Support pyproject.toml without build system to detect project name

news/84.feature

@@ -0,0 +1 @@
+Support pyproject.toml without build system to detect project name.

src/pip_deepfreeze/project_name.py

@@ -94,9 +94,8 @@ def get_project_name_from_pyproject_toml_pep621(
     pyproject_toml: Optional[PyProjectToml],
 ) -> Optional[str]:
     log_info(".", nl=False)
-    if not _get_build_backend(pyproject_toml):
+    if not pyproject_toml:
         return None
-    assert pyproject_toml
     project_name = pyproject_toml.get("project", {}).get("name")
     if not project_name:
         return None

tests/test_project_name.py

@@ -110,6 +110,22 @@ def test_get_project_name_from_pyproject_toml_pep621_no_project(tmp_path):
     )
 
 
+def test_get_project_name_from_pyproject_toml_pep621_no_build_system(tmp_path):
+    (tmp_path / "pyproject.toml").write_text(
+        textwrap.dedent(
+            """\
+            [project]
+            name = "theproject"
+            """
+        )
+    )
+    assert (
+        get_project_name_from_pyproject_toml_pep621(_load_pyproject_toml(tmp_path))
+        == "theproject"
+    )
+    assert get_project_name(sys.executable, tmp_path) == "theproject"
+
+
 def test_project_name_from_pep517_setup_py(tmp_path):
     setup_py = tmp_path / "setup.py"
     setup_py.write_text(