Use pep517 to load project metadata

Fix jazzband#908, first step towards addressing jazzband#1047.

piptools/scripts/compile.py

@@ -8,8 +8,12 @@
 import click
 from click import Command
 from click.utils import safecall
+from pep517 import meta
 from pip._internal.commands import create_command
-from pip._internal.req.constructors import install_req_from_line
+from pip._internal.req.constructors import (
+    install_req_from_line,
+    install_req_from_req_string,
+)
 from pip._internal.utils.misc import redact_auth_from_url
 
 from .._compat import parse_requirements
@@ -373,21 +377,14 @@ def cli(
     constraints = []
     for src_file in src_files:
         is_setup_file = os.path.basename(src_file) == "setup.py"
-        if is_setup_file or src_file == "-":
+        if src_file == "-":
             # pip requires filenames and not files. Since we want to support
             # piping from stdin, we need to briefly save the input from stdin
             # to a temporary file and have pip read that.  also used for
             # reading requirements from install_requires in setup.py.
             tmpfile = tempfile.NamedTemporaryFile(mode="wt", delete=False)
-            if is_setup_file:
-                from distutils.core import run_setup
-
-                dist = run_setup(src_file)
-                tmpfile.write("\n".join(dist.install_requires))
-                comes_from = f"{dist.get_name()} ({src_file})"
-            else:
-                tmpfile.write(sys.stdin.read())
-                comes_from = "-r -"
+            tmpfile.write(sys.stdin.read())
+            comes_from = "-r -"
             tmpfile.flush()
             reqs = list(
                 parse_requirements(
@@ -400,6 +397,15 @@ def cli(
             for req in reqs:
                 req.comes_from = comes_from
             constraints.extend(reqs)
+        elif is_setup_file:
+            dist = meta.load(".")
+            comes_from = f"{dist.metadata.get_all('Name')[0]} ({src_file})"
+            constraints.extend(
+                [
+                    install_req_from_req_string(req, comes_from=comes_from)
+                    for req in dist.requires or []
+                ]
+            )
         else:
             constraints.extend(
                 parse_requirements(
@@ -421,7 +427,9 @@ def cli(
 
     # Filter out pip environment markers which do not match (PEP496)
     constraints = [
-        req for req in constraints if req.markers is None or req.markers.evaluate()
+        req
+        for req in constraints
+        if req.markers is None or req.markers.evaluate(dict(extra=None))
     ]
 
     log.debug("Using indexes:")

setup.cfg

@@ -30,6 +30,7 @@ packages = find:
 zip_safe = false
 install_requires =
     click >= 7
+    pep517
     pip >= 20.1
 
 [options.packages.find]

tests/test_cli_compile.py

@@ -39,7 +39,17 @@ def test_command_line_overrides_pip_conf(pip_with_index_conf, runner):
     assert "Using indexes:\n  http://override.com" in out.stderr
 
 
-def test_command_line_setuptools_read(pip_conf, runner):
+def test_command_line_setuptools_read(make_pip_conf, runner):
+    make_pip_conf(
+        dedent(
+            f"""\
+            [global]
+            disable-pip-version-check = True
+            find-links = {MINIMAL_WHEELS_PATH}
+            """
+        )
+    )
+
     with open("setup.py", "w") as package:
         package.write(
             dedent(
@@ -87,11 +97,20 @@ def test_command_line_setuptools_read(pip_conf, runner):
     ),
 )
 def test_command_line_setuptools_output_file(
-    pip_conf, runner, options, expected_output_file
+    make_pip_conf, runner, options, expected_output_file
 ):
     """
     Test the output files for setup.py as a requirement file.
     """
+    make_pip_conf(
+        dedent(
+            f"""\
+            [global]
+            find-links = {MINIMAL_WHEELS_PATH}
+            """
+        )
+    )
+
     with open("setup.py", "w") as package:
         package.write(
             dedent(