Fix a regression bug came from #731 PR

piptools/scripts/compile.py

@@ -79,7 +79,7 @@ def cli(verbose, quiet, dry_run, pre, rebuild, find_links, index_url, extra_inde
 
     if src_files == ('-',) and not output_file:
         raise click.BadParameter('--output-file is required if input is from stdin')
-    elif src_files == ('setup.py',):
+    elif src_files == ('setup.py',) and not output_file:
         output_file = DEFAULT_REQUIREMENTS_OUTPUT_FILE
 
     if len(src_files) > 1 and not output_file:

tests/test_cli_compile.py

@@ -77,11 +77,8 @@ def test_command_line_overrides_pip_conf(pip_conf):
         assert 'Using indexes:\n  http://override.com' in out.output
 
 
-@pytest.mark.parametrize('cli_args', [
-    [],
-    ['setup.py'],
-])
-def test_command_line_setuptools_read(pip_conf, cli_args):
+@pytest.mark.usefixtures('pip_conf')
+def test_command_line_setuptools_read():
     runner = CliRunner()
     with runner.isolated_filesystem():
         package = open('setup.py', 'w')
@@ -90,13 +87,42 @@ def test_command_line_setuptools_read(pip_conf, cli_args):
             setup(install_requires=[])
         """))
         package.close()
-        out = runner.invoke(cli, cli_args)
+        out = runner.invoke(cli)
 
         # check that pip-compile generated a configuration
         assert 'This file is autogenerated by pip-compile' in out.output
         assert os.path.exists('requirements.txt')
 
 
+@pytest.mark.usefixtures('pip_conf')
+@pytest.mark.parametrize('options, expected_output_file', [
+    # For the `pip-compile` output file should be "requirements.txt"
+    ([], 'requirements.txt'),
+    # For the `pip-compile --output-file=output.txt` output file should be "output.txt"
+    (['--output-file', 'output.txt'], 'output.txt'),
+    # For the `pip-compile setup.py` output file should be "requirements.txt"
+    (['setup.py'], 'requirements.txt'),
+    # For the `pip-compile setup.py --output-file=output.txt` output file should be "output.txt"
+    (['setup.py', '--output-file', 'output.txt'], 'output.txt'),
+])
+def test_command_line_setuptools_output_file(options, expected_output_file):
+    """
+    Test the output files for setup.py as a requirement file.
+    """
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        package = open('setup.py', 'w')
+        package.write(dedent("""\
+            from setuptools import setup
+            setup(install_requires=[])
+        """))
+        package.close()
+
+        out = runner.invoke(cli, options)
+        assert out.exit_code == 0
+        assert os.path.exists(expected_output_file)
+
+
 def test_find_links_option(pip_conf):
 
     assert os.path.exists(pip_conf)