Cache scope priorities

lib/credo/application.ex

@@ -8,6 +8,7 @@ defmodule Credo.Application do
     Credo.Service.SourceFileAST,
     Credo.Service.SourceFileLines,
     Credo.Service.SourceFileScopes,
+    Credo.Service.SourceFileScopePriorities,
     Credo.Service.SourceFileSource
   ]
 

lib/credo/check.ex

@@ -171,6 +171,7 @@ defmodule Credo.Check do
     warning: 16
   }
 
+  alias Credo.Service.SourceFileScopePriorities
   alias Credo.Check
   alias Credo.Check.Params
   alias Credo.Code.Scope
@@ -759,7 +760,18 @@ defmodule Credo.Check do
   end
 
   defp priority_for(source_file, scope) do
-    scope_prio_map = Priority.scope_priorities(source_file)
+    # Caching scope priorities, because these have to be computed only once per file. This
+    # significantly speeds up the execution time when a large number of issues are generated.
+    scope_prio_map =
+      case SourceFileScopePriorities.get(source_file) do
+        {:ok, value} ->
+          value
+
+        :notfound ->
+          result = Priority.scope_priorities(source_file)
+          SourceFileScopePriorities.put(source_file, result)
+          result
+      end
 
     scope_prio_map[scope] || 0
   end

lib/credo/service/source_file_scope_priorities.ex

@@ -0,0 +1,5 @@
+defmodule Credo.Service.SourceFileScopePriorities do
+  @moduledoc false
+
+  use Credo.Service.ETSTableHelper
+end