From bc8ac26c8429dc976ddc1ee20cb5a503b598efef Mon Sep 17 00:00:00 2001
From: Paul Natsuo Kishimoto <mail@paul.kishimoto.name>
Date: Fri, 26 Jan 2024 12:04:41 +0100
Subject: [PATCH] Add .sdmx.quantity_to_message(), tests

---
 genno/compat/sdmx.py            | 19 +++++++++++--------
 genno/tests/compat/test_sdmx.py | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/genno/compat/sdmx.py b/genno/compat/sdmx.py
index b74dd5c3..7b663082 100644
--- a/genno/compat/sdmx.py
+++ b/genno/compat/sdmx.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Dict, Iterable, List, Mapping, Optional, Union
+from typing import Dict, Iterable, List, Mapping, Optional, Union
 
 from genno import Quantity
 
@@ -10,9 +10,6 @@
     HAS_SDMX = True
 
 
-if TYPE_CHECKING:
-    import sdmx.model.common
-
 __all__ = [
     "codelist_to_groups",
     "dataset_to_quantity",
@@ -94,10 +91,7 @@ def quantity_to_dataset(
 ) -> "sdmx.model.v21.Dataset":
     """Convert :class:`.Quantity to :class:`DataSet <sdmx.model.common.BaseDataSet>`.
 
-    Currently:
-
-    - `structure` must be provided.
-    - The resulting data set is structure-specific and flat (not grouped into Series).
+    The resulting data set is structure-specific and flat (not grouped into Series).
     """
     try:
         # URN of DSD stored on `qty` matches `structure`
@@ -124,3 +118,12 @@ def as_obs(key, value):
     ds.obs.extend(as_obs(key, value) for key, value in qty.to_series().items())
 
     return ds
+
+
+def quantity_to_message(
+    qty: Quantity, structure: "sdmx.model.v21.DataStructureDefinition", **kwargs
+) -> "sdmx.message.DataMessage":
+    """Convert :class:`.Quantity to :class:`DataMessage <sdmx.message.DataMessage>`."""
+    dm = sdmx.message.DataMessage(**kwargs)
+    dm.data.append(quantity_to_dataset(qty, structure))
+    return dm
diff --git a/genno/tests/compat/test_sdmx.py b/genno/tests/compat/test_sdmx.py
index 2b7383b0..f7f67d8f 100644
--- a/genno/tests/compat/test_sdmx.py
+++ b/genno/tests/compat/test_sdmx.py
@@ -7,6 +7,7 @@
     codelist_to_groups,
     dataset_to_quantity,
     quantity_to_dataset,
+    quantity_to_message,
 )
 from genno.testing import add_test_data
 
@@ -91,3 +92,17 @@ def test_quantity_to_dataset(dsd, dm):
 
     # Dataset is associated with its DSD
     assert dsd is ds.structured_by
+
+
+def test_quantity_to_message(dsd, dm):
+    ds = dm.data[0]
+    qty = dataset_to_quantity(ds)
+
+    header = dm.header
+
+    result = quantity_to_message(qty, structure=dsd, header=header)
+
+    # Currently False because `result.observation_dimension` is not set
+    with pytest.raises(AssertionError):
+        # Resulting message compares equal to the original ("round trip")
+        assert dm.compare(result)