From 89794fca6ab0cb7f4b6928479067a89413108eb9 Mon Sep 17 00:00:00 2001
From: Your Name <you@example.com>
Date: Mon, 12 Sep 2022 18:45:58 +0100
Subject: [PATCH] raise exception instead of asserting

---
 fastapi/routing.py | 15 ++++++---------
 tests/test_tags.py |  6 +++---
 2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/fastapi/routing.py b/fastapi/routing.py
index e8e5ba788..5899af62a 100644
--- a/fastapi/routing.py
+++ b/fastapi/routing.py
@@ -500,9 +500,8 @@ class APIRouter(routing.Router):
             ), "A path prefix must not end with '/', as the routes will start with '/'"
         self.prefix = prefix
         if tags:
-            assert not isinstance(
-                tags, str
-            ), """tags should not be a string: please use ["tag"] instead of "tag"."""
+            if isinstance(tags, str):
+                raise TypeError(f"""tags should not be a string: please use ["{tags}"] instead of "{tags}".""")
         self.tags: List[Union[str, Enum]] = tags or []
         self.dependencies = list(dependencies or []) or []
         self.deprecated = deprecated
@@ -556,9 +555,8 @@ class APIRouter(routing.Router):
         )
         current_tags = self.tags.copy()
         if tags:
-            assert not isinstance(
-                tags, str
-            ), """tags should not be a string: please use ["tag"] instead of "tag"."""
+            if isinstance(tags, str):
+                raise TypeError(f"""tags should not be a string: please use ["{tags}"] instead of "{tags}".""")
             current_tags.extend(tags)
         current_dependencies = self.dependencies.copy()
         if dependencies:
@@ -723,9 +721,8 @@ class APIRouter(routing.Router):
                 )
                 current_tags = []
                 if tags:
-                    assert not isinstance(
-                        tags, str
-                    ), """tags should not be a string: please use ["tag"] instead of "tag"."""
+                    if isinstance(tags, str):
+                        raise TypeError(f"""tags should not be a string: please use ["{tags}"] instead of "{tags}".""")
                     current_tags.extend(tags)
                 if route.tags:
                     current_tags.extend(route.tags)
diff --git a/tests/test_tags.py b/tests/test_tags.py
index 993b81430..3c5993ff3 100644
--- a/tests/test_tags.py
+++ b/tests/test_tags.py
@@ -3,13 +3,13 @@ from fastapi import APIRouter, FastAPI
 
 
 def test_string_is_invalid_in_router_tags():
-    with pytest.raises(AssertionError):
+    with pytest.raises(TypeError):
         APIRouter(tags="test")
 
 def test_string_is_invalid_in_router_route_tags():
     router = APIRouter()
 
-    with pytest.raises(AssertionError):
+    with pytest.raises(TypeError):
         @router.get("", tags="test")
         def test():
             ...
@@ -23,5 +23,5 @@ def test_string_is_invalid_in_include_router_tags():
     def test():
         ...
 
-    with pytest.raises(AssertionError):
+    with pytest.raises(TypeError):
         app.include_router(router, prefix="/test", tags="test")
\ No newline at end of file