[time] Support */N syntax in cron expressions (#15434)

esphome/components/time/__init__.py

@@ -123,8 +123,8 @@ def _parse_cron_part(part, min_value, max_value, special_mapping):
                 f"Can't have more than two '/' in one time expression, got {part}"
             )
         offset, repeat = data
-        offset_n = 0
+        offset_n = min_value
-        if offset:
+        if offset and offset not in ("*", "?"):
             offset_n = _parse_cron_int(
                 offset,
                 special_mapping,

tests/unit_tests/components/test_time.py

@@ -0,0 +1,80 @@
+"""Tests for time component cron expression parsing."""
+
+from esphome.components.time import _parse_cron_part
+
+
+def test_star_slash_seconds() -> None:
+    assert _parse_cron_part("*/10", 0, 60, {}) == {0, 10, 20, 30, 40, 50, 60}
+
+
+def test_star_slash_minutes() -> None:
+    assert _parse_cron_part("*/5", 0, 59, {}) == {
+        0,
+        5,
+        10,
+        15,
+        20,
+        25,
+        30,
+        35,
+        40,
+        45,
+        50,
+        55,
+    }
+
+
+def test_star_slash_hours() -> None:
+    assert _parse_cron_part("*/2", 0, 23, {}) == {
+        0,
+        2,
+        4,
+        6,
+        8,
+        10,
+        12,
+        14,
+        16,
+        18,
+        20,
+        22,
+    }
+
+
+def test_star_slash_days_of_month() -> None:
+    """days_of_month starts at 1, not 0."""
+    assert _parse_cron_part("*/5", 1, 31, {}) == {1, 6, 11, 16, 21, 26, 31}
+
+
+def test_question_slash() -> None:
+    assert _parse_cron_part("?/10", 0, 60, {}) == {0, 10, 20, 30, 40, 50, 60}
+
+
+def test_empty_offset_slash() -> None:
+    """Empty offset defaults to min_value."""
+    assert _parse_cron_part("/10", 0, 60, {}) == {0, 10, 20, 30, 40, 50, 60}
+
+
+def test_empty_offset_slash_nonzero_min() -> None:
+    """Empty offset defaults to min_value, not 0."""
+    assert _parse_cron_part("/5", 1, 31, {}) == {1, 6, 11, 16, 21, 26, 31}
+
+
+def test_numeric_offset_slash() -> None:
+    assert _parse_cron_part("5/10", 0, 60, {}) == {5, 15, 25, 35, 45, 55}
+
+
+def test_star() -> None:
+    assert _parse_cron_part("*", 0, 59, {}) == set(range(0, 60))
+
+
+def test_question() -> None:
+    assert _parse_cron_part("?", 0, 59, {}) == set(range(0, 60))
+
+
+def test_range() -> None:
+    assert _parse_cron_part("1-5", 0, 59, {}) == {1, 2, 3, 4, 5}
+
+
+def test_single_value() -> None:
+    assert _parse_cron_part("30", 0, 59, {}) == {30}