chg: usr: add func to filter duplicate child docs with same prefix

* in case of duplicate child prefix, keep the one with longest path,
  which is what we want for target docs in subtree path
* add a test func and logging calls, set filter result to info

Signed-off-by: Stephen L Arnold <sarnold@vctlabs.com>

Author: sarnold

doorstop/core/tests/test_tree.py

@@ -162,6 +162,25 @@ def test_from_list_discard(self):
         self.assertEqual(2, len(tree))
         self.assertTrue(tree.validate())
 
+    def test_from_list_filter(self):
+        """Verify same prefix child is filtered."""
+        a = MockDocumentSkip(EMPTY)
+        a.prefix = "A"  # type: ignore
+        b = MockDocumentSkip(EMPTY)
+        b.prefix = "B"  # type: ignore
+        b.parent = "A"  # type: ignore
+        c = MockDocumentSkip(EMPTY)
+        c.prefix = "B"  # type: ignore
+        c.parent = "A"  # type: ignore
+        c.path = c.path + "/cempty"  # type: ignore
+        docs = [a, b, c]
+        tree = Tree.from_list(docs)
+        self.assertEqual(2, len(tree))
+        self.assertTrue(tree.validate())
+        self.assertIn('/cempty', tree.children[0].document.path)
+        #print(tree)
+        #print(tree.children)
+
     def test_from_list_no_root(self):
         """Verify an error occurs when the tree has no root."""
         a = MockDocumentSkip(EMPTY)

doorstop/core/tree.py

@@ -41,7 +41,8 @@ class Tree(BaseValidatable):  # pylint: disable=R0902
 
     @staticmethod
     def from_list(documents, root=None):
-        """Initialize a new tree from a list of documents.
+        """
+        Initialize a new tree from a list of documents.
 
         :param documents: list of :class:`~doorstop.core.document.Document`
         :param root: path to root of the project
@@ -50,8 +51,28 @@ def from_list(documents, root=None):
             cannot be built
 
         :return: new :class:`~doorstop.core.tree.Tree`
-
         """
+
+        def _filter_children_by_prefix(docs_from: List) -> List:
+            """
+            If child documents are found, filter them by document prefix
+            and only keep the document with longer path when a duplicate
+            prefix is found.
+
+            :param documents: list of :class:`~doorstop.core.document.Document`
+            :return: filtered list of :class:`~doorstop.core.document.Document`
+            """
+            seen: Dict = {}
+            for doc in docs_from:
+                if doc.prefix in seen and len(doc.path) > len(seen[doc.prefix].path):
+                    log.info("filtered from tree: {}".format(seen[doc.prefix]))
+                    seen[doc.prefix] = doc  # update previous doc, or
+                if doc.prefix not in seen:
+                    seen.update({doc.prefix: doc})  # add new doc
+            log.info("filtered result: {}".format(seen))
+            return list(seen.values())
+
+
         if not documents:
             return Tree(document=None, root=root)
         unplaced = list(documents)
@@ -65,6 +86,8 @@ def from_list(documents, root=None):
         else:
             raise DoorstopError("no root document")
 
+        unplaced = _filter_children_by_prefix(unplaced)
+
         while unplaced:
             count = len(unplaced)
             for document in list(unplaced):