From bcbf4416c321acddbcf49273a668c3a52b646a23 Mon Sep 17 00:00:00 2001
From: Marcelo Trylesinski <marcelotryle@gmail.com>
Date: Sun, 9 Jul 2023 21:13:56 +0200
Subject: [PATCH] Raise `ImportError` on circular import (#2040)

Co-authored-by: Michael Jones <4087139+mikeedjones@users.noreply.github.com>
---
 tests/importer/circular_import_a.py |  4 ++++
 tests/importer/circular_import_b.py |  4 ++++
 tests/importer/test_importer.py     | 10 ++++++++++
 uvicorn/importer.py                 |  2 +-
 4 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 tests/importer/circular_import_a.py
 create mode 100644 tests/importer/circular_import_b.py

diff --git a/tests/importer/circular_import_a.py b/tests/importer/circular_import_a.py
new file mode 100644
index 000000000..7d68ad8d0
--- /dev/null
+++ b/tests/importer/circular_import_a.py
@@ -0,0 +1,4 @@
+# Used by test_importer.py
+from .circular_import_b import foo  # noqa
+
+bar = 123
diff --git a/tests/importer/circular_import_b.py b/tests/importer/circular_import_b.py
new file mode 100644
index 000000000..4854a80ee
--- /dev/null
+++ b/tests/importer/circular_import_b.py
@@ -0,0 +1,4 @@
+# Used by test_importer.py
+from .circular_import_a import bar  # noqa
+
+foo = 123
diff --git a/tests/importer/test_importer.py b/tests/importer/test_importer.py
index d9eb3a86b..371fdcaf9 100644
--- a/tests/importer/test_importer.py
+++ b/tests/importer/test_importer.py
@@ -41,3 +41,13 @@ def test_no_import_needed() -> None:
 
     instance = import_from_string(TemporaryFile)
     assert instance == TemporaryFile
+
+
+def test_circular_import_error() -> None:
+    with pytest.raises(ImportError) as exc_info:
+        import_from_string("tests.importer.circular_import_a:bar")
+    expected = (
+        "cannot import name 'bar' from partially initialized module "
+        "'tests.importer.circular_import_a' (most likely due to a circular import)"
+    )
+    assert expected in str(exc_info.value)
diff --git a/uvicorn/importer.py b/uvicorn/importer.py
index e612bf134..338eba25c 100644
--- a/uvicorn/importer.py
+++ b/uvicorn/importer.py
@@ -19,7 +19,7 @@ def import_from_string(import_str: Any) -> Any:
 
     try:
         module = importlib.import_module(module_str)
-    except ImportError as exc:
+    except ModuleNotFoundError as exc:
         if exc.name != module_str:
             raise exc from None
         message = 'Could not import module "{module_str}".'