Add --strip-extras option to pip-compile for producing constraint compatible output

piptools/scripts/compile.py

@@ -162,6 +162,12 @@ def _get_default_option(option_name: str) -> Any:
         )
     ),
 )
+@click.option(
+    "--strip-extras",
+    is_flag=True,
+    default=False,
+    help="Assure output file is constraints compatible, avoiding use of extras.",
+)
 @click.option(
     "--generate-hashes",
     is_flag=True,
@@ -236,6 +242,7 @@ def cli(
     upgrade_packages: Tuple[str, ...],
     output_file: Union[LazyFile, IO[Any], None],
     allow_unsafe: bool,
+    strip_extras: bool,
     generate_hashes: bool,
     reuse_hashes: bool,
     src_files: Tuple[str, ...],
@@ -457,6 +464,7 @@ def cli(
         emit_index_url=emit_index_url,
         emit_trusted_host=emit_trusted_host,
         annotate=annotate,
+        strip_extras=strip_extras,
         generate_hashes=generate_hashes,
         default_index_url=repository.DEFAULT_INDEX_URL,
         index_urls=repository.finder.index_urls,

piptools/writer.py

@@ -61,6 +61,7 @@ def __init__(
         emit_index_url: bool,
         emit_trusted_host: bool,
         annotate: bool,
+        strip_extras: bool,
         generate_hashes: bool,
         default_index_url: str,
         index_urls: Iterable[str],
@@ -77,6 +78,7 @@ def __init__(
         self.emit_index_url = emit_index_url
         self.emit_trusted_host = emit_trusted_host
         self.annotate = annotate
+        self.strip_extras = strip_extras
         self.generate_hashes = generate_hashes
         self.default_index_url = default_index_url
         self.index_urls = index_urls
@@ -234,6 +236,8 @@ def _format_requirement(
         ireq_hashes = (hashes if hashes is not None else {}).get(ireq)
 
         line = format_requirement(ireq, marker=marker, hashes=ireq_hashes)
+        if self.strip_extras:
+            line = re.sub(r"\[.+?\]", "", line)
 
         if not self.annotate:
             return line

tests/conftest.py

@@ -244,10 +244,14 @@ def make_package(tmp_path):
     Make a package from a given name, version and list of required packages.
     """
 
-    def _make_package(name, version="0.1", install_requires=None):
+    def _make_package(name, version="0.1", install_requires=None, extras_require=None):
+
         if install_requires is None:
             install_requires = []
 
+        if extras_require is None:
+            extras_require = dict()
+
         install_requires_str = "[{}]".format(
             ",".join(f"{package!r}" for package in install_requires)
         )
@@ -267,6 +271,7 @@ def _make_package(name, version="0.1", install_requires=None):
                         author_email="pip-tools@localhost",
                         url="https://github.com/jazzband/pip-tools",
                         install_requires={install_requires_str},
+                        extras_require={extras_require},
                     )
                     """
                 )

tests/test_cli_compile.py

@@ -1837,3 +1837,29 @@ def test_extras_fail_with_requirements_in(runner, tmpdir):
     assert out.exit_code == 2
     exp = "--extra has effect only with setup.py and PEP-517 input formats"
     assert exp in out.stderr
+
+
+def test_cli_compile_strip_extras(runner, make_package, make_sdist, tmpdir):
+    """
+    Assures that --strip-extras removes mention of extras from output.
+    """
+    test_package_1 = make_package(
+        "test_package_1", version="0.1", extras_require={"more": "test_package_2"}
+    )
+    test_package_2 = make_package(
+        "test_package_2",
+        version="0.1",
+    )
+    dists_dir = tmpdir / "dists"
+
+    for pkg in (test_package_1, test_package_2):
+        make_sdist(pkg, dists_dir)
+
+    with open("requirements.in", "w") as reqs_out:
+        reqs_out.write("test_package_1[more]")
+
+    out = runner.invoke(cli, ["--strip-extras", "--find-links", str(dists_dir)])
+
+    assert out.exit_code == 0, out
+    assert "test-package-2==0.1" in out.stderr
+    assert "[more]" not in out.stderr

tests/test_writer.py

@@ -44,6 +44,7 @@ def writer(tmpdir_cwd):
             allow_unsafe=False,
             find_links=[],
             emit_find_links=True,
+            strip_extras=False,
         )
         yield writer