From cd227857256b2e6bbc98969956fd290b505eff71 Mon Sep 17 00:00:00 2001
From: Rich FitzJohn <r.fitzjohn@imperial.ac.uk>
Date: Mon, 7 Aug 2023 15:57:35 +0100
Subject: [PATCH] Add utility to test actions

---
 src/outpack/util.py | 14 ++++++++++++++
 tests/test_util.py  |  8 ++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 src/outpack/util.py
 create mode 100644 tests/test_util.py

diff --git a/src/outpack/util.py b/src/outpack/util.py
new file mode 100644
index 0000000..735e9fe
--- /dev/null
+++ b/src/outpack/util.py
@@ -0,0 +1,14 @@
+from pathlib import Path
+
+
+def find_file_descend(filename, path):
+    path = Path(path)
+    root = Path(path.root)
+
+    while path != root:
+        attempt = path / filename
+        if attempt.exists():
+            return str(attempt.parent)
+        path = path.parent
+
+    return None
diff --git a/tests/test_util.py b/tests/test_util.py
new file mode 100644
index 0000000..6f7c6f1
--- /dev/null
+++ b/tests/test_util.py
@@ -0,0 +1,8 @@
+from outpack.util import find_file_descend
+
+
+def test_find_descend(tmp_path):
+    (tmp_path / "a" / "b" / "c" / "d").mkdir(parents=True)
+    (tmp_path / "a" / "b" / ".foo").mkdir(parents=True)
+    assert find_file_descend(".foo", tmp_path / "a/b/c/d") == str(tmp_path / "a/b")
+    assert find_file_descend(".foo", tmp_path / "a") is None