Backing out of requesting alt_identifiers every time.

This is supposed to address bug #522.  The code as it was up to here
would have needed aggregation of alt_identifiers (which are n:1 over
resources), or else we see duplicate capabilities.

But at least some registry operators prefer to not hit the rr.alt_identifier
table by default as long as it's not clear who will actually look at these
alternate identifiers.

But we maintain the alt identifiers in describe(); to do that, there's now
get_alternate_identifiers method returning these.

The downside: describe() now does an uncached network query.  Perhaps
we want to at least hide failures from there?  On the other hand, once
we are here we can also call get_contact() here; should we?

pyvo/registry/regtap.py

@@ -498,8 +498,7 @@ class RegistryResource(dalq.Record):
         (f"\n  ivo_string_agg(COALESCE(intf_role, ''), '{TOKEN_SEP}')",
             "intf_roles"),
         (f"\n  ivo_string_agg(COALESCE(cap_description, ''), '{TOKEN_SEP}')",
-            "cap_descriptions"),
-        "alt_identifier"]
+            "cap_descriptions")]
 
     def __init__(self, results, index, *, session=None):
         dalq.Record.__init__(self, results, index, session=session)
@@ -599,14 +598,6 @@ def reference_url(self):
         """
         return self.get("reference_url", decode=True)
 
-    @property
-    def alt_identifier(self):
-        """Alternative identifier.
-
-        It is often used to provide the resource associated DOI.
-        """
-        return self.get("alt_identifier", decode=True)
-
     @property
     def creators(self):
         """
@@ -1013,8 +1004,14 @@ def describe(self, *, verbose=False, width=78, file=None):
                 else:
                     print(f"Authors: {', '.join(creators[:nmax_authors])} et al.\n"
                     "See creators attribute for the complete list of authors.", file=file)
-            if self.alt_identifier:
-                print(f"Alternative identifier: {self.alt_identifier}", file=file)
+
+            alt_identifiers = self.get_alt_identifiers()
+            if alt_identifiers:
+                print(
+                    "Alternative identifier(s): {}".format(
+                        ", ".join(alt_identifiers)),
+                    file=file)
+
             if self.reference_url:
                 print("More info: " + self.reference_url, file=file)
 
@@ -1043,6 +1040,18 @@ def get_contact(self):
 
         return "\n".join(contacts)
 
+    def get_alt_identifiers(self):
+        """return a sequence of non-ivoid identifiers for the resource.
+
+        This is typically used to provide a DOI for the resource.
+        """
+        res = get_RegTAP_service().run_sync("""
+            SELECT alt_identifier
+            FROM rr.alt_identifier
+            WHERE ivoid={}""".format(
+                rtcons.make_sql_literal(self.ivoid)))
+        return [r["alt_identifier"] for r in res]
+
     def _build_vosi_column(self, column_row):
         """
         return a io.vosi.vodataservice.Column element for a

pyvo/registry/tests/test_regtap.py

@@ -720,6 +720,15 @@ def test_get_contact():
             " <gavo@ari.uni-heidelberg.de>")
 
 
+@pytest.mark.remote_data
+def test_get_alt_identifier():
+    rsc = _makeRegistryRecord(ivoid="ivo://cds.vizier/i/337")
+    assert set(rsc.get_alt_identifiers()) == {
+        'doi:10.26093/cds/vizier.1337',
+        'bibcode:doi:10.5270/esa-ogmeula',
+        'bibcode:2016yCat.1337....0G'}
+
+
 @pytest.mark.remote_data
 class TestDatamodelQueries:
     # right now, the data model queries are all rather sui generis, and
@@ -754,6 +763,7 @@ def test_unique_standard_id(self):
             intf_roles=["std"])
         assert rsc.standard_id == "ivo://ivoa.net/std/tap"
 
+    @pytest.mark.remote_data
     def test_describe_multi(self, flash_service):
         out = io.StringIO()
         flash_service.describe(verbose=True, file=out)
@@ -765,9 +775,10 @@ def test_describe_multi(self, flash_service):
         assert "Multi-capability service" in output
         assert "Source: 1996A&A...312..539S" in output
         assert "Authors: Wolf" in output
-        assert "Alternative identifier: doi:10.21938/" in output
+        assert "Alternative identifier(s): doi:10.21938/" in output
         assert "More info: http://dc.zah" in output
 
+    @pytest.mark.remote_data
     def test_describe_long_authors_list(self):
         """Check that long list of authors use et al.."""
         rsc = _makeRegistryRecord(
@@ -785,6 +796,7 @@ def test_describe_long_authors_list(self):
         # output should cut at 5 authors
         assert "Authors: a, a, a, a, a et al." in output
 
+    @pytest.mark.remote_data
     def test_describe_long_author_name(self):
         """Check that long author names are truncated."""
         rsc = _makeRegistryRecord(

pyvo/registry/tests/test_rtcons.py

@@ -458,8 +458,7 @@ def test_expected_columns(self):
             "\n  ivo_string_agg(COALESCE(standard_id, ''), ':::py VO sep:::') AS standard_ids, "
             "\n  ivo_string_agg(COALESCE(intf_type, ''), ':::py VO sep:::') AS intf_types, "
             "\n  ivo_string_agg(COALESCE(intf_role, ''), ':::py VO sep:::') AS intf_roles, "
-            "\n  ivo_string_agg(COALESCE(cap_description, ''), ':::py VO sep:::') AS cap_descriptions, "
-            "alt_identifier")
+            "\n  ivo_string_agg(COALESCE(cap_description, ''), ':::py VO sep:::') AS cap_descriptions")
 
     def test_group_by_columns(self):
         # Again, this will break as regtap.RegistryResource.expected_columns
@@ -480,8 +479,7 @@ def test_group_by_columns(self):
                     "source_format, "
                     "source_value, "
                     "region_of_regard, "
-                    "waveband, "
-                    "alt_identifier"))
+                    "waveband"))
 
     def test_joined_tables(self):
         expected_tables = [
@@ -491,7 +489,6 @@ def test_joined_tables(self):
             "rr.resource",
             "rr.capability",
             "rr.interface",
-            "rr.alt_identifier"
         ]
         assert all(table in _build_regtap_query_with_fake([rtcons.Author("%Hubble%")])
                    for table in expected_tables)
@@ -519,4 +516,4 @@ def test_all_constraints():
         'reference_url', 'creator_seq', 'created', 'updated',
         'rights', 'content_type', 'source_format', 'source_value',
         'region_of_regard', 'waveband', 'access_urls', 'standard_ids',
-        'intf_types', 'intf_roles', 'cap_descriptions', 'alt_identifier')
+        'intf_types', 'intf_roles', 'cap_descriptions')