exporter: print warning instead of raising an error when exporting a …

…constraints.txt with editable dependencies

src/poetry_plugin_export/command.py

@@ -100,7 +100,7 @@ def handle(self) -> None:
                 f"Extra [{', '.join(sorted(invalid_extras))}] is not specified."
             )
 
-        exporter = Exporter(self.poetry)
+        exporter = Exporter(self.poetry, self.io)
         exporter.only_groups(list(self.activated_groups))
         exporter.with_extras(list(extras))
         exporter.with_hashes(not self.option("without-hashes"))

src/poetry_plugin_export/exporter.py

@@ -34,8 +34,9 @@ class Exporter:
         FORMAT_REQUIREMENTS_TXT: "_export_requirements_txt",
     }
 
-    def __init__(self, poetry: Poetry) -> None:
+    def __init__(self, poetry: Poetry, io: IO) -> None:
         self._poetry = poetry
+        self._io = io
         self._with_hashes = True
         self._with_credentials = False
         self._with_urls = True
@@ -106,10 +107,12 @@ def _export_generic_txt(
 
             if package.develop:
                 if not allow_editable:
-                    raise RuntimeError(
-                        f"{package.pretty_name} is locked in develop (editable) mode,"
-                        " which is incompatible with the constraints.txt format."
+                    self._io.write_error_line(
+                        f"<warning>Warning: {package.pretty_name} is locked in develop"
+                        " (editable) mode, which is incompatible with the"
+                        " constraints.txt format.</warning>"
                     )
+                    continue
                 line += "-e "
 
             requirement = dependency.to_pep_508(with_extras=False)

tests/command/test_command_export.py

@@ -229,3 +229,37 @@ def test_export_with_urls(
     monkeypatch.setattr(Exporter, "with_urls", mock_export)
     tester.execute("--without-urls")
     mock_export.assert_called_once_with(False)
+
+
+def test_export_exports_constraints_txt_with_warnings(
+    fixture_root: Path,
+    project_factory: ProjectFactory,
+    command_tester_factory: CommandTesterFactory,
+) -> None:
+    pyproject_content = f"""\
+[tool.poetry]
+name = "simple-project"
+version = "1.2.3"
+description = "Some description."
+authors = [
+    "Sébastien Eustace <sebastien@eustace.io>"
+]
+
+[tool.poetry.dependencies]
+python = "^3.6"
+baz = ">1.0"
+project-with-nested-local = {{ path = \
+"{(fixture_root / "project_with_nested_local").as_posix()}", develop = true }}
+"""
+    poetry = project_factory(name="export", pyproject_content=pyproject_content)
+    tester = command_tester_factory("export", poetry=poetry)
+    tester.execute("--format constraints.txt")
+
+    develop_warning = (
+        "Warning: project-with-nested-local is locked in develop (editable) mode, which"
+        " is incompatible with the constraints.txt format.\n"
+    )
+    expected = 'baz==2.0.0 ; python_version >= "3.6" and python_version < "4.0"\n'
+
+    assert develop_warning in tester.io.fetch_error()
+    assert tester.io.fetch_output() == expected