base_path:
+                base_obj = PathlibPath(base_path)
+                # Try to make path relative to base_path
+                try:
+                    relative = path_obj.relative_to(base_obj)
+                    # Return joined path for FSSpec-style backends
+                    return f"{base_path.rstrip('/')}/{relative}"
+                except ValueError:
+                    # Path is outside base_path
+                    return path_str.lstrip("/")
+            # No base_path - strip leading /
+            return path_str.lstrip("/")
+
+        # Relative path with base_path - join them
+        if base_path:
+            return f"{base_path.rstrip('/')}/{path_str}"
+
+        # Relative path without base_path
+        return path_str
+
+    # For cloud storage protocols (s3, gs, etc.), join with base_path
+    if not base_path:
+        return path_str
+
+    clean_base = base_path.rstrip("/")
+    clean_path = path_str.lstrip("/")
+    return f"{clean_base}/{clean_path}"