Fix: Improve error message for invalid template variables in virtualenvs.prompt

src/poetry/utils/env/env_manager.py

@@ -19,6 +19,7 @@
 from cleo.io.null_io import NullIO
 from poetry.core.constraints.version import Version
 
+from poetry.console.exceptions import PoetryConsoleError
 from poetry.toml.file import TOMLFile
 from poetry.utils._compat import WINDOWS
 from poetry.utils._compat import encode
@@ -441,10 +442,20 @@ def create_venv(
             venv = venv_path / name
 
         if venv_prompt is not None:
-            venv_prompt = venv_prompt.format(
-                project_name=self._poetry.package.name or "virtualenv",
-                python_version=python.minor_version.to_string(),
-            )
+            try:
+                venv_prompt = venv_prompt.format(
+                    project_name=self._poetry.package.name or "virtualenv",
+                    python_version=python.minor_version.to_string(),
+                )
+            except KeyError as e:
+                raise PoetryConsoleError(
+                    f"Invalid template variable '{e.args[0]}' in 'virtualenvs.prompt' setting.\n"
+                    f"Valid variables are: {{project_name}}, {{python_version}}"
+                ) from e
+            except ValueError as e:
+                raise PoetryConsoleError(
+                    f"Invalid template string in 'virtualenvs.prompt' setting: {e}"
+                ) from e
 
         if not venv.exists():
             if create_venv is False:

tests/utils/env/test_env_manager.py

@@ -13,6 +13,8 @@
 
 from poetry.core.constraints.version import Version
 
+from poetry.config.config import Config
+from poetry.console.exceptions import PoetryConsoleError
 from poetry.toml.file import TOMLFile
 from poetry.utils.env import GET_BASE_PREFIX
 from poetry.utils.env import GET_PYTHON_VERSION_ONELINER
@@ -1302,3 +1304,30 @@ def test_generate_env_name_uses_real_path(
     venv_name1 = EnvManager.generate_env_name("simple-project", "the_real_dir")
     venv_name2 = EnvManager.generate_env_name("simple-project", "linked_dir")
     assert venv_name1 == venv_name2
+
+
+def test_create_venv_invalid_prompt_template_variable(
+    manager: EnvManager, poetry: Poetry, config: Config
+) -> None:
+    config.merge({"virtualenvs": {"prompt": "{project_name}-{invalid_var}"}})
+
+    with pytest.raises(PoetryConsoleError) as exc_info:
+        manager.create_venv()
+
+    assert "Invalid template variable 'invalid_var'" in str(exc_info.value)
+    assert "Valid variables are: {project_name}, {python_version}" in str(
+        exc_info.value
+    )
+
+
+def test_create_venv_malformed_prompt_template(
+    manager: EnvManager, poetry: Poetry, config: Config
+) -> None:
+    config.merge({"virtualenvs": {"prompt": "{project_name"}})  # Missing closing brace
+
+    with pytest.raises(PoetryConsoleError) as exc_info:
+        manager.create_venv()
+
+    assert "Invalid template string in 'virtualenvs.prompt' setting" in str(
+        exc_info.value
+    )