feat: add proper optional-dependencies for each modules (#75)

src/fastapi_toolsets/_imports.py

@@ -0,0 +1,9 @@
+"""Optional dependency helpers."""
+
+
+def require_extra(package: str, extra: str) -> None:
+    """Raise *ImportError* with an actionable install instruction."""
+    raise ImportError(
+        f"'{package}' is required to use this module. "
+        f"Install it with: pip install fastapi-toolsets[{extra}]"
+    )

src/fastapi_toolsets/cli/app.py

@@ -1,6 +1,11 @@
 """Main CLI application."""
 
-import typer
+try:
+    import typer
+except ImportError:
+    from .._imports import require_extra
+
+    require_extra(package="typer", extra="cli")
 
 from ..logger import configure_logging
 from .config import get_custom_cli

src/fastapi_toolsets/metrics/__init__.py

@@ -1,8 +1,19 @@
 """Prometheus metrics integration for FastAPI applications."""
 
-from .handler import init_metrics
+from typing import Any
+
 from .registry import Metric, MetricsRegistry
 
+try:
+    from .handler import init_metrics
+except ImportError:
+
+    def init_metrics(*_args: Any, **_kwargs: Any) -> None:
+        from .._imports import require_extra
+
+        require_extra(package="prometheus_client", extra="metrics")
+
+
 __all__ = [
     "Metric",
     "MetricsRegistry",

src/fastapi_toolsets/pytest/__init__.py

@@ -1,13 +1,24 @@
 """Pytest helpers for FastAPI testing: sessions, clients, and fixtures."""
 
-from .plugin import register_fixtures
-from .utils import (
-    cleanup_tables,
-    create_async_client,
-    create_db_session,
-    create_worker_database,
-    worker_database_url,
-)
+try:
+    from .plugin import register_fixtures
+except ImportError:
+    from .._imports import require_extra
+
+    require_extra(package="pytest", extra="pytest")
+
+try:
+    from .utils import (
+        cleanup_tables,
+        create_async_client,
+        create_db_session,
+        create_worker_database,
+        worker_database_url,
+    )
+except ImportError:
+    from .._imports import require_extra
+
+    require_extra(package="httpx", extra="pytest")
 
 __all__ = [
     "cleanup_tables",