YMAKE-144: Fix RuntimeError: dictionary changed size during iteration

ref:919db9913468e91d031bbd511beeacdcfdd74489

2 files changed, 30 insertions, 2 deletions

diff --git a/library/python/runtime_py3/importer.pxi b/library/python/runtime_py3/importer.pxi
index 904f94dea2..579a276d02 100644
--- a/library/python/runtime_py3/importer.pxi
+++ b/library/python/runtime_py3/importer.pxi
@@ -451,11 +451,15 @@ class ArcadiaSourceFinder:
             # Yield from cache
             import re
             rx = re.compile(re.escape(package_prefix) + r'([^.]+)$')
+            # Save result to temporary list to prevent 'RuntimeError: dictionary changed size during iteration'
+            found = []
             for mod, path in self.module_path_cache.items():
                 if path is not None:
                     m = rx.match(mod)
                     if m:
-                        yield prefix + m.group(1), self.is_package(mod)
+                        found.append((prefix + m.group(1), self.is_package(mod)))
+            for cm in found:
+                yield cm
 
             # Yield from file system
             for path in paths:
@@ -491,7 +495,7 @@ class ArcadiaSourceFinder:
                 return package_paths
 
     def _cache_module_path(self, fullname, find_package_only=False):
-        """ 
+        """
             Find module path or package directory paths and save result in the cache
 
             find_package_only=True - don't try to find module
diff --git a/library/python/runtime_py3/test/test_arcadia_source_finder.py b/library/python/runtime_py3/test/test_arcadia_source_finder.py
index ff80d0a0a2..c01435f7df 100644
--- a/library/python/runtime_py3/test/test_arcadia_source_finder.py
+++ b/library/python/runtime_py3/test/test_arcadia_source_finder.py
@@ -315,3 +315,27 @@ class TestEmptyResources(ArcadiaSourceFinderTestCase):
 
     def test_iter_modules(self):
         assert [] == list(self.arcadia_source_finder.iter_modules('', 'PFX.'))
+
+
+class TestDictionaryChangedSizeDuringIteration(ArcadiaSourceFinderTestCase):
+    def _get_mock_fs(self):
+        return '''
+           home:
+             arcadia:
+               project:
+                 lib1:
+                   mod1.py: ''
+                 lib2:
+                   mod2.py: ''
+        '''
+
+    def _get_mock_resources(self):
+        return {
+            b'py/namespace/unique_prefix1/project/lib1': b'project.lib1.',
+            b'py/namespace/unique_prefix1/project/lib2': b'project.lib2.',
+        }
+
+    def test_no_crash_on_recusive_iter_modules(self):
+        for package in self.arcadia_source_finder.iter_modules('project.', ''):
+            for _ in self.arcadia_source_finder.iter_modules(package[0], ''):
+                pass