beam: tree_root helper — portable seed path + import-time I/O guard (Q86 pattern)

wizard-work/beam/test_tree_root.py

@@ -0,0 +1,68 @@
+import os
+import sys
+import tempfile
+import pytest
+
+sys.path.insert(0, os.path.dirname(__file__))
+from tree_root import find_tree_root, assert_inside_tree, portable_seed
+
+
+def test_find_root_walks_up():
+    d = tempfile.mkdtemp()
+    root = os.path.join(d, "repo")
+    os.makedirs(os.path.join(root, "inbox"))
+    open(os.path.join(root, "WORK-QUEUE.md"), "w").write("x")
+    deep = os.path.join(root, "a", "b", "c")
+    os.makedirs(deep)
+    f = os.path.join(deep, "m.py")
+    open(f, "w").write("pass")
+    assert find_tree_root(f) == os.path.realpath(root)
+
+
+def test_find_root_missing_raises():
+    d = tempfile.mkdtemp()
+    with pytest.raises(FileNotFoundError):
+        find_tree_root(d)
+
+
+def test_assert_inside_ok():
+    root = tempfile.mkdtemp()
+    p = os.path.join(root, "inbox", "seed.json")
+    os.makedirs(os.path.dirname(p), exist_ok=True)
+    open(p, "w").write("{}")
+    assert assert_inside_tree(p, root) == os.path.realpath(p)
+
+
+def test_assert_inside_escape_raises():
+    root = tempfile.mkdtemp()
+    with pytest.raises(ValueError):
+        assert_inside_tree("/etc/passwd", root)
+
+
+def test_portable_seed_inside():
+    root = tempfile.mkdtemp()
+    os.makedirs(os.path.join(root, "inbox"))
+    p = portable_seed(root)
+    assert p.startswith(os.path.realpath(root) + os.sep)
+
+
+def test_import_no_io():
+    src = open(os.path.join(os.path.dirname(__file__), "tree_root.py")).read()
+    import builtins
+    orig = builtins.open
+    calls = []
+    def guard(*a, **k):
+        calls.append(a)
+        raise RuntimeError("import-time I/O detected")
+    ns = {}
+    builtins.open = guard
+    try:
+        try:
+            exec(compile(src, "tree_root.py", "exec"), ns)
+            assert not calls, "import-time open calls: %r" % calls
+        except RuntimeError as e:
+            if "import-time I/O" in str(e):
+                pytest.fail("module performed import-time I/O")
+            raise
+    finally:
+        builtins.open = orig

wizard-work/beam/tree_root.py

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+"""tree_root.py - derive a repo root from __file__ instead of a host-absolute path."""
+from __future__ import annotations
+
+import os
+
+
+def find_tree_root(start, marker="WORK-QUEUE.md"):
+    cur = os.path.abspath(start)
+    if os.path.isfile(cur):
+        cur = os.path.dirname(cur)
+    while True:
+        if os.path.isfile(os.path.join(cur, marker)):
+            return cur
+        parent = os.path.dirname(cur)
+        if parent == cur:
+            raise FileNotFoundError("marker %r not found in any ancestor of %s" % (marker, start))
+        cur = parent
+
+
+def assert_inside_tree(path, root):
+    rp = os.path.realpath(path)
+    rr = os.path.realpath(root)
+    if rp == rr or rp.startswith(rr + os.sep):
+        return rp
+    raise ValueError("path %s escapes tree root %s" % (rp, rr))
+
+
+def portable_seed(root, rel="inbox/seed-2026-09-26.json"):
+    return assert_inside_tree(os.path.join(root, rel), root)
+
+
+if __name__ == "__main__":
+    r = find_tree_root(__file__)
+    p = portable_seed(r)
+    print("root=", r)
+    print("seed=", p)