Enable --only-deps with FLIT_ALLOW_INVALID

flit_core/flit_core/common.py

@@ -56,9 +56,15 @@ def __init__(self, name, directory=Path()):
                 .format(name, ", ".join([str(p) for p in sorted(existing)]))
             )
         elif not existing:
-            raise ValueError("No file/folder found for module {}".format(name))
-
-        self.source_dir = directory / self.prefix
+            if os.environ.get("FLIT_ALLOW_INVALID"):
+                log.warning(
+                    "Allowing invalid data (FLIT_ALLOW_INVALID set). No file/folder found for module {}"
+                    .format(name)
+                )
+            else:
+                raise ValueError("No file/folder found for module {}".format(name))
+        else:
+            self.source_dir = directory / self.prefix
 
         if '.' in name:
             self.namespace_package_name = name.rpartition('.')[0]

flit_core/flit_core/config.py

@@ -281,6 +281,12 @@ def description_from_file(rel_path: str, proj_dir: Path, guess_mimetype=True):
         with desc_path.open('r', encoding='utf-8') as f:
             raw_desc = f.read()
     except IOError as e:
+        if os.environ.get('FLIT_ALLOW_INVALID'):
+            log.warning(
+                "Allowing invalid data (FLIT_ALLOW_INVALID set). Description file {} does not exist"
+                .format(desc_path)
+            )
+            return None, None
         if e.errno == errno.ENOENT:
             raise ConfigError(
                 "Description file {} does not exist".format(desc_path)

tests/samples/missing-description-file.toml

@@ -7,3 +7,4 @@ author = "Sir Robin"
 author-email = "robin@camelot.uk"
 home-page = "http://github.com/sirrobin/missingdescriptionfile"
 description-file = "definitely-missing.rst"
+requires = ["requests"]

tests/samples/missing-module.toml

@@ -0,0 +1,10 @@
+[build-system]
+requires = ["flit"]
+
+[tool.flit.metadata]
+module = "definitelymissingmodule"
+author = "Sir Robin"
+author-email = "robin@camelot.uk"
+home-page = "http://github.com/sirrobin/module1"
+description-file = "EG_README.rst"
+requires = ["requests"]

tests/test_install.py

@@ -13,6 +13,7 @@
 
 from flit import install
 from flit.install import Installer, _requires_dist_to_pip_requirement, DependencyError
+from flit_core.config import ConfigError
 import flit_core.tests
 
 samples_dir = pathlib.Path(__file__).parent / 'samples'
@@ -278,6 +279,32 @@ def test_install_requires(self):
         assert len(calls) == 1
         assert calls[0]['argv'][1:5] == ['-m', 'pip', 'install', '-r']
 
+    def test_install_only_deps(self):
+        """Test if we can install using --only-deps with the pyproject.toml, and without the README or module folder"""
+        os.environ.setdefault('FLIT_ALLOW_INVALID', '1')
+        try:
+            ins = Installer.from_ini_path(
+                samples_dir / 'missing-description-file.toml', user=False, python='mock_python'
+            )
+
+            with MockCommand('mock_python') as mockpy:
+                ins.install_requirements()
+            calls = mockpy.get_calls()
+            assert len(calls) == 1
+            assert calls[0]['argv'][1:5] == ['-m', 'pip', 'install', '-r']
+        finally:
+            del os.environ['FLIT_ALLOW_INVALID']
+
+    def test_install_only_deps_fail(self):
+        with pytest.raises(ConfigError, match=r"Description file .* does not exist"):
+            Installer.from_ini_path(
+                samples_dir / 'missing-description-file.toml', user=False, python='mock_python'
+            )
+        with pytest.raises(ValueError, match=r"No file/folder found for module definitelymissingmodule"):
+            Installer.from_ini_path(
+                samples_dir / 'missing-module.toml', user=False, python='mock_python'
+            )
+
     def test_install_reqs_my_python_if_needed_pep621(self):
         ins = Installer.from_ini_path(
             core_samples_dir / 'pep621_nodynamic' / 'pyproject.toml',