Move pkgs/lib/ to lib/

1 files changed, 329 insertions, 0 deletions

diff --git a/lib/attrsets.nix b/lib/attrsets.nix
new file mode 100644
index 00000000000..01d51779c80
--- /dev/null
+++ b/lib/attrsets.nix
@@ -0,0 +1,329 @@
+# Operations on attribute sets.
+
+with {
+  inherit (builtins) head tail isString;
+  inherit (import ./trivial.nix) or;
+  inherit (import ./default.nix) fold;
+  inherit (import ./strings.nix) concatStringsSep;
+  inherit (import ./lists.nix) concatMap concatLists all deepSeqList;
+  inherit (import ./misc.nix) maybeAttr;
+};
+
+rec {
+  inherit (builtins) attrNames listToAttrs hasAttr isAttrs getAttr;
+
+
+  /* Return an attribute from nested attribute sets.  For instance
+     ["x" "y"] applied to some set e returns e.x.y, if it exists.  The
+     default value is returned otherwise. */
+  attrByPath = attrPath: default: e:
+    let attr = head attrPath;
+    in
+      if attrPath == [] then e
+      else if builtins ? hasAttr && hasAttr attr e
+      then attrByPath (tail attrPath) default (getAttr attr e)
+      else default;
+
+
+  /* Return nested attribute set in which an attribute is set.  For instance
+     ["x" "y"] applied with some value v returns `x.y = v;' */
+  setAttrByPath = attrPath: value:
+    if attrPath == [] then value
+    else listToAttrs [(
+      nameValuePair (head attrPath) (setAttrByPath (tail attrPath) value)
+    )];
+
+
+  getAttrFromPath = attrPath: set:
+    let errorMsg = "cannot find attribute `" + concatStringsSep "." attrPath + "'";
+    in attrByPath attrPath (abort errorMsg) set;
+
+
+  /* Return the specified attributes from a set.
+
+     Example:
+       attrVals ["a" "b" "c"] as
+       => [as.a as.b as.c]
+  */
+  attrVals = nameList: set:
+    map (x: getAttr x set) nameList;
+
+
+  /* Return the values of all attributes in the given set, sorted by
+     attribute name.
+
+     Example:
+       attrValues {c = 3; a = 1; b = 2;}
+       => [1 2 3]
+  */
+  attrValues = attrs: attrVals (attrNames attrs) attrs;
+
+
+  /* Collect each attribute named `attr' from a list of attribute
+     sets.  Sets that don't contain the named attribute are ignored.
+
+     Example:
+       catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}]
+       => [1 2]
+  */
+  catAttrs = attr: l: concatLists (map (s: if hasAttr attr s then [(getAttr attr s)] else []) l);
+
+
+  /* Filter an attribute set by removing all attributes for which the
+     given predicate return false.
+
+     Example:
+       filterAttrs (n: v: n == "foo") { foo = 1; bar = 2; }
+       => { foo = 1; }
+  */
+  filterAttrs = pred: set:
+    listToAttrs (fold (n: ys: let v = getAttr n set; in if pred n v then [(nameValuePair n v)] ++ ys else ys) [] (attrNames set));
+
+
+  /* foldAttrs: apply fold functions to values grouped by key. Eg accumulate values as list:
+     foldAttrs (n: a: [n] ++ a) [] [{ a = 2; } { a = 3; }]
+     => { a = [ 2 3 ]; }
+  */
+  foldAttrs = op: nul: list_of_attrs:
+    fold (n: a:
+        fold (name: o:
+          o // (listToAttrs [{inherit name; value = op (getAttr name n) (maybeAttr name nul a); }])
+        ) a (attrNames n)
+    ) {} list_of_attrs;
+
+
+  /* Recursively collect sets that verify a given predicate named `pred'
+     from the set `attrs'.  The recursion is stopped when the predicate is
+     verified.
