ENH: improvements to pythran-config for build system integration

xref issue 2257

.github/workflows/no-setuptools.yml

@@ -27,6 +27,9 @@ jobs:
       run: |
         python -m pip install .
         python -m pip uninstall -y setuptools  # the goal of that check is to test codegen without setuptools
+    - name: Testing pythran-config
+      run: |
+        pythran-config --cflags-pythran-only
     - name: Testing scipy
       run: |
         find pythran/tests/scipy/ -name '*.py' -exec pythran -E {} \;

pythran/config.py

@@ -308,10 +308,7 @@ def run():
     Dump on stdout the config flags required to compile pythran-generated code.
     '''
     import argparse
-    import distutils.ccompiler
-    import distutils.sysconfig
     import pythran
-    import numpy
 
     parser = argparse.ArgumentParser(
         prog='pythran-config',
@@ -323,7 +320,24 @@ def run():
                         help='print default compiler')
 
     parser.add_argument('--cflags', action='store_true',
-                        help='print compilation flags')
+                        help='print compilation flags to compile extension '
+                             'modules directly')
+
+    # The with-BLAS variant could be added if there's user demand. Unclear
+    # if there are packages that need this, and also integrate with a build
+    # system for Python and NumPy flags. SciPy and scikit-image need the
+    # no-BLAS variant.
+    parser.add_argument('--cflags-pythran-only', action='store_true',
+                        help='print compilation flags for usage by a build '
+                             'system (doesn\'t include Python, NumPy or BLAS '
+                             'flags).'
+                        )
+
+    parser.add_argument('--include-dir', action='store_true',
+                        help=(
+                            'print Pythran include directory '
+                            '(matches `pythran.get_include()`).')
+                        )
 
     parser.add_argument('--libs', action='store_true',
                         help='print linker flags')
@@ -344,6 +358,26 @@ def run():
 
     args = parser.parse_args(sys.argv[1:])
 
+    # This should not rely on distutils/setuptools, or anything else not in the
+    # stdlib. Please don't add imports higher up.
+    if args.cflags_pythran_only:
+        if args.cflags:
+            print("Error: --cflags and --cflags-pythran-only are mutually "
+                  "exclusive, please use only one.")
+
+        compile_flags = [
+                "-D__PYTHRAN__=3",
+                "-DENABLE_PYTHON_MODULE",
+                "-DPYTHRAN_BLAS_NONE",
+                ]
+        print(" ".join(compile_flags), f"-I{get_include()}")
+        return None
+
+
+    import distutils.ccompiler
+    import distutils.sysconfig
+    import numpy
+
     args.python = not args.no_python
 
     output = []
@@ -411,6 +445,9 @@ def fmt_define(define):
         if args.libs:
             output.extend(ldflags)
 
+    if args.include_dir:
+        output.append(get_include())
+
     if output:
         print(' '.join(output))