test: Verify pylist sources drop unneeded columns (#650)

python/pytests/golden/pylist_source_test/test_read_pylist_ignore_column.jsonl

@@ -0,0 +1 @@
+{"_time":"1996-12-19T16:39:57.000","_subsort":0,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:39:57","user":"A","n":10}

python/pytests/golden/pylist_source_test/test_read_pylist_ignore_column_1.jsonl

@@ -0,0 +1,3 @@
+{"_time":"1996-12-19T16:39:57.000","_subsort":0,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:39:57","user":"A","n":10.0}
+{"_time":"1996-12-19T16:40:57.000","_subsort":1,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:40:57","user":"A","n":10.0}
+{"_time":"1996-12-19T16:41:57.000","_subsort":2,"_key_hash":12960666915911099378,"_key":"A","time":"1996-12-19T16:41:57","user":"A","n":null}

python/pytests/pylist_source_test.py

@@ -36,3 +36,20 @@ def test_read_pylist_lists(golden) -> None:
         ]
     )
     golden.jsonl(source)
+
+def test_read_pylist_ignore_column(golden) -> None:
+    # Schema is determined from first row, and doesn't contain an "m" column.
+    source = kd.sources.PyList(
+        [{"time": "1996-12-19T16:39:57", "user": "A", "n": 10}],
+        time_column_name="time",
+        key_column_name="user",
+    )
+    golden.jsonl(source)
+
+    source.add_rows(
+        [
+            {"time": "1996-12-19T16:40:57", "user": "A", "m": 83, "n": 10},
+            {"time": "1996-12-19T16:41:57", "user": "A", "m": 12},
+        ]
+    )
+    golden.jsonl(source)