usethis-python · nathanjmcdougall · Mar 5, 2025 · Mar 5, 2025 · Mar 5, 2025
diff --git a/src/usethis/_integrations/uv/deps.py b/src/usethis/_integrations/uv/deps.py
@@ -65,26 +65,39 @@ def register_default_group(group: str) -> None:
     This ensures that dependencies in the group will be installed by default.
     """
     if group == "dev":
+        # Note, if the "dev" group is missing already then then we'll respect the
+        # user's choice since they presumably would have added it themselves. So, we
+        # won't register in that case.
         return
 
-    ensure_dev_group_is_defined()
-
-    try:
-        default_groups = get_pyproject_value(["tool", "uv", "default-groups"])
-        if not isinstance(default_groups, list):
-            default_groups = []
-    except KeyError:
-        default_groups = []
+    default_groups = get_default_groups()
 
+    # Choose which groups we want to add
     groups_to_add = []
     if group not in default_groups:
         groups_to_add.append(group)
         # Add "dev" if section is empty or if we're adding a new group and "dev" isn't present
         if (not default_groups or group != "dev") and "dev" not in default_groups:
+            ensure_dev_group_is_defined()
             groups_to_add.append("dev")
 
     if groups_to_add:
-        extend_pyproject_list(["tool", "uv", "default-groups"], groups_to_add)
+        add_default_groups(groups=groups_to_add)
+
+
+def add_default_groups(groups: list[str]) -> None:
+    extend_pyproject_list(["tool", "uv", "default-groups"], groups)
+
+
+def get_default_groups() -> list[str]:
+    try:
+        default_groups = get_pyproject_value(["tool", "uv", "default-groups"])
+        if not isinstance(default_groups, list):
+            default_groups = []
+    except KeyError:
+        default_groups = []
+
+    return default_groups
 
 
 def ensure_dev_group_is_defined() -> None:
@@ -112,8 +125,6 @@ def add_deps_to_group(deps: list[Dependency], group: str) -> None:
     if usethis_config.frozen:
         box_print(f"Install the dependenc{ies} {deps_str}.")
 
-    register_default_group(group)  # Register the group before adding dependencies
-
     for dep in to_add_deps:
         try:
             call_uv_subprocess(
@@ -125,6 +136,9 @@ def add_deps_to_group(deps: list[Dependency], group: str) -> None:
             msg += (Path.cwd() / "pyproject.toml").read_text()
             raise UVDepGroupError(msg) from None
 
+    # Register the group - don't do this before adding the deps in case that step fails
+    register_default_group(group)
+
 
 def is_dep_satisfied_in(dep: Dependency, *, in_: list[Dependency]) -> bool:
     return any(_is_dep_satisfied_by(dep, by=by) for by in in_)

diff --git a/tests/usethis/_integrations/uv/test_deps.py b/tests/usethis/_integrations/uv/test_deps.py
@@ -15,6 +15,7 @@
 from usethis._integrations.uv.deps import (
     Dependency,
     add_deps_to_group,
+    get_default_groups,
     get_dep_groups,
     get_deps_from_group,
     is_dep_in_any_group,
@@ -290,16 +291,18 @@ def mock_call_uv_subprocess(*_, **__):
             usethis._integrations.uv.deps, "call_uv_subprocess", mock_call_uv_subprocess
         )
 
-        with (
-            change_cwd(uv_init_dir),
-            PyprojectTOMLManager(),
-            pytest.raises(
+        # Act, Assert
+        with change_cwd(uv_init_dir), PyprojectTOMLManager():
+            with pytest.raises(
                 UVDepGroupError,
                 match="Failed to add 'pytest' to the 'test' dependency group",
-            ),
-        ):
-            # Act
-            add_deps_to_group([Dependency(name="pytest")], "test")
+            ):
+                add_deps_to_group([Dependency(name="pytest")], "test")
+
+            # Assert contd
+            # We want to check that registration hasn't taken place
+            default_groups = get_default_groups()
+            assert "test" not in default_groups
 
 
 class TestRemoveDepsFromGroup:
@@ -627,3 +630,45 @@ def test_existing_section_adds_dev_with_new_group(self, tmp_path: Path):
             # Assert
             default_groups = get_pyproject_value(["tool", "uv", "default-groups"])
             assert set(default_groups) == {"test", "docs", "dev"}
+
+    def test_dev_not_added_if_missing(self, tmp_path: Path):
+        # Arrange
+        (tmp_path / "pyproject.toml").write_text("""\
+[tool.uv]
+default-groups = ["test"]
+""")
+
+        with change_cwd(tmp_path), PyprojectTOMLManager():
+            # Act
+            register_default_group("test")
+
+            # Assert
+            default_groups = get_pyproject_value(["tool", "uv", "default-groups"])
+            assert set(default_groups) == {"test"}
+
+
+class TestGetDefaultGroups:
+    def test_empty_pyproject_toml(self, tmp_path: Path):
+        # Arrange
+        (tmp_path / "pyproject.toml").touch()
+
+        with change_cwd(tmp_path), PyprojectTOMLManager():
+            # Act
+            result = get_default_groups()
+
+            # Assert
+            assert result == []
+
+    def test_invalid_default_groups(self, tmp_path: Path):
+        # Arrange
+        (tmp_path / "pyproject.toml").write_text("""\
+[tool.uv]
+default-groups = "not a list"
+""")
+
+        with change_cwd(tmp_path), PyprojectTOMLManager():
+            # Act
+            result = get_default_groups()
+
+            # Assert
+            assert result == []