fix: raise ConfigurationError from bootstrap() after teardown()

CONTEXT.md

@@ -14,7 +14,8 @@ project uses it.
 The user-facing entry point, one class per framework. It owns exactly one application for the life
 of the process; it is not a builder you can run twice. A second bootstrapper on the same application (or,
 for Litestar, the same `AppConfig`) warns at construction and raises `ConfigurationError` from
-`bootstrap()`.
+`bootstrap()`. Once torn down, a bootstrapper cannot bootstrap again: `bootstrap()` after
+`teardown()` raises `ConfigurationError`.
 
 **Instrument**:
 One observability or middleware concern: logging, tracing, metrics, profiling, CORS, Swagger, or
@@ -55,7 +56,7 @@ possible probe.
 
 **Free**:
 Without a web framework: `FreeBootstrapper`, `FreeConfig`, the `free-all` extra. It has no
-application, so nothing to attach teardown to and no double-bootstrap guard.
+application, so nothing to attach teardown to and no guard against a second bootstrapper.
 _Avoid_: bare "free" for PEP 703 free-threaded CPython, which this project also supports. Write
 "free-threaded" in full.
 

lite_bootstrap/bootstrappers/base.py

@@ -34,6 +34,7 @@ class BaseBootstrapper(abc.ABC, typing.Generic[ApplicationT]):
 
     def __init__(self, bootstrap_config: BaseConfig) -> None:
         self.is_bootstrapped = False
+        self._torn_down = False
         # Set when another bootstrapper already owns this application; bootstrap() then refuses.
         self._attach_skipped = False
         if not self.is_ready():
@@ -131,6 +132,13 @@ def bootstrap(self) -> ApplicationT:
                 f"{type(self).__name__} per application."
             )
             raise ConfigurationError(msg)
+        if self._torn_down:
+            msg = (
+                f"{type(self).__name__} was torn down and cannot bootstrap again: its instruments "
+                f"already changed the application. To bootstrap again, construct a new "
+                f"{type(self).__name__}, with a new application if it takes one."
+            )
+            raise ConfigurationError(msg)
         if self.is_bootstrapped:
             return self._application
         self.is_bootstrapped = True
@@ -143,6 +151,7 @@ def teardown(self) -> None:
         if not self.is_bootstrapped:
             return
         self.is_bootstrapped = False
+        self._torn_down = True
         with collect_teardown_errors(logger) as teardown_errors:
             for one_instrument in reversed(self.instruments):
                 with teardown_errors.capture(type(one_instrument).__name__):

tests/test_fastapi_bootstrap.py

@@ -214,6 +214,14 @@ def test_fastapi_config_inherits_otel_insecure_warning() -> None:
     assert matching, [str(w.message) for w in caught]
 
 
+def test_fastapi_bootstrap_after_teardown_raises() -> None:
+    bootstrapper = FastAPIBootstrapper(bootstrap_config=FastAPIConfig())
+    bootstrapper.bootstrap()
+    bootstrapper.teardown()
+    with pytest.raises(ConfigurationError, match="construct a new FastAPIBootstrapper"):
+        bootstrapper.bootstrap()
+
+
 def test_second_fastapi_bootstrapper_bootstrap_raises(fastapi_config: FastAPIConfig) -> None:
     application = fastapi.FastAPI()
     first = FastAPIBootstrapper(bootstrap_config=dataclasses.replace(fastapi_config, application=application))

tests/test_fastmcp_bootstrap.py

@@ -346,6 +346,14 @@ def test_fastmcp_bootstrap_without_structlog() -> None:
         bootstrapper.teardown()
 
 
+def test_fastmcp_bootstrap_after_teardown_raises() -> None:
+    bootstrapper = FastMcpBootstrapper(bootstrap_config=FastMcpConfig())
+    bootstrapper.bootstrap()
+    bootstrapper.teardown()
+    with pytest.raises(ConfigurationError, match="construct a new FastMcpBootstrapper"):
+        bootstrapper.bootstrap()
+
+
 def test_second_fastmcp_bootstrapper_bootstrap_raises() -> None:
     application = FastMCP()
     first = FastMcpBootstrapper(bootstrap_config=FastMcpConfig(application=application, service_name="a"))

tests/test_faststream_bootstrap.py

@@ -399,6 +399,14 @@ def _raise_on_write(_self: object, _value: object) -> None:
     structlog.get_logger("verify-reset")
 
 
+def test_faststream_bootstrap_after_teardown_raises() -> None:
+    bootstrapper = FastStreamBootstrapper(bootstrap_config=FastStreamConfig())
+    bootstrapper.bootstrap()
+    bootstrapper.teardown()
+    with pytest.raises(ConfigurationError, match="construct a new FastStreamBootstrapper"):
+        bootstrapper.bootstrap()
+
+
 def test_second_faststream_bootstrapper_bootstrap_raises(broker: RedisBroker) -> None:
     config_a = build_faststream_config(broker=broker)
     first = FastStreamBootstrapper(bootstrap_config=config_a)

tests/test_free_bootstrap.py

@@ -8,6 +8,7 @@
 from opentelemetry.sdk.trace import sampling
 
 from lite_bootstrap import (
+    ConfigurationError,
     FreeBootstrapper,
     FreeConfig,
     InstrumentDependencyMissingWarning,
@@ -35,6 +36,14 @@ def free_bootstrapper_config() -> FreeConfig:
     )
 
 
+def test_free_bootstrap_after_teardown_raises() -> None:
+    bootstrapper = FreeBootstrapper(bootstrap_config=FreeConfig())
+    bootstrapper.bootstrap()
+    bootstrapper.teardown()
+    with pytest.raises(ConfigurationError, match="construct a new FreeBootstrapper"):
+        bootstrapper.bootstrap()
+
+
 def test_free_bootstrap(free_bootstrapper_config: FreeConfig) -> None:
     bootstrapper = FreeBootstrapper(bootstrap_config=free_bootstrapper_config)
     bootstrapper.bootstrap()

tests/test_litestar_bootstrap.py

@@ -124,13 +124,12 @@ def test_litestar_bootstrap_twice_returns_the_same_application() -> None:
     assert bootstrapper.bootstrap() is bootstrapper.bootstrap()
 
 
-def test_litestar_bootstrap_after_teardown_builds_a_new_application() -> None:
-    bootstrapper = LitestarBootstrapper(
-        LitestarConfig(logging_enabled=False, health_checks_enabled=False, prometheus_metrics_path="")
-    )
-    first = bootstrapper.bootstrap()
+def test_litestar_bootstrap_after_teardown_raises() -> None:
+    bootstrapper = LitestarBootstrapper(bootstrap_config=LitestarConfig())
+    bootstrapper.bootstrap()
     bootstrapper.teardown()
-    assert bootstrapper.bootstrap() is not first
+    with pytest.raises(ConfigurationError, match="construct a new LitestarBootstrapper"):
+        bootstrapper.bootstrap()
 
 
 def test_litestar_bootstrapper_not_ready() -> None: