Support enabling check via {Credo.Check.*, true}

.credo.exs

@@ -64,6 +64,10 @@
       #
       #     {Credo.Check.Design.DuplicatedCode, false}
       #
+      # To enable a check with default params put `true` or `[]` as second element:
+      #
+      #     {Credo.Check.Readability.StrictModuleLayout, true}
+      #
       checks: %{
         enabled: [
           #

guides/configuration/check_params.md

@@ -45,6 +45,12 @@ All checks are configured using a two-element tuple:
 {Credo.Check.Design.AliasUsage, if_nested_deeper_than: 2}
 ```
 
+Passing `true` is equivalent to passing an empty list of parameters:
+
+```elixir
+{Credo.Check.Readability.StrictModuleLayout, true}
+```
+
 ## General params
 
 While `params` are defined by each check individually, there are a couple of general params provided by Credo, which work the same for each check.

lib/credo/config_file.ex

@@ -388,11 +388,12 @@ defmodule Credo.ConfigFile do
         checks: %{enabled: checks_other_enabled} = checks_other
       })
       when is_list(checks_other_enabled) do
-    disabled = disable_check_tuples(checks_other[:disabled])
+    other_disabled = normalize_check_tuples(checks_other[:disabled])
+    disabled = disable_check_tuples(other_disabled)
 
     %{
       enabled: checks_other_enabled |> normalize_check_tuples() |> Keyword.merge(disabled),
-      disabled: checks_other[:disabled] || []
+      disabled: other_disabled
     }
   end
 
@@ -426,7 +427,9 @@ defmodule Credo.ConfigFile do
   end
 
   def merge_checks(base, other) when is_list(base) and is_list(other) do
-    Keyword.merge(base, other)
+    base
+    |> normalize_check_tuples()
+    |> Keyword.merge(normalize_check_tuples(other))
   end
 
   #
@@ -445,6 +448,7 @@ defmodule Credo.ConfigFile do
   end
 
   defp normalize_check_tuple({name}), do: {name, []}
+  defp normalize_check_tuple({name, true}), do: {name, []}
   defp normalize_check_tuple(tuple), do: tuple
 
   defp disable_check_tuples(nil), do: []

test/credo/config_file_test.exs

@@ -562,6 +562,87 @@
            ]
   end
 
+  test "merge_checks treats true as default params" do
+    base = %ConfigFile{
+      checks: %{
+        enabled: [
+          {Credo.Check.Consistency.ExceptionNames, []},
+          {Credo.Check.Consistency.LineEndings, []}
+        ],
+        disabled: [
+          {Credo.Check.Readability.StrictModuleLayout, []}
+        ]
+      }
+    }
+
+    other = %ConfigFile{
+      checks: %{
+        enabled: [
+          {Credo.Check.Readability.StrictModuleLayout, true}
+        ]
+      }
+    }
+
+    expected = %{
+      enabled: [
+        {Credo.Check.Readability.StrictModuleLayout, []}
+      ],
+      disabled: []
+    }
+
+    assert_sorted_equality(expected, ConfigFile.merge_checks(base, other))
+  end
+
+  test "merge_checks treats true as default params for disabled checks" do
+    base = %ConfigFile{
+      checks: %{
+        enabled: [
+          {Credo.Check.Consistency.ExceptionNames, []}
+        ]
+      }
+    }
+
+    other = %ConfigFile{
+      checks: %{
+        enabled: [
+          {Credo.Check.Consistency.LineEndings, []}
+        ],
+        disabled: [
+          {Credo.Check.Readability.StrictModuleLayout, true}
+        ]
+      }
+    }
+
+    expected = %{
+      enabled: [
+        {Credo.Check.Consistency.LineEndings, []},
+        {Credo.Check.Readability.StrictModuleLayout, false}
+      ],
+      disabled: [
+        {Credo.Check.Readability.StrictModuleLayout, []}
+      ]
+    }
+
+    assert_sorted_equality(expected, ConfigFile.merge_checks(base, other))
+  end
+
+  test "merge_checks treats true as default params when merging check lists" do
+    base = [
+      {Credo.Check.Consistency.ExceptionNames, []},
+      {Credo.Check.Consistency.LineEndings, true}
+    ]
+
+    other = [
+      {Credo.Check.Readability.StrictModuleLayout, true}
+    ]
+
+    assert ConfigFile.merge_checks(base, other) == [
+             {Credo.Check.Consistency.ExceptionNames, []},
+             {Credo.Check.Consistency.LineEndings, []},
+             {Credo.Check.Readability.StrictModuleLayout, []}
+           ]
+  end
+
   test "loads .credo.exs from ./config subdirs in ascending directories as well" do
     dirs = ConfigFile.relevant_directories(".")