Do the de-duplication in _reproduce_stages

dvc/repo/reproduce.py

@@ -94,22 +94,12 @@ def reproduce(
             path, name=name, recursive=recursive, graph=active_graph
         )
 
-    ret = []
-    checked_stages = set()
-    for target in targets:
-        stages, these_checked_stages = _reproduce_stages(
-            active_graph, target, checked_stages, **kwargs
-        )
-        ret.extend(stages)
-        checked_stages.update(these_checked_stages)
-
-    return ret
+    return _reproduce_stages(active_graph, targets, **kwargs)
 
 
 def _reproduce_stages(
     G,
-    stage,
-    checked_stages,
+    stages,
     downstream=False,
     ignore_build_cache=False,
     single_item=False,
@@ -152,36 +142,45 @@ def _reproduce_stages(
     import networkx as nx
 
     if single_item:
-        pipeline = [stage]
-    elif downstream:
-        # NOTE (py3 only):
-        # Python's `deepcopy` defaults to pickle/unpickle the object.
-        # Stages are complex objects (with references to `repo`, `outs`,
-        # and `deps`) that cause struggles when you try to serialize them.
-        # We need to create a copy of the graph itself, and then reverse it,
-        # instead of using graph.reverse() directly because it calls
-        # `deepcopy` underneath -- unless copy=False is specified.
-        pipeline = nx.dfs_preorder_nodes(G.copy().reverse(copy=False), stage)
+        all_pipelines = stages
     else:
-        pipeline = nx.dfs_postorder_nodes(G, stage)
+        all_pipelines = []
+        for stage in stages:
+            if downstream:
+                # NOTE (py3 only):
+                # Python's `deepcopy` defaults to pickle/unpickle the object.
+                # Stages are complex objects (with references to `repo`,
+                # `outs`, and `deps`) that cause struggles when you try
+                # to serialize them. We need to create a copy of the graph
+                # itself, and then reverse it, instead of using
+                # graph.reverse() directly because it calls `deepcopy`
+                # underneath -- unless copy=False is specified.
+                all_pipelines += nx.dfs_preorder_nodes(
+                    G.copy().reverse(copy=False), stage
+                )
+            else:
+                all_pipelines += nx.dfs_postorder_nodes(G, stage)
+
+    pipeline = []
+    for stage in all_pipelines:
+        if stage not in pipeline:
+            pipeline.append(stage)
 
     result = []
-    these_checked_stages = []
-    for st in pipeline:
-        if st not in checked_stages:
-            try:
-                ret = _reproduce_stage(st, **kwargs)
-                these_checked_stages.append(st)
-
-                if len(ret) != 0 and ignore_build_cache:
-                    # NOTE: we are walking our pipeline from the top to the
-                    # bottom. If one stage is changed, it will be reproduced,
-                    # which tells us that we should force reproducing all of
-                    # the other stages down below, even if their direct
-                    # dependencies didn't change.
-                    kwargs["force"] = True
-
-                result.extend(ret)
-            except Exception as exc:
-                raise ReproductionError(st.relpath) from exc
-    return result, these_checked_stages
+    for stage in pipeline:
+        try:
+            ret = _reproduce_stage(stage, **kwargs)
+
+            if len(ret) != 0 and ignore_build_cache:
+                # NOTE: we are walking our pipeline from the top to the
+                # bottom. If one stage is changed, it will be reproduced,
+                # which tells us that we should force reproducing all of
+                # the other stages down below, even if their direct
+                # dependencies didn't change.
+                kwargs["force"] = True
+
+            result.extend(ret)
+        except Exception as exc:
+            raise ReproductionError(stage.relpath) from exc
+
+    return result