Use prop_filter to force directory treenode.

Signed-off-by: Christian Hagemeier <[email protected]>

mountpoint-s3/tests/reftests/generators.rs

@@ -127,21 +127,21 @@ impl Debug for TreeNode {
 /// Leaves are always [TreeNode::File] or an empty [TreeNode::Directory].
 /// Parents are always [TreeNode::Directory].
 pub fn gen_tree(depth: u32, max_size: u32, max_items: u32, max_width: usize) -> impl Strategy<Value = TreeNode> {
-    let leaf = any::<FileContent>().prop_map(TreeNode::File);
-
-    let strategy = leaf.prop_recursive(
+    let leaf = prop_oneof![any::<FileContent>().prop_map(TreeNode::File),];
+    leaf.prop_recursive(
         depth,     // levels
         max_size,  // max number of nodes
         max_items, // number of items per collection
         move |inner| {
-            // Take the inner strategy and make the recursive cases.
-            // Since the size of the tree could be zero, this also introduces directories as leaves.
-            prop::collection::btree_map(any::<Name>(), inner, 0..max_width).prop_map(TreeNode::Directory)
+            prop_oneof![
+                // Take the inner strategy and make the recursive cases.
+                prop::collection::btree_map(any::<Name>(), inner, 0..max_width).prop_map(TreeNode::Directory),
+            ]
         },
-    );
-
-    // Ensure the root is always a directory by wrapping the inner strategy
-    prop::collection::btree_map(any::<Name>(), strategy, 0..max_width).prop_map(TreeNode::Directory)
+    ).prop_filter(
+        "Root must be a directory",
+        |tree| matches!(tree, TreeNode::Directory(_))
+    )
 }
 
 /// Take a generated tree and create the corresponding S3 namespace (list of keys)