Allow for specificaion of "specific" sample windows

In most cases people will want to set "relative" sample windows, i.e.
"3 days" to sample the last three days. However, there are some cases
where people will want to "specific" sample windows for some chunk of
historic time, i.e. `{'start': '2024-01-01', 'end': '2024-01-31'}`.

core/dbt/cli/option_types.py

@@ -1,5 +1,6 @@
 from typing import Optional
 
+import pytz
 from click import Choice, Context, Parameter, ParamType
 
 from dbt.config.utils import normalize_warn_error_options, parse_cli_yaml_string
@@ -104,7 +105,16 @@ def convert(
 
         if isinstance(value, str):
             try:
-                return SampleWindow.from_relative_string(value)
+                # Try and identify if it's a "dict" or a "str"
+                if value.lstrip()[0] == "{":
+                    param_option_name: str = param.opts[0] if param.opts else param.name  # type: ignore
+                    parsed_dict = parse_cli_yaml_string(value, param_option_name.strip("-"))
+                    sample_window = SampleWindow.from_dict(parsed_dict)
+                    sample_window.start = sample_window.start.replace(tzinfo=pytz.UTC)
+                    sample_window.end = sample_window.end.replace(tzinfo=pytz.UTC)
+                    return sample_window
+                else:
+                    return SampleWindow.from_relative_string(value)
             except Exception as e:
                 self.fail(e.__str__(), param, ctx)
         else:

tests/unit/cli/test_option_types.py

@@ -1,7 +1,13 @@
+from datetime import datetime
+from typing import Union
+
+import freezegun
 import pytest
+import pytz
 from click import BadParameter, Option
 
-from dbt.cli.option_types import YAML
+from dbt.cli.option_types import YAML, SampleWindowType
+from dbt.event_time.sample_window import SampleWindow
 
 
 class TestYAML:
@@ -24,3 +30,51 @@ def test_yaml_init_invalid_yaml_str(self, invalid_yaml_str):
         with pytest.raises(BadParameter) as e:
             YAML().convert(invalid_yaml_str, Option(["--vars"]), None)
         assert "--vars" in e.value.format_message()
+
+
+class TestSampleWindowType:
+    @pytest.mark.parametrize(
+        "input,expected_result",
+        [
+            (
+                "{'start': '2025-01-24', 'end': '2025-01-27'}",
+                SampleWindow(
+                    start=datetime(2025, 1, 24, 0, 0, 0, 0, pytz.UTC),
+                    end=datetime(2025, 1, 27, 0, 0, 0, 0, pytz.UTC),
+                ),
+            ),
+            (
+                "{'tart': '2025-01-24', 'bend': '2025-01-27'}",
+                BadParameter('Field "start" of type datetime is missing in SampleWindow instance'),
+            ),
+            (
+                "{}",
+                BadParameter('Field "start" of type datetime is missing in SampleWindow instance'),
+            ),
+            (
+                "cats",
+                BadParameter(
+                    "Runtime Error\n  Cannot load SAMPLE_WINDOW from 'cats'. Must be of form 'DAYS_INT GRAIN_SIZE'."
+                ),
+            ),
+        ],
+    )
+    def test_convert(self, input: str, expected_result: Union[SampleWindow, Exception]):
+        try:
+            result = SampleWindowType().convert(input, Option(["--sample-window"]), None)
+            assert result == expected_result
+        except Exception as e:
+            assert str(e) == str(expected_result)
+
+    # this had to be a seprate test case because the @freezegun.freeze_time
+    # was screwing up the instantiation of SampleWindow.from_dict calls for the
+    # other test cases
+    @freezegun.freeze_time("2025-01-28T02:03:0Z")
+    def test_convert_relative(self):
+        input = "3 days"
+        expected_result = SampleWindow(
+            start=datetime(2025, 1, 25, 2, 3, 0, 0, pytz.UTC),
+            end=datetime(2025, 1, 28, 2, 3, 0, 0, pytz.UTC),
+        )
+        result = SampleWindowType().convert(input, Option(["--sample-window"]), None)
+        assert result == expected_result