Change back into inline and add tests

src/poetry/utils/env.py

@@ -818,13 +818,6 @@ def remove(self, python: str) -> Env:
 
         return VirtualEnv(venv_path, venv_path)
 
-    def get_formatted_prompt(self, python_version: str) -> str:
-        venv_prompt = self._poetry.config.get("virtualenvs.prompt")
-        return venv_prompt.format(
-            project_name=self._poetry.package.name or "virtualenv",
-            python_version=python_version,
-        )
-
     def create_venv(
         self,
         io: IO,
@@ -954,7 +947,10 @@ def create_venv(
             venv = venv_path / name
 
         if venv_prompt is not None:
-            venv_prompt = self.get_formatted_prompt(python_minor)
+            venv_prompt = venv_prompt.format(
+                project_name=self._poetry.package.name or "virtualenv",
+                python_version=python_minor,
+            )
 
         if not venv.exists():
             if create_venv is False:

tests/fixtures/no_name_project/README.rst

@@ -0,0 +1,2 @@
+No name project
+===============

tests/fixtures/no_name_project/pyproject.toml

@@ -0,0 +1,18 @@
+[tool.poetry]
+name = ""
+version = "1.2.3"
+description = "This project has no name"
+authors = [
+    "Sébastien Eustace <sebastien@eustace.io>"
+]
+license = "MIT"
+
+readme = "README.rst"
+
+
+# Requirements
+[tool.poetry.dependencies]
+python = "~2.7 || ^3.6"
+
+[tool.poetry.group.dev.dependencies]
+pytest = "~3.4"

tests/utils/test_env.py

@@ -79,10 +79,19 @@ def poetry(project_factory: ProjectFactory) -> Poetry:
     return project_factory("simple", source=fixture)
 
 
+@pytest.fixture()
+def no_name_poetry(project_factory: ProjectFactory) -> Poetry:
+    fixture = Path(__file__).parent.parent / "fixtures" / "no_name_project"
+    return project_factory("no", source=fixture)
+
 @pytest.fixture()
 def manager(poetry: Poetry) -> EnvManager:
     return EnvManager(poetry)
 
+@pytest.fixture()
+def no_name_manager(no_name_poetry: Poetry) -> EnvManager:
+    return EnvManager(no_name_poetry)
+
 
 def test_virtualenvs_with_spaces_in_their_path_work_as_expected(
     tmp_dir: str, manager: EnvManager
@@ -1415,3 +1424,40 @@ def test_build_environment_not_called_without_build_script_specified(
     with build_environment(poetry, project_env) as env:
         assert env == project_env
         assert not env.executed
+
+
+def test_create_venv_project_name_empty_sets_correct_prompt(
+    no_name_manager: EnvManager,
+    no_name_poetry: Poetry,
+    config: Config,
+    mocker: MockerFixture,
+    config_virtualenvs_path: Path,
+):
+    if "VIRTUAL_ENV" in os.environ:
+        del os.environ["VIRTUAL_ENV"]
+
+    no_name_poetry.package.python_versions = "^3.7"
+    venv_name = no_name_manager.generate_env_name("", str(no_name_poetry.file.parent))
+
+    mocker.patch("sys.version_info", (2, 7, 16))
+    mocker.patch(
+        "subprocess.check_output",
+        side_effect=check_output_wrapper(Version.parse("3.7.5")),
+    )
+    m = mocker.patch(
+        "poetry.utils.env.EnvManager.build_venv", side_effect=lambda *args, **kwargs: ""
+    )
+
+    no_name_manager.create_venv(NullIO())
+
+    m.assert_called_with(
+        config_virtualenvs_path / f"{venv_name}-py3.7",
+        executable="python3",
+        flags={
+            "always-copy": False,
+            "system-site-packages": False,
+            "no-pip": False,
+            "no-setuptools": False,
+        },
+        prompt="virtualenv-py3.7",
+    )