reports: Add RelatedPostings.all_meta_links() method.

conservancy_beancount/reports/core.py

@@ -140,6 +140,15 @@ class RelatedPostings(Sequence[data.Posting]):
     def add(self, post: data.Posting) -> None:
         self._postings.append(post)
 
+    def all_meta_links(self, key: MetaKey) -> Set[str]:
+        retval: Set[str] = set()
+        for post in self:
+            try:
+                retval.update(post.meta.get_links(key))
+            except TypeError:
+                pass
+        return retval
+
     def clear(self) -> None:
         self._postings.clear()
 

tests/test_reports_related_postings.py

@@ -196,6 +196,43 @@ def test_meta_values_many_types():
         related.add(testutil.Posting('Income:Donations', -index, key=value))
     assert related.meta_values('key') == expected
 
+@pytest.mark.parametrize('count', range(3))
+def test_all_meta_links_zero(count):
+    postings = (
+        testutil.Posting('Income:Donations', -n, testkey=str(n))
+        for n in range(count)
+    )
+    related = core.RelatedPostings(
+        post._replace(meta=data.Metadata(post.meta))
+        for post in postings
+    )
+    assert related.all_meta_links('approval') == set()
+
+def test_all_meta_links_singletons():
+    postings = (
+        testutil.Posting('Income:Donations', -10, statement=value)
+        for value in itertools.chain(
+            testutil.NON_LINK_METADATA_STRINGS,
+            testutil.LINK_METADATA_STRINGS,
+            testutil.NON_STRING_METADATA_VALUES,
+        ))
+    related = core.RelatedPostings(
+        post._replace(meta=data.Metadata(post.meta))
+        for post in postings
+    )
+    assert related.all_meta_links('statement') == testutil.LINK_METADATA_STRINGS
+
+def test_all_meta_links_multiples():
+    postings = (
+        testutil.Posting('Income:Donations', -10, approval=' '.join(value))
+        for value in itertools.permutations(testutil.LINK_METADATA_STRINGS, 2)
+    )
+    related = core.RelatedPostings(
+        post._replace(meta=data.Metadata(post.meta))
+        for post in postings
+    )
+    assert related.all_meta_links('approval') == testutil.LINK_METADATA_STRINGS
+
 def test_group_by_meta_zero():
     assert len(core.RelatedPostings.group_by_meta([], 'metacurrency')) == 0