fix(plan): show each item of a changed list property

snowcap/blueprint.py

@@ -4,6 +4,7 @@
 from collections import defaultdict
 from concurrent.futures import ThreadPoolExecutor, as_completed
 from dataclasses import dataclass
+from itertools import zip_longest
 from typing import (
     Any,
     Generator,
@@ -887,6 +888,29 @@ def _summarize_plan_value(value, max_len: int = 60) -> str:
     return f"<{lines} {unit}, {len(text)} chars>"
 
 
+def _plan_value_rows(key: str, before, after) -> list[list[str]]:
+    """Rows of the plan table for one changed property.
+
+    A list is shown one item per row, before and after side by side, so the plan names the
+    items that changed. As one value, a list of IP addresses or triggers soon outgrows the
+    table width and collapses to its length. A dict item is shown as `key: value` pairs, and
+    an item is shown in full however long it is: only a multiline item collapses, because the
+    table cannot lay out a newline.
+    """
+    if isinstance(before, list) or isinstance(after, list):
+        pairs = list(zip_longest(map(_plan_item, before or []), map(_plan_item, after or []), fillvalue=""))
+        if pairs:
+            return [[key if index == 0 else "", old, new] for index, (old, new) in enumerate(pairs)]
+    return [[key, _summarize_plan_value(before), _summarize_plan_value(after)]]
+
+
+def _plan_item(item) -> str:
+    if isinstance(item, dict):
+        item = ", ".join(f"{field}: {value}" for field, value in item.items())
+    text = str(item)
+    return _summarize_plan_value(text) if "\n" in text else text
+
+
 def _render_table(rows: list[list[str]], headers: list[str]) -> str:
     """
     Render a table with box-drawing characters.
@@ -1191,14 +1215,7 @@ def _dump_plan_text(plan: Plan) -> str:
                 for key, new_value in change.delta.items():
                     if key.startswith("_"):
                         continue
-                    before = change.before.get(key, "")
-                    rows.append(
-                        [
-                            key,
-                            _summarize_plan_value(before),
-                            _summarize_plan_value(new_value),
-                        ]
-                    )
+                    rows.extend(_plan_value_rows(key, change.before.get(key, ""), new_value))
 
                 if rows:
                     table = _render_table(rows, ["Property", "Before", "After"])

tests/test_blueprint.py

@@ -2849,6 +2849,54 @@ def test_tables_are_listed_from_account_usage_when_it_is_on(self):
         assert not any("SHOW TABLES IN ACCOUNT" in statement for statement in sql)
 
 
+@pytest.mark.parametrize(
+    "resource_cls, urn, key, before, after, expected_rows",
+    [
+        (
+            res.NetworkPolicy,
+            "urn::ABCD123:network_policy/OFFICE",
+            "allowed_ip_list",
+            ["10.0.0.1/32", "10.0.0.2/32", "10.0.0.3/32", "10.0.0.4/32", "10.0.0.5/32"],
+            ["10.0.0.1/32", "10.0.0.2/32", "10.0.0.3/32", "10.0.0.4/32", "10.0.0.6/32"],
+            [
+                "│ allowed_ip_list │ 10.0.0.1/32 │ 10.0.0.1/32 │",
+                "│                 │ 10.0.0.2/32 │ 10.0.0.2/32 │",
+                "│                 │ 10.0.0.3/32 │ 10.0.0.3/32 │",
+                "│                 │ 10.0.0.4/32 │ 10.0.0.4/32 │",
+                "│                 │ 10.0.0.5/32 │ 10.0.0.6/32 │",
+            ],
+        ),
+        (
+            res.HybridTable,
+            "urn::ABCD123:hybrid_table/DB.SCH.LISTINGS",
+            "indexes",
+            [{"name": "IDX_CITY", "columns": ["CITY"]}],
+            [
+                {"name": "IDX_CITY", "columns": ["CITY"]},
+                {"name": "IDX_REGION", "columns": ["STATE", "COUNTY", "CITY", "POSTAL_CODE"]},
+            ],
+            [
+                "│ indexes  │ name: IDX_CITY, columns: ['CITY'] │ name: IDX_CITY, columns: ['CITY']                                     │",
+                "│          │                                   │ name: IDX_REGION, columns: ['STATE', 'COUNTY', 'CITY', 'POSTAL_CODE'] │",
+            ],
+        ),
+    ],
+)
+def test_plan_text_shows_each_item_of_a_changed_list(resource_cls, urn, key, before, after, expected_rows):
+    """A list longer than the table's value width is shown one item per row, so the plan says
+    which items changed instead of only how long the list is."""
+    change = UpdateResource(
+        urn=parse_URN(urn),
+        resource_cls=resource_cls,
+        before={key: before},
+        after={key: after},
+        delta={key: after},
+    )
+    plan_lines = [line.strip() for line in strip_ansi(dump_plan([change], format="text")).splitlines()]
+    start = plan_lines.index(expected_rows[0])
+    assert plan_lines[start : start + len(expected_rows)] == expected_rows
+
+
 class TestSummarizePlanValue:
     """The plan table must not dump a multiline SQL body (alert THEN, task body)."""