fix(solver): skip seen "graph" nodes

sharply decreases slowness :)

poetry/puzzle/solver.py

@@ -221,7 +221,9 @@ class Solver:
         except SolveFailure as e:
             raise SolverProblemError(e)
 
-        graph = self._build_graph(self._package, packages)
+        # TODO why is there a lingering variable state / stack during install when invoked via `poetry update`?
+        # NOTE passing explicit empty array for seen to reset between invocations during update + install cycle
+        graph = self._build_graph(self._package, packages, seen=[])
 
         depths = []
         final_packages = []
@@ -237,7 +239,7 @@ class Solver:
         return final_packages, depths
 
     def _build_graph(
-        self, package, packages, previous=None, previous_dep=None, dep=None
+        self, package, packages, previous=None, previous_dep=None, dep=None, seen=[]
     ):  # type: (...) -> Dict[str, Any]
         if not previous:
             category = "dev"
@@ -254,6 +256,12 @@ class Solver:
             "children": childrens,
         }
 
+        # skip already traversed packages
+        if package in seen:
+            return graph
+        else:
+            seen.append(package)
+
         if previous_dep and previous_dep is not dep and previous_dep.name == dep.name:
             return graph
 
@@ -302,7 +310,7 @@ class Solver:
                             continue
 
                     child_graph = self._build_graph(
-                        pkg, packages, graph, dependency, dep or dependency
+                        pkg, packages, graph, dependency, dep or dependency, seen=seen
                     )
 
                     if not is_activated:

tests/puzzle/test_solver.py

@@ -619,17 +619,17 @@ def test_solver_with_dependency_in_both_main_and_dev_dependencies(
     check_solver_result(
         ops,
         [
-            {"job": "install", "package": package_d},
             {"job": "install", "package": package_b},
-            {"job": "install", "package": package_c},
             {"job": "install", "package": package_a},
+            {"job": "install", "package": package_c},
+            {"job": "install", "package": package_d},
         ],
     )
 
-    b = ops[1].package
+    b = ops[0].package
+    a = ops[1].package
     c = ops[2].package
-    d = ops[0].package
-    a = ops[3].package
+    d = ops[3].package
 
     assert d.category == "dev"
     assert c.category == "dev"
@@ -670,18 +670,18 @@ def test_solver_with_dependency_in_both_main_and_dev_dependencies_with_one_more_
     check_solver_result(
         ops,
         [
-            {"job": "install", "package": package_b},
-            {"job": "install", "package": package_d},
             {"job": "install", "package": package_a},
+            {"job": "install", "package": package_b},
             {"job": "install", "package": package_c},
+            {"job": "install", "package": package_d},
             {"job": "install", "package": package_e},
         ],
     )
 
-    b = ops[0].package
-    c = ops[3].package
-    d = ops[1].package
-    a = ops[2].package
+    a = ops[0].package
+    b = ops[1].package
+    c = ops[2].package
+    d = ops[3].package
     e = ops[4].package
 
     assert d.category == "dev"