From 95d2a3227bcc8a589ad2a908dc1f94b605fc8cca Mon Sep 17 00:00:00 2001
From: Doron Behar <doron.behar@gmail.com>
Date: Mon, 22 Jun 2026 14:47:48 +0300
Subject: [PATCH] python3Packages.numpy: make numpy.pc more visible

This change also enables scipy to find numpy via pkg-config, and not
only via `scipy.passthru.buildConfig.properties.numpy-include-dir`, and
thus enables free threading via f2py. See:

https://github.com/scipy/scipy/commit/7fd20c742b74264e7c75e86292b7b8748a63d53c#diff-b39b7bda5a39c101be8d9e0b3b6d4da335b6daf7385c2a43463125b0a1f33778

Arguably, this makes the `numpy.passthru.coreIncludeDir` definition
redundant, but we will keep it for backwards compatibility.
---
 pkgs/development/python-modules/numpy/2.nix | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/python-modules/numpy/2.nix b/pkgs/development/python-modules/numpy/2.nix
index 1a5eaecaa010..6849c82285c0 100644
--- a/pkgs/development/python-modules/numpy/2.nix
+++ b/pkgs/development/python-modules/numpy/2.nix
@@ -113,6 +113,14 @@ buildPythonPackage (finalAttrs: {
     typing-extensions
   ];
 
+  # Enables any dependent package to easily find numpy.pc via standard
+  # pkg-config call. The `$out/include` symlink matches what's written in the
+  # numpy.pc file.
+  postInstall = ''
+    ln -s $out/${python.sitePackages}/numpy/_core/lib/pkgconfig $out/lib/pkgconfig
+    ln -s ${placeholder "out"}/${finalAttrs.passthru.coreIncludeInnerDir} $out/include
+  '';
+
   preCheck = ''
     pushd $out
     # For numpy-config executable to be available during tests
@@ -192,7 +200,11 @@ buildPythonPackage (finalAttrs: {
       name = "site.cfg";
       text = lib.generators.toINI { } finalAttrs.finalPackage.buildConfig;
     };
-    coreIncludeDir = "${finalAttrs.finalPackage}/${python.sitePackages}/numpy/_core/include";
+    # Need to be defined with two variables for postInstall to use `placeholder
+    # "out"` where here we have to use `${finalAttrs.finalPackage}`, that would
+    # cause infinite recursion if used in postInstall too.
+    coreIncludeInnerDir = "${python.sitePackages}/numpy/_core/include";
+    coreIncludeDir = "${finalAttrs.finalPackage}/${finalAttrs.finalPackage.passthru.coreIncludeInnerDir}";
     tests = {
       inherit sage;
     };