From 509311147f39ba33db516e8c24191b9d7f4c1c4b Mon Sep 17 00:00:00 2001
From: Thor Whalen <1906276+thorwhalen@users.noreply.github.com>
Date: Tue, 22 Sep 2026 15:30:15 +0000
Subject: [PATCH] fix: treat i2's NotSet signature default as "no default"

`get_root_values` ignores NotSet defaults (falls back on the annotation's
default value or 0.0, as for a param with no default), and
`_compute_node_value` no longer skips a missing NotSet-defaulted param as
if it had a default. So a DAG built from signatures with NotSet defaults
(as a re-landed i2mint/i2#88 FuncFactory would show) never seeds a widget
with the sentinel. No-op for current signatures.

Uses `i2.is_not_set` when available, else falls back on `i2.deco.NotSet`.

Refs i2mint/i2#48

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 dagapp/tests/test_not_set_defaults.py | 29 +++++++++++++++++++++++++++
 dagapp/utils.py                       | 29 ++++++++++++++++++++++++---
 2 files changed, 55 insertions(+), 3 deletions(-)
 create mode 100644 dagapp/tests/test_not_set_defaults.py

diff --git a/dagapp/tests/test_not_set_defaults.py b/dagapp/tests/test_not_set_defaults.py
new file mode 100644
index 0000000..e75ac69
--- /dev/null
+++ b/dagapp/tests/test_not_set_defaults.py
@@ -0,0 +1,29 @@
+"""``i2``'s ``NotSet`` sentinel in a signature means "required / no default".
+
+See i2mint/i2#48: once ``i2.FuncFactory`` shows ``NotSet`` defaults, a DAG root with
+such a default must get the same initial value as one with no default at all.
+These tests use ``i2.deco.NotSet`` directly, so they pass with any i2 version.
+"""
+
+from i2.deco import NotSet
+from meshed import DAG
+
+from dagapp.utils import get_root_values
+
+
+def f(a: int, b, c: float = 2.0):
+    return a + b + c
+
+
+# ``f`` with ``NotSet`` defaults, as a re-landed i2#88 ``FuncFactory`` would show.
+def f_with_not_set(a: int = NotSet, b=NotSet, c: float = 2.0):
+    return a + b + c
+
+
+f_with_not_set.__name__ = f.__name__
+
+
+def test_root_values_ignore_not_set():
+    got = get_root_values(DAG([f_with_not_set]))
+    assert NotSet not in got.values()
+    assert got == get_root_values(DAG([f]))
diff --git a/dagapp/utils.py b/dagapp/utils.py
index 05b4731..03ca4e0 100644
--- a/dagapp/utils.py
+++ b/dagapp/utils.py
@@ -10,6 +10,27 @@
 import inspect
 from inspect import Parameter
 
+try:
+    from i2 import is_not_set
+except ImportError:  # older i2: same sentinel, not exported from the root yet
+    from i2.deco import NotSet as _NotSet
+
+    def is_not_set(x) -> bool:
+        """Return True iff ``x`` is ``i2``'s ``NotSet`` sentinel."""
+        return x is _NotSet
+
+
+def _has_default(param: Parameter) -> bool:
+    """True iff ``param`` has a real default (``i2``'s ``NotSet`` doesn't count).
+
+    >>> from i2.deco import NotSet
+    >>> [_has_default(Parameter('x', Parameter.KEYWORD_ONLY, default=d))
+    ...  for d in (None, 0, NotSet, Parameter.empty)]
+    [True, True, False, False]
+    """
+    return param.default is not Parameter.empty and not is_not_set(param.default)
+
+
 DFLT_VALS = {
     int: 0,
     float: 0.0,
@@ -281,7 +302,7 @@ def _compute_node_value(node, funcs):
         # If the parameter isn't present in session state but has a default,
         # omit it so the function can use its default value.
         if name not in st.session_state:
-            if param.default is not inspect._empty:
+            if _has_default(param):
                 continue
             # preserve previous behaviour: accessing missing keys will raise
             # the same KeyError as before
@@ -309,9 +330,11 @@ def get_root_values(dag):
     Returns the default values for all the root nodes found in dag
     """
     root_defaults = dict()
+    # i2's NotSet sentinel means "no default": fall back on the annotation or 0.0
+    defaults = {k: v for k, v in dag.sig.defaults.items() if not is_not_set(v)}
     for name in dag.sig.names:
-        if name in dag.sig.defaults:
-            dflt = dag.sig.defaults[name]
+        if name in defaults:
+            dflt = defaults[name]
             if dflt is not None:
                 root_defaults[name] = dflt
         elif name in dag.sig.annotations: