From 93bc9ce6fd99e8be9af25d53529a5d5852c50447 Mon Sep 17 00:00:00 2001
From: santhreal <64453045+santhreal@users.noreply.github.com>
Date: Tue, 14 Jul 2026 23:04:04 -0700
Subject: [PATCH] Fix get_all_foreign_keys crash sorting implicit foreign key
 targets

A foreign key that targets a table's implicit primary key has
other_column == None. When two keys to the same table were sorted, the
(other_table, column, other_column) sort key compared None to a string
and raised TypeError. Coerce the string parts to "" so the sort key is
totally ordered.
---
 datasette/utils/__init__.py | 14 ++++++++++++--
 tests/test_utils.py         | 25 +++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/datasette/utils/__init__.py b/datasette/utils/__init__.py
index 18d3ba52c9..6c9ab086b6 100644
--- a/datasette/utils/__init__.py
+++ b/datasette/utils/__init__.py
@@ -692,11 +692,21 @@ def get_all_foreign_keys(conn):
 
     # Sort foreign keys for deterministic ordering
     for table in table_to_foreign_keys:
+        # other_column is None when a foreign key targets a table's implicit
+        # primary key, so coerce to "" to keep the sort key totally ordered.
         table_to_foreign_keys[table]["incoming"].sort(
-            key=lambda fk: (fk["other_table"], fk["column"], fk["other_column"])
+            key=lambda fk: (
+                fk["other_table"] or "",
+                fk["column"] or "",
+                fk["other_column"] or "",
+            )
         )
         table_to_foreign_keys[table]["outgoing"].sort(
-            key=lambda fk: (fk["other_table"], fk["column"], fk["other_column"])
+            key=lambda fk: (
+                fk["other_table"] or "",
+                fk["column"] or "",
+                fk["other_column"] or "",
+            )
         )
 
     return table_to_foreign_keys
diff --git a/tests/test_utils.py b/tests/test_utils.py
index a535ca935c..d7680e24ee 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -921,3 +921,28 @@ def test_deep_dict_update(dict1, dict2, expected):
     assert result == expected
     # Check that the original dict1 was modified
     assert dict1 == expected
+
+
+def test_get_all_foreign_keys_mixed_implicit_and_explicit_targets():
+    # Two foreign keys from the same table to the same parent, one targeting
+    # the implicit primary key (other_column is None) and one an explicit
+    # column. Sorting the collected keys must not crash comparing None to str.
+    conn = sqlite3.connect(":memory:")
+    conn.executescript("""
+        CREATE TABLE parent (id INTEGER PRIMARY KEY, alt TEXT UNIQUE);
+        CREATE TABLE child (
+            p_id1 INTEGER,
+            p_id2 INTEGER,
+            FOREIGN KEY(p_id1) REFERENCES parent,
+            FOREIGN KEY(p_id2) REFERENCES parent(alt)
+        );
+        """)
+    result = utils.get_all_foreign_keys(conn)
+    assert result["parent"]["incoming"] == [
+        {"other_table": "child", "column": None, "other_column": "p_id1"},
+        {"other_table": "child", "column": "alt", "other_column": "p_id2"},
+    ]
+    assert result["child"]["outgoing"] == [
+        {"other_table": "parent", "column": "p_id1", "other_column": None},
+        {"other_table": "parent", "column": "p_id2", "other_column": "alt"},
+    ]