avoid Path interpreting . in deployment names as the beginning of…

… a file extension (#16553)

src/prefect/deployments/runner.py

@@ -41,6 +41,7 @@ def fast_flow():
     ConfigDict,
     Field,
     PrivateAttr,
+    field_validator,
     model_validator,
 )
 from rich.console import Console
@@ -220,6 +221,13 @@ class RunnerDeployment(BaseModel):
     def entrypoint_type(self) -> EntrypointType:
         return self._entrypoint_type
 
+    @field_validator("name", mode="before")
+    @classmethod
+    def validate_name(cls, value: str) -> str:
+        if value.endswith(".py"):
+            return Path(value).stem
+        return value
+
     @model_validator(mode="after")
     def validate_automation_names(self):
         """Ensure that each trigger has a name for its automation if none is provided."""
@@ -508,7 +516,7 @@ def from_flow(
             concurrency_options = None
 
         deployment = cls(
-            name=Path(name).stem,
+            name=name,
             flow_name=flow.name,
             schedules=constructed_schedules,
             concurrency_limit=concurrency_limit,

tests/runner/test_runner.py

@@ -1762,6 +1762,16 @@ async def test_init_runner_deployment_with_invalid_schedules(self):
                 ],
             )
 
+    async def test_deployment_name_with_dots(self):
+        # regression test for https://github.com/PrefectHQ/prefect/issues/16551
+        deployment = RunnerDeployment.from_flow(dummy_flow_1, name="..test-deployment")
+        assert deployment.name == "..test-deployment"
+
+        deployment2 = RunnerDeployment.from_flow(
+            dummy_flow_1, name="flow-from-my.python.module"
+        )
+        assert deployment2.name == "flow-from-my.python.module"
+
 
 class TestServer:
     async def test_healthcheck_fails_as_expected(self):