Fix bug with add_python='3.9' (#2751)

* Fix bug with add_python='3.9'

* Remove debugging print and add an assertion about the context mount

modal/image.py

@@ -1506,7 +1506,8 @@ def _registry_setup_commands(
                 "COPY /python/. /usr/local",
                 "ENV TERMINFO_DIRS=/etc/terminfo:/lib/terminfo:/usr/share/terminfo:/usr/lib/terminfo",
             ]
-            if add_python < "3.13":
+            python_minor = add_python.split(".")[1]
+            if int(python_minor) < 13:
                 # Previous versions did not include the `python` binary, but later ones do.
                 # (The important factor is not the Python version itself, but the standalone dist version.)
                 # We insert the command in the list at the position it was previously always added

test/conftest.py

@@ -47,7 +47,7 @@
 from modal.cls import _Cls
 from modal.functions import _Function
 from modal.image import ImageBuilderVersion
-from modal.mount import client_mount_name
+from modal.mount import PYTHON_STANDALONE_VERSIONS, client_mount_name, python_standalone_mount_name
 from modal_proto import api_grpc, api_pb2
 
 
@@ -233,6 +233,13 @@ def __init__(self, blob_host, blobs, credentials):
         self.default_published_client_mount = "mo-123"
         self.deployed_mounts = {
             (client_mount_name(), api_pb2.DEPLOYMENT_NAMESPACE_GLOBAL): self.default_published_client_mount,
+            **{
+                (
+                    python_standalone_mount_name(version),
+                    api_pb2.DEPLOYMENT_NAMESPACE_GLOBAL,
+                ): f"mo-py{version.replace('.', '')}"
+                for version in PYTHON_STANDALONE_VERSIONS
+            },
         }
 
         self.deployed_nfss = {}

test/image_test.py

@@ -323,6 +323,29 @@ def test_debian_slim_apt_install(builder_version, servicer, client):
         assert any("pip install numpy" in cmd for cmd in layers[2].dockerfile_commands)
 
 
+def test_from_registry_add_python(builder_version, servicer, client):
+    app = App(image=Image.from_registry("ubuntu", add_python="3.9"))
+    app.function()(dummy)
+
+    with app.run(client=client):
+        layers = get_image_layers(app.image.object_id, servicer)
+        commands = layers[0].dockerfile_commands
+        assert layers[0].context_mount_id == "mo-py39"
+        assert any("COPY /python/. /usr/local" in cmd for cmd in commands)
+        assert any("ln -s /usr/local/bin/python3" in cmd for cmd in commands)
+
+    if builder_version >= "2024.10":
+        app = App(image=Image.from_registry("ubuntu", add_python="3.13"))
+        app.function()(dummy)
+
+        with app.run(client=client):
+            layers = get_image_layers(app.image.object_id, servicer)
+            commands = layers[0].dockerfile_commands
+            assert layers[0].context_mount_id == "mo-py313"
+            assert any("COPY /python/. /usr/local" in cmd for cmd in commands)
+            assert not any("ln -s /usr/local/bin/python3" in cmd for cmd in commands)
+
+
 def test_image_pip_install_pyproject(builder_version, servicer, client):
     pyproject_toml = os.path.join(os.path.dirname(__file__), "supports/test-pyproject.toml")