Versions proposal

build-support/mkgeneric/default.nix

@@ -0,0 +1,55 @@
+{ lib, config }:
+
+{
+# Intended to be an attrset of { "<exposed version>" = { version = "<full version>"; src = <path>; } }
+# or a file containing such version information
+# Type: AttrSet AttrSet
+versions,
+
+# Similar to versions, but instead contain deprecation and removal messages
+# Only added when `config.allowAliases` is true
+# This is passed the versions attr set to allow for directly referencing the version entries
+# Type: AttrSet AttrSet -> AttrSet AttrSet.
+aliases ? { ... }: { },
+
+# A "projection" from the version set to a version to be used as the default
+# Type: AttrSet package -> package
+defaultSelector,
+
+# Nix expression which takes version and package args, and returns an attrset to pass to mkDerivation
+# Type: AttrSet -> AttrSet -> AttrSet
+genericBuilder,
+}:
+
+# Some assertions as poor man's type checking
+assert builtins.isFunction defaultSelector;
+
+let
+  versionsRaw = if builtins.isPath versions then import versions else versions;
+  aliasesExpr = if builtins.isPath aliases then import aliases else aliases;
+  genericExpr = if builtins.isPath genericBuilder then import genericBuilder else genericBuilder;
+
+  aliases' = aliasesExpr { inherit lib; versions = versionsRaw; };
+  versions' = if config.allowAliases then
+      # Not sure if aliases or versions should have priority
+      versionsRaw // aliases'
+    else versionsRaw;
+
+  # This also allows for additional attrs to be passed through besides version and src
+  mkVersionArgs = { version, ... }@args: args // rec {
+    # Some helpers commonly used to determine packaging behavior
+    packageOlder = lib.versionOlder version;
+    packageAtLeast = lib.versionAtLeast version;
+    packageBetween = lower: higher: packageAtLeast lower && packageOlder higher;
+    mkVersionPassthru = packageArgs: let
+      versions = builtins.mapAttrs (_: v: mkPackage v packageArgs) versions';
+    in versions // { inherit versions; };
+  };
+
+  # Re-call the generic builder with new version args, re-wrap with makeOverridable
+  # to give it the same appearance as being called by callPackage
+  mkPackage = version: lib.makeOverridable (genericExpr (mkVersionArgs version));
+in
+  # The partially applied function doesn't need to be called with makeOverridable
+  # As callPackage will be wrapping this in makeOverridable as well
+  genericExpr (mkVersionArgs (defaultSelector versions'))

pkgs/openssl/aliases.nix

@@ -0,0 +1,9 @@
+{ lib
+, versions
+}:
+
+{
+  # Compatibility with upstream nixpkgs
+  v3 = versions.v3_0;
+  v1_0 = throw "Openssl 1.0.x is EOL, and no longer supported";
+}