feat(check): make check fails when a service imports another service's sdk at startup

README.md

@@ -2,7 +2,7 @@
 
 Copier template for a Python backend, either as a `backend/` part next to other parts or alone at the root of the project (`layout`): a uv project with one Docker image and one `python -m <module>` entrypoint per service (`api`, `bot`, `userbot`, `worker`, `scheduler`), pydantic-settings, rich logging, optional Dishka, MongoDB or PostgreSQL, Redis, taskiq (in-memory, Redis or PostgreSQL broker), CryptoPay, pydantic-ai and a DynamicConfig stored in the database.
 
-Ships `backend/docker-compose.yml` with root-relative paths and profiles per service, `docker-compose.override.yml.example` (published ports and the `caddy` network aliases, copied by `make env`), a `Makefile` with `fmt`, `check`, `build` and service-specific targets, `.env.example` and `CLAUDE.md`. Applied on top of the `infra` template, `layout: parts` or `layout: single` respectively.
+Ships `backend/docker-compose.yml` with root-relative paths and profiles per service, `docker-compose.override.yml.example` (published ports and the `caddy` network aliases, copied by `make env`), a `Makefile` with `fmt`, `check` (ruff, ty and `scripts/check_imports.py`, which keeps each service from importing the others' SDKs at startup), `build` and service-specific targets, `.env.example` and `CLAUDE.md`. Applied on top of the `infra` template, `layout: parts` or `layout: single` respectively.
 
 `DB__HOST`/`DB__PORT` and `REDIS__HOST`/`REDIS__PORT` say where the service really is. The bundled container takes the host as its network alias and listens on the port, the override publishes it on the machine. For an external database, point them at it and leave its profile out of `COMPOSE_PROFILES`.
 

template/{{ part_dir }}/Makefile.jinja

@@ -30,7 +30,8 @@ check:
 	uv run ruff format --check
 	uv run ruff check
 	uv run ty check
-{% if svc_modules %}
+{% if svc_modules %}	uv run python scripts/check_imports.py
+{% endif %}{% if svc_modules %}
 build:
 	$(COMPOSE) build {{ svc_modules[0] }}
 

template/{{ part_dir }}/scripts/{% if backend_services %}check_imports.py{% endif %}.jinja

@@ -0,0 +1,60 @@
+import os
+import subprocess
+import sys
+
+HEAVY = ["aiogram", "pyrogram", "fastapi", "google.genai"]
+SERVICES = {
+{%- if 'api' in backend_services %}
+    "api": (["api.app"], {"fastapi"}),
+{%- endif %}
+{%- if 'aiogram_bot' in backend_services %}
+    "bot": ({% if include_payments %}["bot"]{% else %}["bot.common", "bot.handlers"]{% endif %}, {"aiogram"}),
+{%- endif %}
+{%- if 'kurigram_userbot' in backend_services %}
+    "userbot": (["userbot.runner", "userbot.handlers"], {"pyrogram"}),
+{%- endif %}
+{%- if 'taskiq_worker' in backend_services %}
+    "worker": (["worker.broker", "worker.tasks"], {% if 'api' in backend_services %}{"fastapi"}{% else %}set(){% endif %}),
+{%- elif 'scheduler' in backend_services %}
+    "scheduler": (["scheduler"], set()),
+{%- endif %}
+}
+PROBE = """
+import importlib, sys
+for module in sys.argv[1].split(","):
+    importlib.import_module(module)
+print(" ".join(name for name in sys.argv[2:] if name in sys.modules))
+"""
+{%- if 'aiogram_bot' in backend_services %}
+ENV = {**os.environ, "BOT__TOKEN": "1:check"}
+{%- else %}
+ENV = dict(os.environ)
+{%- endif %}
+
+
+def loaded(modules: list[str]) -> tuple[set[str], str]:
+    result = subprocess.run(  # noqa: S603
+        [sys.executable, "-c", PROBE, ",".join(modules), *HEAVY],
+        capture_output=True,
+        text=True,
+        cwd="src",
+        env=ENV,
+        check=False,
+    )
+    error = (result.stderr.strip().splitlines() or ["exit code"])[-1]
+    return set(result.stdout.split()) & set(HEAVY), error if result.returncode else ""
+
+
+def main() -> int:
+    failed = False
+    for service, (modules, allowed) in SERVICES.items():
+        found, error = loaded(modules)
+        extra = sorted(found - allowed)
+        status = error or ("imports " + ", ".join(extra) if extra else "")
+        print(f"{service:10s} {'FAIL: ' + status if status else 'ok'}")
+        failed |= bool(status)
+    return int(failed)
+
+
+if __name__ == "__main__":
+    sys.exit(main())

template/{{ part_dir }}/{% if layout == 'part' %}CLAUDE.md{% endif %}

@@ -5,3 +5,9 @@ ruff format
 ruff check --fix
 ty check
 ```
+
+## Imports
+Every service imports only what it needs to start. `make check` runs `scripts/check_imports.py`, which fails when a service loads a heavy package it is not allowed; `SERVICES` there is the contract, extend it on purpose.
+- Package `__init__` files don't re-export clients or SDKs.
+- An SDK used by one function is imported inside it. On an async path load it first with `await preload("<module>")` from `utils.imports`, so the event loop never waits on the import.
+- Types used in Dishka provider signatures and `FromDishka[...]` stay real top-level imports.