fix: use left join when adding tables instead of inner join

Author: ManonMarchand

CHANGES.rst

@@ -13,6 +13,13 @@ ipac.nexsci.nasa_exoplanet_archive
 
 - Fixed InvalidTableError for DI_STARS_EXEP and TD tables. [#3189]
 
+simbad
+^^^^^^
+
+- fix: when adding a measurement table in the votable_fields, if a measurement table is
+  empty for an object, there will now be a line with masked values instead of no line in
+  the result [#3199]
+
 xmatch
 ^^^^^^
 

astroquery/simbad/core.py

@@ -347,7 +347,7 @@ def _add_table_to_output(self, table):
         self.columns_in_output += [_Column(table, column, alias)
                                    for column, alias in zip(columns, alias)]
         self.joins += [_Join(table, _Column("basic", link["target_column"]),
-                             _Column(table, link["from_column"]))]
+                             _Column(table, link["from_column"]), "LEFT JOIN")]
 
     def add_votable_fields(self, *args):
         """Add columns to the output of a SIMBAD query.

astroquery/simbad/tests/test_simbad.py

@@ -214,7 +214,7 @@ def test_add_table_to_output(monkeypatch):
     simbad_instance._add_table_to_output("mesDiameter")
     assert simbad.core._Join("mesdiameter",
                              simbad.core._Column("basic", "oid"),
-                             simbad.core._Column("mesdiameter", "oidref")
+                             simbad.core._Column("mesdiameter", "oidref"), "LEFT JOIN"
                              ) in simbad_instance.joins
     assert simbad.core._Column("mesdiameter", "bibcode", "mesdiameter.bibcode"
                                ) in simbad_instance.columns_in_output

astroquery/simbad/tests/test_simbad_remote.py

@@ -119,6 +119,16 @@ def test_query_object(self):
         result = self.simbad.query_object("NGC [0-9]*", wildcard=True)
         assert all(matched_id.startswith("NGC") for matched_id in result["matched_id"].data.data)
 
+    def test_query_object_with_measurement_table(self):
+        # regression for #3197
+        self.simbad.reset_votable_fields()
+        self.simbad.add_votable_fields("mesdistance")
+        vega = self.simbad.query_object("vega")
+        # there is one response line
+        assert len(vega) == 1
+        # even if the measurement table is empty
+        assert bool(vega["mesdistance.dist"][0].mask)
+
     def test_query_criteria(self):
         simbad_instance = Simbad()
         simbad_instance.add_votable_fields("otype")
@@ -199,7 +209,8 @@ def test_add_votable_fields(self):
         # tables also require a join
         assert _Join("otypes",
                      _Column("basic", "oid"),
-                     _Column("otypes", "oidref")) == simbad_instance.joins[0]
+                     _Column("otypes", "oidref"),
+                     "LEFT JOIN") == simbad_instance.joins[0]
         # tables that have been renamed should warn
         with pytest.warns(DeprecationWarning, match="'iue' has been renamed 'mesiue'.*"):
             simbad_instance.add_votable_fields("IUE")