fix(read-tree): Don't import `default.nix` sibling expression r/105

If a folder contains a `default.nix`, Nix expressions contained in
adjacent files should not be imported (they might be things like a
`shell.nix` or a `deps.nix` which do not evaluate to derivations).

The tree traversal still continues for all children folders of a
folder with a `default.nix`.

1 files changed, 5 insertions, 3 deletions

diff --git a/read-tree.nix b/read-tree.nix
index b2f161e885e1..2e182dfbdeef 100644
--- a/read-tree.nix
+++ b/read-tree.nix
@@ -72,10 +72,12 @@ let
     in listToAttrs (imported ++ dirs);
 
   importOr = path: dir: f:
-    let contents = f path (attrsToList dir);
+    let
+      allContents = f path (attrsToList dir);
+      dirOnlyContents = f path (filter (f: f.value == "directory") (attrsToList dir));
     in if dir ? "default.nix"
-      then import path (argsWithPath args (pathParts path)) // contents
-      else contents;
+      then import path (argsWithPath args (pathParts path)) // dirOnlyContents
+      else allContents;
 
   readTree = path: importOr path (readDir path) traverse;
 in readTree initPath