+
+     Type:
+       collect ::
+         (AttrSet -> Bool) -> AttrSet -> AttrSet
+
+     Example:
+       collect builtins.isList { a = { b = ["b"]; }; c = [1]; }
+       => [["b"] [1]]
+
+       collect (x: x ? outPath)
+          { a = { outPath = "a/"; }; b = { outPath = "b/"; }; }
+       => [{ outPath = "a/"; } { outPath = "b/"; }]
+  */
+  collect = pred: attrs:
+    if pred attrs then
+      [ attrs ]
+    else if builtins.isAttrs attrs then
+      concatMap (collect pred) (attrValues attrs)
+    else
+      [];
+
+
+  /* Utility function that creates a {name, value} pair as expected by
+     builtins.listToAttrs. */
+  nameValuePair = name: value: { inherit name value; };
+
+
+  /* Apply a function to each element in an attribute set.  The
+     function takes two arguments --- the attribute name and its value
+     --- and returns the new value for the attribute.  The result is a
+     new attribute set.
+
+     Example:
+       mapAttrs (name: value: name + "-" + value)
+          { x = "foo"; y = "bar"; }
+       => { x = "x-foo"; y = "y-bar"; }
+  */
+  mapAttrs = f: set:
+    listToAttrs (map (attr: nameValuePair attr (f attr (getAttr attr set))) (attrNames set));
+
+
+  /* Like `mapAttrs', but allows the name of each attribute to be
+     changed in addition to the value.  The applied function should
+     return both the new name and value as a `nameValuePair'.
+
+     Example:
+       mapAttrs' (name: value: nameValuePair ("foo_" + name) ("bar-" + value))
+          { x = "a"; y = "b"; }
+       => { foo_x = "bar-a"; foo_y = "bar-b"; }
+  */
+  mapAttrs' = f: set:
+    listToAttrs (map (attr: f attr (getAttr attr set)) (attrNames set));
+
+
+  /* Call a function for each attribute in the given set and return
+     the result in a list.
+
+     Example:
+       mapAttrsToList (name: value: name + value)
+          { x = "a"; y = "b"; }
+       => [ "xa" "yb" ]
+  */
+  mapAttrsToList = f: attrs:
+    map (name: f name (getAttr name attrs)) (attrNames attrs);
+
+
+  /* Like `mapAttrs', except that it recursively applies itself to
+     attribute sets.  Also, the first argument of the argument
+     function is a *list* of the names of the containing attributes.
+
+     Type:
+       mapAttrsRecursive ::
+         ([String] -> a -> b) -> AttrSet -> AttrSet
+
+     Example:
+       mapAttrsRecursive (path: value: concatStringsSep "-" (path ++ [value]))
+         { n = { a = "A"; m = { b = "B"; c = "C"; }; }; d = "D"; }
+       => { n = { a = "n-a-A"; m = { b = "n-m-b-B"; c = "n-m-c-C"; }; }; d = "d-D"; }
+  */
+  mapAttrsRecursive = mapAttrsRecursiveCond (as: true);
+
+
+  /* Like `mapAttrsRecursive', but it takes an additional predicate
+     function that tells it whether to recursive into an attribute
+     set.  If it returns false, `mapAttrsRecursiveCond' does not
+     recurse, but does apply the map function.  It is returns true, it
+     does recurse, and does not apply the map function.
+
+     Type:
+       mapAttrsRecursiveCond ::
+         (AttrSet -> Bool) -> ([String] -> a -> b) -> AttrSet -> AttrSet
+
+     Example:
+       # To prevent recursing into derivations (which are attribute
+       # sets with the attribute "type" equal to "derivation"):
+       mapAttrsRecursiveCond
+         (as: !(as ? "type" && as.type == "derivation"))
+         (x: ... do something ...)
+         attrs
+  */
+  mapAttrsRecursiveCond = cond: f: set:
+    let
+      recurse = path: set:
+        let
+          g =
+            name: value:
+            if isAttrs value && cond value
+              then recurse (path ++ [name]) value
+              else f (path ++ [name]) value;
+        in mapAttrs g set;
+    in recurse [] set;
+
+
+  /* Generate an attribute set by mapping a function over a list of
+     attribute names.
