setup-hooks: add auto-patch-pc-hook

doc/hooks/autoPatchPkgConfigHook.section.md

@@ -0,0 +1,12 @@
+# autoPatchPkgConfigHook {#auto-patch-pkg-config-hook}
+
+The `autoPatchPkgConfigHook` hook replaces all packages listed in `Requires` and
+`Requires.private` fields with absolute paths to their pkg-config files. This
+effectively means that dependency resolution by `pkg-config` is moved from the
+build phase of the dependent package to the build phase of the dependency which
+is important since the dependent package may not be aware of its transitive
+dependencies.
+
+You should use this hook if your package produces pkg-config files with
+non-empty `Requires` or `Requires.private` fields. To use it simply add it to
+the `nativeBuildInputs`.

doc/hooks/index.md

@@ -36,6 +36,7 @@ tauri.section.md
 tetex-tex-live.section.md
 unzip.section.md
 validatePkgConfig.section.md
+autoPatchPkgConfigHook.section.md
 versionCheckHook.section.md
 waf.section.md
 zig.section.md

doc/redirects.json

@@ -1,4 +1,7 @@
 {
+  "auto-patch-pkg-config-hook": [
+    "index.html#auto-patch-pkg-config-hook"
+  ],
   "chap-build-helpers-finalAttrs": [
     "index.html#chap-build-helpers-finalAttrs"
   ],

pkgs/build-support/setup-hooks/patch-pc.py

@@ -0,0 +1,52 @@
+# Replaces dependencies in pc files with their absolute paths
+#
+# Usage: python patch-pc.py /path/to/pkgconf libfoo.pc
+# The tool writes patched .pc file to the stdout
+
+from subprocess import run
+import sys
+import re
+
+LINE_SEP = re.compile(r"(?<!\\)\n")
+
+pkgconf_bin = sys.argv[1]
+pc_file = sys.argv[2]
+
+
+def run_pkgconf(*args: str) -> str:
+    result = run([pkgconf_bin, *args], capture_output=True, check=True)
+    return result.stdout.decode().rstrip()
+
+
+def get_path(name: str) -> str:
+    return run_pkgconf("--path", name)
+
+
+def list_requires(file: str, private: bool) -> list[str]:
+    return run_pkgconf(
+        f"--print-requires{"-private" if private else ""}", file
+    ).splitlines()
+
+
+def transform_dep_spec(dep_spec: str) -> str:
+    def escape(s: str) -> str:
+        return s.replace("#", "\\#")
+
+    [name, *version_spec] = dep_spec.split(" ")
+    return " ".join(escape(s) for s in [get_path(name), *version_spec])
+
+
+def print_requires(file: str, private: bool):
+    requires = (transform_dep_spec(dep) for dep in list_requires(file, private))
+    print(f"Requires{".private" if private else ""}: ", end="")
+    print(*requires, sep=", ")
+
+
+with open(pc_file, "r") as f:
+    for line in LINE_SEP.split(f.read()):
+        if line.lstrip().startswith("Requires:"):
+            print_requires(pc_file, private=False)
+        elif line.lstrip().startswith("Requires.private:"):
+            print_requires(pc_file, private=True)
+        else:
+            print(line)

pkgs/top-level/all-packages.nix

@@ -1004,6 +1004,36 @@ with pkgs;
     ];
   } ../build-support/setup-hooks/validate-pkg-config.sh;
 
+  autoPatchPkgConfigHook =
+    makeSetupHook
+      {
+        name = "auto-patch-pkg-config-hook";
+        propagatedBuildInputs = [ pkg-config ];
+      }
+      (
+        writeScript "patch-pc.sh" ''
+          fixupOutputHooks+=(autoPatchPcHook)
+
+          autoPatchPcHook() (
+              # Some packages list their own libraries as deps, they should be searched first in case of cyclic deps
+              export PKG_CONFIG_PATH_${pkgconf.suffixSalt}="$prefix/lib/pkgconfig:$prefix/share/pkgconfig:$PKG_CONFIG_PATH_${pkgconf.suffixSalt}"
+
+              shopt -s nullglob
+              for pc in $prefix/{lib,lib64,share}/pkgconfig/*.pc; do
+                  echo Fixing require paths in $pc file
+
+                  if ! ${lib.getExe python3Minimal} \
+                    ${../build-support/setup-hooks/patch-pc.py} \
+                    ${lib.getExe pkgconf} "$pc" > "$pc.patched"; then
+                      exit 1
+                  fi
+                  mv "$pc.patched" "$pc"
+              done
+          )
+
+        ''
+      );
+
   #package writers
   writers = callPackage ../build-support/writers { };