locker: ensure correct handling of extras export

Previously, when determining nested dependencies, the check for
activated extras/features of top level dependencies were done after the
nested dependencies were processed. This lead to exports containing
in active extras. This change resolves this by pre-selecting top level
packages prior to identifying nested dependencies.

(cherry picked from commit 2b6f82e9494b99bdb04d0dac90f87eb23548e4a5)

poetry/packages/locker.py

@@ -318,20 +318,30 @@ class Locker(object):
                 )
             )
 
-        for dependency in self.get_project_dependencies(
-            project_requires=project_requires,
-            locked_packages=repository.packages,
-            with_nested=True,
-        ):
+        # If a package is optional and we haven't opted in to it, do not select
+        selected = []
+        for dependency in project_requires:
             try:
                 package = repository.find_packages(dependency=dependency)[0]
             except IndexError:
                 continue
 
-            # If a package is optional and we haven't opted in to it, continue
             if extra_package_names is not None and (
                 package.optional and package.name not in extra_package_names
             ):
+                # a package is locked as optional, but is not activated via extras
+                continue
+
+            selected.append(dependency)
+
+        for dependency in self.get_project_dependencies(
+            project_requires=selected,
+            locked_packages=repository.packages,
+            with_nested=True,
+        ):
+            try:
+                package = repository.find_packages(dependency=dependency)[0]
+            except IndexError:
                 continue
 
             for extra in dependency.extras:

tests/utils/test_exporter.py

@@ -544,8 +544,17 @@ foo==1.2.3 \\
     assert expected == content
 
 
-def test_exporter_exports_requirements_txt_with_optional_packages_if_opted_in(
-    tmp_dir, poetry
+@pytest.mark.parametrize(
+    "extras,lines",
+    [
+        (None, ["foo==1.2.3"]),
+        (False, ["foo==1.2.3"]),
+        (True, ["bar==4.5.6", "foo==1.2.3", "spam==0.1.0"]),
+        (["feature_bar"], ["bar==4.5.6", "foo==1.2.3", "spam==0.1.0"]),
+    ],
+)
+def test_exporter_exports_requirements_txt_with_optional_packages(
+    tmp_dir, poetry, extras, lines
 ):
     poetry.locker.mock_lock_data(
         {
@@ -590,22 +599,16 @@ def test_exporter_exports_requirements_txt_with_optional_packages_if_opted_in(
         Path(tmp_dir),
         "requirements.txt",
         dev=True,
-        extras=["feature_bar"],
+        with_hashes=False,
+        extras=extras,
     )
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
 
-    expected = """\
-bar==4.5.6 \\
-    --hash=sha256:67890
-foo==1.2.3 \\
-    --hash=sha256:12345
-spam==0.1.0 \\
-    --hash=sha256:abcde
-"""
+    expected = "\n".join(lines)
 
-    assert expected == content
+    assert content.strip() == expected
 
 
 def test_exporter_can_export_requirements_txt_with_git_packages(tmp_dir, poetry):