installer.py: traverse_dependencies has local deptype (#33367)

Currently `traverse_dependencies` fixes deptypes to traverse once and
for all in the recursion, but this is incorrect, since deptypes depend
on the node (e.g. if it's a dependency and cache-only, don't follow
build type edges, even if the parent is build from sources and needs
build deps.)

lib/spack/spack/installer.py

@@ -2426,21 +2426,31 @@ def spec(self):
         """The specification associated with the package."""
         return self.pkg.spec
 
-    def traverse_dependencies(self):
+    def traverse_dependencies(self, spec=None, visited=None):
         """
         Yield any dependencies of the appropriate type(s)
 
         Yields:
             (Spec) The next child spec in the DAG
         """
-        get_spec = lambda s: s.spec
+        # notice: deptype is not constant across nodes, so we cannot use
+        # spec.traverse_edges(deptype=...).
 
-        deptypes = self.get_deptypes(self.pkg)
-        tty.debug("Processing dependencies for {0}: {1}".format(self.pkg_id, deptypes))
-        for dspec in self.spec.traverse_edges(
-            deptype=deptypes, order="post", root=False, direction="children"
-        ):
-            yield get_spec(dspec)
+        if spec is None:
+            spec = self.spec
+        if visited is None:
+            visited = set()
+        deptype = self.get_deptypes(spec.package)
+
+        for dep in spec.dependencies(deptype=deptype):
+            hash = dep.dag_hash()
+            if hash in visited:
+                continue
+            visited.add(hash)
+            # In Python 3: yield from self.traverse_dependencies(dep, visited)
+            for s in self.traverse_dependencies(dep, visited):
+                yield s
+            yield dep
 
 
 class InstallError(spack.error.SpackError):