Make transitive_deps as a topologically sorted list

templates/gRPC-C++.podspec.template

@@ -35,7 +35,7 @@
     return "abseil/" + label[5:].replace(":", "/")
 
   def lib_and_transitive_deps(lib):
-    return list(sorted(set({lib} | lib_maps[lib].transitive_deps)))
+    return list(sorted(set({lib} | set(lib_maps[lib].transitive_deps))))
 
   def non_abseil_lib_and_transitive_deps(lib):
     return [l for l in lib_and_transitive_deps(lib) if not is_absl_lib(l)]

templates/gRPC-Core.podspec.template

@@ -34,7 +34,7 @@
     return "abseil/" + label[5:].replace(":", "/")
 
   def lib_and_transitive_deps(lib):
-    return list(sorted(set({lib} | lib_maps[lib].transitive_deps)))
+    return list(sorted(set({lib} | set(lib_maps[lib].transitive_deps))))
 
   def non_abseil_lib_and_transitive_deps(lib):
     return [l for l in lib_and_transitive_deps(lib) if not is_absl_lib(l)]

tools/buildgen/plugins/transitive_dependencies.py

@@ -16,27 +16,32 @@
 This takes the list of libs, node_modules, and targets from our
 yaml dictionary, and adds to each the transitive closure
 of the list of dependencies.
-
 """
 
 
-def get_lib(libs, name):
-    try:
-        return next(lib for lib in libs if lib['name'] == name)
-    except StopIteration:
-        return None
+def transitive_deps(lib_map, node):
+    """Returns a list of transitive dependencies from node.
+
+    Recursively iterate all dependent node in a depth-first fashion and
+    list a result using a topological sorting.
+    """
+    result = []
+    seen = set()
+    start = node
 
+    def recursive_helper(node):
+        if node is None:
+            return
+        for dep in node.get("deps", []):
+            if dep not in seen:
+                seen.add(dep)
+                next_node = lib_map.get(dep)
+                recursive_helper(next_node)
+        if node is not start:
+            result.insert(0, node["name"])
 
-def transitive_deps(lib, libs):
-    if lib is not None and 'deps' in lib:
-        # Recursively call transitive_deps on each dependency, and take the union
-        return set.union(
-            set(lib['deps']), *[
-                set(transitive_deps(get_lib(libs, dep), libs))
-                for dep in lib['deps']
-            ])
-    else:
-        return set()
+    recursive_helper(node)
+    return result
 
 
 def mako_plugin(dictionary):
@@ -44,15 +49,15 @@ def mako_plugin(dictionary):
 
     Iterate over each list and check each item for a deps list. We add a
     transitive_deps property to each with the transitive closure of those
-  dependency lists.
+    dependency lists. The result list is sorted in a topological ordering.
     """
-    libs = dictionary.get('libs')
+    lib_map = {lib['name']: lib for lib in dictionary.get('libs')}
 
     for target_name, target_list in dictionary.items():
         for target in target_list:
             if isinstance(target, dict) and 'deps' in target:
-                target['transitive_deps'] = transitive_deps(target, libs)
+                target['transitive_deps'] = transitive_deps(lib_map, target)
 
     python_dependencies = dictionary.get('python_dependencies')
-    python_dependencies['transitive_deps'] = (transitive_deps(
-        python_dependencies, libs))
+    python_dependencies['transitive_deps'] = transitive_deps(
+        lib_map, python_dependencies)