Merge pull request #2248 from Zac-HD/unique-sampled-bugfix

Fix UniqueSampledListStrategy bug
HypothesisWorks · Dec 1, 2019 · 8892559 · 8892559
2 parents 894c252 + 5fcda2c
commit 8892559
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diff --git a/hypothesis-python/RELEASE.rst b/hypothesis-python/RELEASE.rst
@@ -0,0 +1,5 @@
+RELEASE_TYPE: patch
+
+This patch fixes a rare internal error in strategies for a list of
+unique items sampled from a short non-unique sequence (:issue:`2247`).
+The bug was discovered via :pypi:`hypothesis-jsonschema`.
diff --git a/hypothesis-python/src/hypothesis/searchstrategy/collections.py b/hypothesis-python/src/hypothesis/searchstrategy/collections.py
@@ -188,7 +188,7 @@ def do_draw(self, data):
 
         remaining = LazySequenceCopy(self.element_strategy.elements)
 
-        while should_draw.more():
+        while remaining and should_draw.more():
             i = len(remaining) - 1
             j = cu.integer_range(data, 0, i)
             if j != i:

diff --git a/hypothesis-python/tests/cover/test_sampled_from.py b/hypothesis-python/tests/cover/test_sampled_from.py
@@ -92,3 +92,8 @@ def test_does_not_include_duplicates_even_when_duplicated_in_collection(ls):
 @given(st.lists(st.sampled_from(hrange(100)), max_size=3, unique=True))
 def test_max_size_is_respected_with_unique_sampled_from(ls):
     assert len(ls) <= 3
+
+
+@given(st.lists(st.sampled_from([0, 0.0]), unique=True, min_size=1))
+def test_issue_2247_regression(ls):
+    assert len(ls) == 1