reports: RelatedPostings.all_meta_links() returns an iterator.

This preserves order.

conservancy_beancount/reports/accrual.py

@@ -553,7 +553,7 @@ class OutgoingReport(BaseReport):
         if raw_balance != posts.end_balance:
             balance_s = f'{raw_balance} ({balance_s})'
 
-        contract_links = posts.all_meta_links('contract')
+        contract_links = list(posts.all_meta_links('contract'))
         if contract_links:
             contract_s = ' , '.join(self.rt_wrapper.iter_urls(
                 contract_links, missing_fmt='<BROKEN RT LINK: {}>',

conservancy_beancount/reports/core.py

@@ -38,6 +38,7 @@ from pathlib import Path
 from beancount.core import amount as bc_amount
 
 from .. import data
+from .. import filters
 
 from typing import (
     cast,
@@ -293,14 +294,15 @@ class RelatedPostings(Sequence[data.Posting]):
     def __len__(self) -> int:
         return len(self._postings)
 
-    def all_meta_links(self, key: MetaKey) -> Set[str]:
-        retval: Set[str] = set()
+    def _all_meta_links(self, key: MetaKey) -> Iterator[str]:
         for post in self:
             try:
-                retval.update(post.meta.get_links(key))
+                yield from post.meta.get_links(key)
             except TypeError:
                 pass
-        return retval
+
+    def all_meta_links(self, key: MetaKey) -> Iterator[str]:
+        return filters.iter_unique(self._all_meta_links(key))
 
     def iter_with_balance(self) -> Iterator[Tuple[data.Posting, Balance]]:
         balance = MutableBalance()

tests/test_reports_related_postings.py

@@ -256,7 +256,7 @@ def test_all_meta_links_zero(count):
         post._replace(meta=data.Metadata(post.meta))
         for post in postings
     )
-    assert related.all_meta_links('approval') == set()
+    assert next(related.all_meta_links('approval'), None) is None
 
 def test_all_meta_links_singletons():
     postings = (
@@ -270,7 +270,7 @@ def test_all_meta_links_singletons():
         post._replace(meta=data.Metadata(post.meta))
         for post in postings
     )
-    assert related.all_meta_links('statement') == testutil.LINK_METADATA_STRINGS
+    assert set(related.all_meta_links('statement')) == testutil.LINK_METADATA_STRINGS
 
 def test_all_meta_links_multiples():
     postings = (
@@ -281,7 +281,18 @@ def test_all_meta_links_multiples():
         post._replace(meta=data.Metadata(post.meta))
         for post in postings
     )
-    assert related.all_meta_links('approval') == testutil.LINK_METADATA_STRINGS
+    assert set(related.all_meta_links('approval')) == testutil.LINK_METADATA_STRINGS
+
+def test_all_meta_links_preserves_order():
+    postings = (
+        testutil.Posting('Income:Donations', -10, approval=c)
+        for c in '121323'
+    )
+    related = core.RelatedPostings(
+        post._replace(meta=data.Metadata(post.meta))
+        for post in postings
+    )
+    assert list(related.all_meta_links('approval')) == list('123')
 
 def test_group_by_meta_zero():
     assert not list(core.RelatedPostings.group_by_meta([], 'metacurrency'))