Direct references show extra requirements in .txt

piptools/utils.py

@@ -152,7 +152,9 @@ def _build_direct_reference_best_efforts(ireq: InstallRequirement) -> str:
 
     # If we get here then we have a requirement that supports direct reference.
     # We need to remove the egg if it exists and keep the rest of the fragments.
-    direct_reference = f"{ireq.name.lower()} @ {ireq.link.url_without_fragment}"
+    lowered_ireq_name = ireq.name.lower()
+    extras = f"[{','.join(sorted(ireq.extras))}]" if ireq.extras else ""
+    direct_reference = f"{lowered_ireq_name}{extras} @ {ireq.link.url_without_fragment}"
     fragments = []
 
     # Check if there is any fragment to add to the URI.

tests/test_cli_compile.py

@@ -659,7 +659,10 @@ def test_direct_reference_with_extras(runner):
         )
     out = runner.invoke(cli, ["-n", "--rebuild"])
     assert out.exit_code == 0
-    assert "pip-tools @ git+https://github.com/jazzband/pip-tools@6.2.0" in out.stderr
+    assert (
+        "pip-tools[coverage,testing] @ git+https://github.com/jazzband/pip-tools@6.2.0"
+        in out.stderr
+    )
     assert "pytest==" in out.stderr
     assert "pytest-cov==" in out.stderr
 

tests/test_utils.py

@@ -73,6 +73,11 @@ def test_format_requirement(from_line):
             "example @ https://example.com/example.zip?egg=test",
             id="direct reference with egg in query",
         ),
+        pytest.param(
+            "example[b,c,a] @ https://example.com/example.zip",
+            "example[a,b,c] @ https://example.com/example.zip",
+            id="direct reference with optional dependency",
+        ),
         pytest.param(
             "file:./vendor/package.zip",
             "file:./vendor/package.zip",