lib: re-export missing pure builtins in lib (#483020)

lib/default.nix

@@ -105,6 +105,9 @@ let
       # network
       network = callLibs ./network;
 
+      # flakes
+      flakes = callLibs ./flakes.nix;
+
       inherit (builtins)
         getContext
         hasContext
@@ -390,6 +393,8 @@ let
         toInt
         toIntBase10
         fileContents
+        appendContext
+        unsafeDiscardStringContext
         ;
       inherit (self.stringsWithDeps)
         textClosureList
@@ -414,7 +419,13 @@ let
         renameCrossIndexTo
         mapCrossIndex
         ;
-      inherit (self.derivations) lazyDerivation optionalDrvAttr warnOnInstantiate;
+      inherit (self.derivations)
+        lazyDerivation
+        optionalDrvAttr
+        warnOnInstantiate
+        addDrvOutputDependencies
+        unsafeDiscardOutputDependency
+        ;
       inherit (self.generators) mkLuaInline;
       inherit (self.meta)
         addMetaAttrs
@@ -442,6 +453,9 @@ let
         dirOf
         isPath
         packagesFromDirectoryRecursive
+        hashFile
+        readDir
+        readFileType
         ;
       inherit (self.sources)
         cleanSourceFilter
@@ -592,6 +606,10 @@ let
       inherit (self.network.ipv6)
         mkEUI64Suffix
         ;
+      inherit (self.flakes)
+        parseFlakeRef
+        flakeRefToString
+        ;
     }
   );
 in

lib/derivations.nix

@@ -21,6 +21,11 @@ let
     if pkg ? meta.position && isString pkg.meta.position then "${prefix}${pkg.meta.position}" else "";
 in
 {
+  inherit (builtins)
+    addDrvOutputDependencies
+    unsafeDiscardOutputDependency
+    ;
+
   /**
     Restrict a derivation to a predictable set of attribute names, so
     that the returned attrset is not strict in the actual derivation,

lib/filesystem.nix

@@ -31,6 +31,12 @@ in
     isPath
     ;
 
+  inherit (builtins)
+    readDir
+    readFileType
+    hashFile
+    ;
+
   /**
     The type of a path. The path needs to exist and be accessible.
     The result is either `"directory"` for a directory, `"regular"` for a

lib/flakes.nix

@@ -0,0 +1,12 @@
+/**
+  Flake operations.
+*/
+{ lib }:
+{
+
+  inherit (builtins)
+    parseFlakeRef
+    flakeRefToString
+    ;
+
+}

lib/strings.nix

@@ -39,6 +39,7 @@ rec {
     toJSON
     typeOf
     unsafeDiscardStringContext
+    appendContext
     ;
 
   /**