Support multi letter sigils in FunctionNames

Refs #1124

lib/credo/check/readability/function_names.ex

@@ -149,8 +149,21 @@ defmodule Credo.Check.Readability.FunctionNames do
     issues
   end
 
-  defp issues_for_name(name, args, meta, issues, issue_meta, allow_acronyms?) do
-    if name |> to_string |> Name.snake_case?(allow_acronyms?) do
+  defp issues_for_name("sigil_" <> sigil_letters = name, args, meta, issues, issue_meta, _allow_acronyms?) do
+    multi_letter_sigil? = String.match?(sigil_letters, ~r/^[A-Z]+$/)
+
+    if multi_letter_sigil? do
+      issues
+    else
+      issue = issue_for(issue_meta, meta[:line], name)
+      arity = length(args || [])
+
+      add_issue(issues, name, arity, issue)
+    end
+  end
+
+  defp issues_for_name("" <> name, args, meta, issues, issue_meta, allow_acronyms?) do
+    if Name.snake_case?(name, allow_acronyms?) do
       issues
     else
       issue = issue_for(issue_meta, meta[:line], name)
@@ -160,6 +173,10 @@ defmodule Credo.Check.Readability.FunctionNames do
     end
   end
 
+  defp issues_for_name(name, args, meta, issues, issue_meta, allow_acronyms?) do
+    name |> to_string |> issues_for_name(args, meta, issues, issue_meta, allow_acronyms?)
+  end
+
   defp issue_for(issue_meta, line_no, trigger) do
     format_issue(
       issue_meta,

test/credo/check/readability/function_names_test.exs

@@ -75,6 +75,23 @@ defmodule Credo.Check.Readability.FunctionNamesTest do
     |> refute_issues()
   end
 
+  test "it should NOT report expected code for multi letter sigils /5" do
+    """
+    def sigil_ZZO(input, args) do
+      # ...
+    end
+    defmacro sigil_ZZU({:<<>>, _, [string]}, []) do
+      # ...
+    end
+    defmacro sigil_ZZU({:<<>>, _, [string]}, []) when is_binary(string) do
+      # ...
+    end
+    """
+    |> to_source_file
+    |> run_check(@described_check)
+    |> refute_issues()
+  end
+
   test "it should NOT report expected code (for operators) /6" do
     """
     defmacro @expr2