Fixes #10 - do not require a setup.py

If setup.cfg or pyproject.toml present, use a minimal setup.py without
creating a file on disk.

setuptools_conda/__main__.py

@@ -1,5 +1,6 @@
 from pathlib import Path
 from subprocess import call, check_output
+import shlex
 import sys
 import argparse
 import textwrap
@@ -182,7 +183,7 @@ def main():
     )
 
     def run_conda_cmd(cmd, **kwargs):
-        print('[running]:', ' '.join(cmd))
+        print('[running]:', *[shlex.quote(arg) for arg in cmd])
         # Shell=True is necessary on Windows for calls to conda, otherwise we get
         # mysterious breakage. But shell=True with a list of args totally changes this
         # function on unix so we avoid it:
@@ -191,15 +192,8 @@ def run_conda_cmd(cmd, **kwargs):
             sys.exit(rc)
         return rc
 
-    def run(cmd, **kwargs):
-        print('[running]:', ' '.join(cmd))
-        rc = call(cmd, **kwargs)
-        if rc:
-            sys.exit(rc)
-        return rc
-
     def get_output(cmd, **kwargs):
-        print('[running]:', ' '.join(cmd))
+        print('[running]:', *[shlex.quote(arg) for arg in cmd])
         return check_output(cmd, shell=WINDOWS, **kwargs).decode('utf8').strip()
 
     def getargvalue(argname, args):
@@ -220,7 +214,7 @@ def getargvalue(argname, args):
                 return arg.split(f'--{argname}=', 1)[1]
 
     def get_project_name(proj):
-        return get_output([sys.executable, 'setup.py', '--name'], cwd=str(proj))
+        return get_output([sys.executable, *setup_py(proj), '--name'], cwd=str(proj))
 
     def get_build_requires(proj, args):
         arg = 'setup-requires'
@@ -253,7 +247,7 @@ def get_run_requires(proj, args, name):
         if requires is not None:
             print("Using run requirements from [dist_conda]/setup_requires")
             return requires
-        get_output([sys.executable, 'setup.py', 'egg_info'], cwd=str(proj))
+        get_output([sys.executable, *setup_py(proj), 'egg_info'], cwd=str(proj))
         requires_file = Path(proj, f'{name.replace("-", "_")}.egg-info', 'requires.txt')
         requires = requires_file.read_text().splitlines()
         # Ignore extras sections:
@@ -336,6 +330,8 @@ def remove_projects(requirements, projects):
         evaluate_requirements,
         condify_requirement,
         split,
+        setup_py,
+        run,
     )
 
     all_build_requires = []
@@ -370,7 +366,10 @@ def remove_projects(requirements, projects):
         print("\nBuilding...")
         proj = Path(args.projects[0])
         sys.exit(
-            run([sys.executable, 'setup.py', 'dist_conda'] + setup_args, cwd=str(proj))
+            run(
+                [sys.executable, *setup_py(proj), 'dist_conda'] + setup_args,
+                cwd=str(proj),
+            )
         )
 
     print("\nGetting run requirements...")

setuptools_conda/setuptools_conda.py

@@ -1,7 +1,8 @@
 import sys
 import os
 import shutil
-from subprocess import check_call
+from subprocess import call
+import shlex
 from setuptools import Command
 import json
 from textwrap import dedent
@@ -36,6 +37,38 @@
 }
 
 
+# Command line args that can be used in place of "setup.py" for projects that lack a
+# setup.py, runs a minimal setup.py similar to what pip does for projects with no
+# setup.py.
+_SETUP_PY_STUB = [
+    "-c",
+    'import sys, setuptools; sys.argv[0] = __file__ = "setup.py"; setuptools.setup()',
+]
+
+
+def run(cmd, **kwargs):
+    print('[running]:', *[shlex.quote(arg) for arg in cmd])
+    rc = call(cmd, **kwargs)
+    if rc:
+        sys.exit(rc)
+    return rc
+
+
+def setup_py(project_dir):
+    """Returns a list of command line arguments to be used in place of ["setup.py"]. If
+    setup.py exists, then this is just ["setup.py"]. Otherwise, if setup.cfg or
+    pyproject.toml exists, returns args that pass a code snippet to Python with "-c" to
+    execute a minimal setup.py calling setuptools.setup(). If none of pyproject.toml,
+    setup.cfg, or setup.py exists, raises an exception."""
+    if Path(project_dir, 'setup.py').exists():
+        return ['setup.py']
+    elif any(Path(project_dir, s).exists() for s in ['setup.cfg', 'pyproject.toml']):
+        return _SETUP_PY_STUB
+    msg = f"""{project_dir} does not look like a python project directory: contains no
+        setup.py, setup.cfg, or pyproject.toml"""
+    raise RuntimeError(' '.join(msg.split))
+
+
 # Couldn't figure out how to use PyYAML to produce output looking like conda recipes are
 # usually formatted:
 def yaml_lines(obj, indent=2):
@@ -542,19 +575,19 @@ def run(self):
                 self.BUILD_DIR,
                 f'{self.NAME}=={self.VERSION}',
             ]
-            check_call(cmd)
+            run(cmd)
 
         else:
             # Run sdist or bdist_wheel to make a source tarball or wheel in the recipe
             # dir:
-            cmd = [sys.executable, 'setup.py']
+            cmd = [sys.executable, *setup_py('.')]
             if self.from_wheel:
                 cmd += ['bdist_wheel']
             else:
                 cmd += ['sdist', '--formats=gztar']
             cmd += ['--dist-dir=' + self.BUILD_DIR]
 
-        check_call(cmd)
+        run(cmd)
 
         if self.from_wheel or self.from_downloaded_wheel:
             dist = [p for p in os.listdir(self.BUILD_DIR) if p.endswith('.whl')][0]
@@ -627,7 +660,7 @@ def run(self):
 
         environ = os.environ.copy()
         environ['CONDA_BLD_PATH'] = os.path.abspath(self.CONDA_BLD_PATH)
-        check_call(
+        run(
             ['conda-build', '--no-test', self.RECIPE_DIR] + channel_args, env=environ,
         )