+
+     Example:
+       genAttrs [ "foo" "bar" ] (name: "x_" + name)
+       => { foo = "x_foo"; bar = "x_bar"; }
+  */
+  genAttrs = names: f:
+    listToAttrs (map (n: nameValuePair n (f n)) names);
+
+
+  /* Check whether the argument is a derivation. */
+  isDerivation = x: isAttrs x && x ? type && x.type == "derivation";
+
+
+  /* If the Boolean `cond' is true, return the attribute set `as',
+     otherwise an empty attribute set. */
+  optionalAttrs = cond: as: if cond then as else {};
+
+
+  /* Merge sets of attributes and use the function f to merge attributes
+     values. */
+  zipAttrsWithNames = names: f: sets:
+    listToAttrs (map (name: {
+      inherit name;
+      value = f name (catAttrs name sets);
+    }) names);
+
+  # implentation note: Common names  appear multiple times in the list of
+  # names, hopefully this does not affect the system because the maximal
+  # laziness avoid computing twice the same expression and listToAttrs does
+  # not care about duplicated attribute names.
+  zipAttrsWith = f: sets: zipWithNames (concatMap attrNames sets) f sets;
+
+  zipAttrs = zipAttrsWith (name: values: values);
+
+  /* backward compatibility */
+  zipWithNames = zipAttrsWithNames;
+  zip = builtins.trace "lib.zip is deprecated, use lib.zipAttrsWith instead" zipAttrsWith;
+
+
+  /* Does the same as the update operator '//' except that attributes are
+     merged until the given pedicate is verified.  The predicate should
+     accept 3 arguments which are the path to reach the attribute, a part of
+     the first attribute set and a part of the second attribute set.  When
+     the predicate is verified, the value of the first attribute set is
+     replaced by the value of the second attribute set.
+
+     Example:
+       recursiveUpdateUntil (path: l: r: path == ["foo"]) {
+         # first attribute set
+         foo.bar = 1;
+         foo.baz = 2;
+         bar = 3;
+       } {
+         #second attribute set
+         foo.bar = 1;
+         foo.quz = 2;
+         baz = 4;
+       }
+
+       returns: {
+         foo.bar = 1; # 'foo.*' from the second set
+         foo.quz = 2; #
+         bar = 3;     # 'bar' from the first set
+         baz = 4;     # 'baz' from the second set
+       }
+
+     */
+  recursiveUpdateUntil = pred: lhs: rhs:
+    let f = attrPath:
+      zipAttrsWith (n: values:
+        if tail values == []
+        || pred attrPath (head (tail values)) (head values) then
+          head values
+        else
+          f (attrPath ++ [n]) values
+      );
+    in f [] [rhs lhs];
+
+  /* A recursive variant of the update operator ‘//’.  The recusion
+     stops when one of the attribute values is not an attribute set,
+     in which case the right hand side value takes precedence over the
+     left hand side value.
+
+     Example:
+       recursiveUpdate {
+         boot.loader.grub.enable = true;
+         boot.loader.grub.device = "/dev/hda";
+       } {
+         boot.loader.grub.device = "";
+       }
+
+       returns: {
+         boot.loader.grub.enable = true;
+         boot.loader.grub.device = "";
+       }
+
+     */
+  recursiveUpdate = lhs: rhs:
+    recursiveUpdateUntil (path: lhs: rhs:
+      !(isAttrs lhs && isAttrs rhs)
+    ) lhs rhs;
+
+  matchAttrs = pattern: attrs:
+    fold or false (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 pat == val
+    ) [pattern attrs]));
+
+  # override only the attributes that are already present in the old set
+  # useful for deep-overriding
+  overrideExisting = old: new:
+    old // listToAttrs (map (attr: nameValuePair attr (attrByPath [attr] (getAttr attr old) new)) (attrNames old));
+
+  deepSeqAttrs = x: y: deepSeqList (attrValues x) y;
+}