slightly modified stringsWithDeps script Builder proposal adding the feature

overriding steps and has better documentation (IMHO) reusing as much as
possible of the code already written by raskin

svn path=/nixpkgs/trunk/; revision=10225

1 files changed, 47 insertions, 0 deletions

diff --git a/pkgs/lib/strings-with-deps2.nix b/pkgs/lib/strings-with-deps2.nix
new file mode 100644
index 000000000000..85c3526ee22a
--- /dev/null
+++ b/pkgs/lib/strings-with-deps2.nix
@@ -0,0 +1,47 @@
+/* propoal Marc Weber (original idea and implementation: Michael Raskin)
+  This should not be a complete rewrite of Michael Raskins code.
+  I only fear having to override one step.. 
+  (which could be done using textClosureMap = f: .. and telling f to substitute a text string)
+  But I don't like this solution
+
+  I've rewritten the part creating the actual step hoping that it's easier to understand.
+
+  Baisc idea keeps the same: assemble a custom builder script by concatenating
+  text snippets with dependencies.
+
+  Difference: Instead of concatenating the text snippets only aliases are concatenated [1]
+  Then those alias names are looked up from an attribute set [2]
+  (this way giving you full control overriding steps)
+
+  All script snippets written by Michael Raskin will be reused thankfully :)
+*/
+ 
+/* Example:
+setup = { 
+  name = "setup";
+  value = "echo setup";       # the text snippet (by calling it value it fits the attr name expected by listToAttrs 
+}
+ 
+unpack = { 
+  name = "unpack";
+  value = "tar xf ... ";
+  dependencies = [ "setup" ]; # createScript ensures that these are prependend to this text snipped
+}
+
+script = createScript { steps = [setup unpack] }
+is equal to
+script = createScript { steps = [unpack] }
+
+# overriding example:
+script_overridden_setup = createScript { steps = [unpack]; override = { setup = "overridden setup"; }; };
+*/
+lib :
+let inherit (builtins) listToAttrs; 
+    inherit (lib) intersperse concatLists uniqList concatStrings;
+    in {
+     createScript = { steps, override ? {} } : let 
+        addNameToDeps = r : ( if (r ? dependencies) then r.dependencies else [] ) ++ [r.name];
+        names = uniqList { inputList = concatLists ( map addNameToDeps steps ) ; }; # [1] 
+        scriptsAsAttrs = listToAttrs steps; # [2] 
+      in concatStrings ( intersperse "\n" (map (x : __getAttr x (scriptsAsAttrs // override ) ) names) );
+    }