Platform normalization

lib/attrsets.nix

@@ -2,7 +2,7 @@
 
 let
   inherit (builtins) head tail length;
-  inherit (import ./trivial.nix) or;
+  inherit (import ./trivial.nix) and or;
   inherit (import ./default.nix) fold;
   inherit (import ./strings.nix) concatStringsSep;
   inherit (import ./lists.nix) concatMap concatLists all deepSeqList;
@@ -417,18 +417,15 @@ rec {
 
   /* Returns true if the pattern is contained in the set. False otherwise.
 
-     FIXME(zimbatm): this example doesn't work !!!
-
      Example:
-       sys = mkSystem { }
-       matchAttrs { cpu = { bits = 64; }; } sys
+       matchAttrs { cpu = {}; } { cpu = { bits = 64; }; }
        => true
    */
-  matchAttrs = pattern: attrs:
-    fold or false (attrValues (zipAttrsWithNames (attrNames pattern) (n: values:
+  matchAttrs = pattern: attrs: assert isAttrs pattern;
+    fold and true (attrValues (zipAttrsWithNames (attrNames pattern) (n: values:
       let pat = head values; val = head (tail values); in
       if length values == 1 then false
-      else if isAttrs pat then isAttrs val && matchAttrs head values
+      else if isAttrs pat then isAttrs val && matchAttrs pat val
       else pat == val
     ) [pattern attrs]));
 

lib/default.nix

@@ -22,8 +22,7 @@ let
 
   # constants
   licenses = import ./licenses.nix;
-  platforms = import ./platforms.nix;
-  systems = import ./systems.nix;
+  systems = import ./systems;
 
   # misc
   debug = import ./debug.nix;
@@ -42,13 +41,15 @@ in
             attrsets lists strings stringsWithDeps
             customisation maintainers meta sources
             modules options types
-            licenses platforms systems
+            licenses systems
             debug generators misc
             sandbox fetchers filesystem;
+
+    # back-compat aliases
+    platforms = systems.doubles;
   }
   # !!! don't include everything at top-level; perhaps only the most
   # commonly used functions.
   // trivial // lists // strings // stringsWithDeps // attrsets // sources
   // options // types // meta // debug // misc // modules
-  // systems
   // customisation

lib/systems/default.nix

@@ -0,0 +1,23 @@
+rec {
+  doubles = import ./doubles.nix;
+  parse = import ./parse.nix;
+  platforms = import ./platforms.nix;
+
+  # Elaborate a `localSystem` or `crossSystem` so that it contains everything
+  # necessary.
+  #
+  # `parsed` is inferred from args, both because there are two options with one
+  # clearly prefered, and to prevent cycles. A simpler fixed point where the RHS
+  # always just used `final.*` would fail on both counts.
+  elaborate = args: let
+    final = {
+      # Prefer to parse `config` as it is strictly more informative.
+      parsed = parse.mkSystemFromString (if args ? config then args.config else args.system);
+      # Either of these can be losslessly-extracted from `parsed` iff parsing succeeds.
+      system = parse.doubleFromSystem final.parsed;
+      config = parse.tripleFromSystem final.parsed;
+      # Just a guess, based on `system`
+      platform = platforms.selectBySystem final.system;
+    } // args;
+  in final;
+}

lib/systems/doubles.nix

@@ -0,0 +1,44 @@
+let lists = import ../lists.nix; in
+let parse = import ./parse.nix; in
+let inherit (import ../attrsets.nix) matchAttrs; in
+
+let
+  all = [
+    "aarch64-linux"
+    "armv5tel-linux" "armv6l-linux" "armv7l-linux"
+
+    "mips64el-linux"
+
+    "i686-cygwin" "i686-freebsd" "i686-linux" "i686-netbsd" "i686-openbsd"
+
+    "x86_64-cygwin" "x86_64-darwin" "x86_64-freebsd" "x86_64-linux"
+    "x86_64-netbsd" "x86_64-openbsd" "x86_64-solaris"
+  ];
+
+  allParsed = map parse.mkSystemFromString all;
+
+  filterDoubles = f: map parse.doubleFromSystem (lists.filter f allParsed);
+
+in rec {
+  inherit all;
+
+  allBut = platforms: lists.filter (x: !(builtins.elem x platforms)) all;
+  none = [];
+
+  arm = filterDoubles (matchAttrs { cpu = { family = "arm"; bits = 32; }; });
+  i686 = filterDoubles parse.isi686;
+  mips = filterDoubles (matchAttrs { cpu = { family = "mips"; }; });
+  x86_64 = filterDoubles parse.isx86_64;
+
+  cygwin = filterDoubles (matchAttrs { kernel = parse.kernels.cygwin; });
+  darwin = filterDoubles parse.isDarwin;
+  freebsd = filterDoubles (matchAttrs { kernel = parse.kernels.freebsd; });
+  gnu = filterDoubles (matchAttrs { kernel = parse.kernels.linux; abi = parse.abis.gnu; }); # Should be better
+  illumos = filterDoubles (matchAttrs { kernel = parse.kernels.solaris; });
+  linux = filterDoubles parse.isLinux;
+  netbsd = filterDoubles (matchAttrs { kernel = parse.kernels.netbsd; });
+  openbsd = filterDoubles (matchAttrs { kernel = parse.kernels.openbsd; });
+  unix = filterDoubles parse.isUnix;
+
+  mesaPlatforms = ["i686-linux" "x86_64-linux" "x86_64-darwin" "armv5tel-linux" "armv6l-linux" "armv7l-linux" "aarch64-linux"];
+}