Allow table.get() to look up rows by column values

table.get() now accepts column=value keyword arguments and returns the
first matching row, so a row can be fetched by a unique column rather
than only by its primary key. Passing both a primary key and keyword
arguments raises ValueError, and calling get() with neither raises
TypeError.

Refs #588

tests/test_get.py

@@ -30,3 +30,71 @@ def test_get_not_found(argument, expected_msg, fresh_db):
         fresh_db.table("dogs").get(argument)
     if expected_msg is not None:
         assert expected_msg == excinfo.value.args[0]
+
+
+def test_get_by_column(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert_all(
+        [
+            {"id": 1, "name": "Cleo", "age": 4},
+            {"id": 2, "name": "Pancakes", "age": 2},
+        ],
+        pk="id",
+    )
+    assert dogs.get(name="Pancakes") == {"id": 2, "name": "Pancakes", "age": 2}
+
+
+def test_get_by_multiple_columns(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert_all(
+        [
+            {"id": 1, "name": "Cleo", "age": 4},
+            {"id": 2, "name": "Cleo", "age": 2},
+        ],
+        pk="id",
+    )
+    assert dogs.get(name="Cleo", age=2)["id"] == 2
+
+
+def test_get_by_column_sets_last_pk(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert({"id": 5, "name": "Cleo", "age": 4}, pk="id")
+    dogs.get(name="Cleo")
+    assert dogs.last_pk == 5
+
+
+def test_get_by_column_compound_pk_sets_last_pk(fresh_db):
+    table = fresh_db.table("records")
+    table.insert_all(
+        [{"a": 1, "b": 2, "note": "x"}, {"a": 1, "b": 3, "note": "y"}],
+        pk=("a", "b"),
+    )
+    assert table.get(note="y")["b"] == 3
+    assert table.last_pk == (1, 3)
+
+
+def test_get_by_column_on_rowid_table(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert({"name": "Cleo", "age": 4})
+    assert dogs.get(name="Cleo")["name"] == "Cleo"
+
+
+def test_get_by_column_not_found(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert({"id": 1, "name": "Cleo", "age": 4}, pk="id")
+    with pytest.raises(NotFoundError):
+        dogs.get(name="Pancakes")
+
+
+def test_get_rejects_pk_and_column(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert({"id": 1, "name": "Cleo", "age": 4}, pk="id")
+    with pytest.raises(ValueError):
+        dogs.get(1, name="Cleo")
+
+
+def test_get_requires_argument(fresh_db):
+    dogs = fresh_db.table("dogs")
+    dogs.insert({"id": 1, "name": "Cleo", "age": 4}, pk="id")
+    with pytest.raises(TypeError):
+        dogs.get()