Fix for sync error when the ireqs being merged have no names

piptools/sync.py

@@ -104,7 +104,11 @@ def merge(
                 if existing_ireq:
                     # NOTE: We check equality here since we can assume that the
                     # requirements are all pinned
-                    if ireq.specifier != existing_ireq.specifier:
+                    if (
+                        ireq.req
+                        and existing_ireq.req
+                        and ireq.specifier != existing_ireq.specifier
+                    ):
                         raise IncompatibleRequirements(ireq, existing_ireq)
 
             # TODO: Always pick the largest specifier in case of a conflict

tests/test_cli_sync.py

@@ -3,6 +3,7 @@
 import os
 import subprocess
 import sys
+from pathlib import Path
 from unittest import mock
 
 import pytest
@@ -128,6 +129,31 @@ def test_merge_error(req_lines, should_raise, runner):
         assert out.exit_code == 1
 
 
+@pytest.mark.parametrize(
+    "req_line",
+    (
+        "file:.",
+        "-e file:.",
+    ),
+)
+@mock.patch("piptools.sync.run")
+def test_merge_no_name_urls(run, req_line, runner):
+    """
+    Test sync succeeds when merging requirements that lack names.
+    """
+    reqs_paths = [
+        Path(name).absolute() for name in ("requirements.txt", "dev_requirements.txt")
+    ]
+
+    for reqs_path in reqs_paths:
+        with reqs_path.open("w") as req_out:
+            req_out.write(f"{req_line} \n")
+
+    out = runner.invoke(cli, [str(path) for path in reqs_paths])
+    assert out.exit_code == 0
+    assert run.call_count == 2
+
+
 @pytest.mark.parametrize(
     ("cli_flags", "expected_install_flags"),
     (

tests/test_sync.py

@@ -115,6 +115,26 @@ def test_merge_urls(from_line):
     )
 
 
+@pytest.mark.parametrize(
+    "install_req",
+    (
+        "from_line",
+        "from_editable",
+    ),
+)
+def test_merge_no_name_urls(install_req, request):
+    install_req = request.getfixturevalue(install_req)
+    url = "file:///example.zip"
+    requirements = [
+        install_req(url),
+        install_req(url),
+    ]
+
+    assert Counter(requirements[1:]) == Counter(
+        merge(requirements, ignore_conflicts=False)
+    )
+
+
 def test_diff_should_do_nothing():
     installed = []  # empty env
     reqs = []  # no requirements