Extract valid_chain_start?/3 pipe helper function into helper module

Author: Stratus3D

lib/credo/check/pipe_helpers.ex

@@ -0,0 +1,232 @@
+defmodule Credo.Check.PipeHelpers do
+  @elixir_custom_operators [
+    :<-,
+    :|||,
+    :&&&,
+    :<<<,
+    :>>>,
+    :<<~,
+    :~>>,
+    :<~,
+    :~>,
+    :<~>,
+    :"<|>",
+    :"^^^",
+    :"~~~",
+    :"..//"
+  ]
+
+  def valid_chain_start?(
+         {:__block__, _, [single_ast_node]},
+         excluded_functions,
+         excluded_argument_types
+       ) do
+    valid_chain_start?(
+      single_ast_node,
+      excluded_functions,
+      excluded_argument_types
+    )
+  end
+
+  for atom <- [
+        :%,
+        :%{},
+        :..,
+        :<<>>,
+        :@,
+        :__aliases__,
+        :unquote,
+        :{},
+        :&,
+        :<>,
+        :++,
+        :--,
+        :&&,
+        :||,
+        :+,
+        :-,
+        :*,
+        :/,
+        :>,
+        :>=,
+        :<,
+        :<=,
+        :==,
+        :for,
+        :with,
+        :not,
+        :and,
+        :or
+      ] do
+    def valid_chain_start?(
+           {unquote(atom), _meta, _arguments},
+           _excluded_functions,
+           _excluded_argument_types
+         ) do
+      true
+    end
+  end
+
+  for operator <- @elixir_custom_operators do
+    def valid_chain_start?(
+           {unquote(operator), _meta, _arguments},
+           _excluded_functions,
+           _excluded_argument_types
+         ) do
+      true
+    end
+  end
+
+  # anonymous function
+  def valid_chain_start?(
+         {:fn, _, [{:->, _, [_args, _body]}]},
+         _excluded_functions,
+         _excluded_argument_types
+       ) do
+    true
+  end
+
+  # function_call()
+  def valid_chain_start?(
+         {atom, _, []},
+         _excluded_functions,
+         _excluded_argument_types
+       )
+       when is_atom(atom) do
+    true
+  end
+
+  # function_call(with, args) and sigils
+  def valid_chain_start?(
+         {atom, _, arguments} = ast,
+         excluded_functions,
+         excluded_argument_types
+       )
+       when is_atom(atom) and is_list(arguments) do
+    sigil?(atom) ||
+      valid_chain_start_function_call?(
+        ast,
+        excluded_functions,
+        excluded_argument_types
+      )
+  end
+
+  # map[:access]
+  def valid_chain_start?(
+         {{:., _, [Access, :get]}, _, _},
+         _excluded_functions,
+         _excluded_argument_types
+       ) do
+    true
+  end
+
+  # Module.function_call()
+  def valid_chain_start?(
+         {{:., _, _}, _, []},
+         _excluded_functions,
+         _excluded_argument_types
+       ),
+       do: true
+
+  # Elixir <= 1.8.0
+  # '__#{val}__' are compiled to String.to_charlist("__#{val}__")
+  # we want to consider these charlists a valid pipe chain start
+  def valid_chain_start?(
+         {{:., _, [String, :to_charlist]}, _, [{:<<>>, _, _}]},
+         _excluded_functions,
+         _excluded_argument_types
+       ),
+       do: true
+
+  # Elixir >= 1.8.0
+  # '__#{val}__' are compiled to String.to_charlist("__#{val}__")
+  # we want to consider these charlists a valid pipe chain start
+  def valid_chain_start?(
+         {{:., _, [List, :to_charlist]}, _, [[_ | _]]},
+         _excluded_functions,
+         _excluded_argument_types
+       ),
+       do: true
+
+  # Module.function_call(with, parameters)
+  def valid_chain_start?(
+         {{:., _, _}, _, _} = ast,
+         excluded_functions,
+         excluded_argument_types
+       ) do
+    valid_chain_start_function_call?(
+      ast,
+      excluded_functions,
+      excluded_argument_types
+    )
+  end
+
+  def valid_chain_start?(_, _excluded_functions, _excluded_argument_types), do: true
+
+  def valid_chain_start_function_call?(
+         {_atom, _, arguments} = ast,
+         excluded_functions,
+         excluded_argument_types
+       ) do
+    function_name = to_function_call_name(ast)
+
+    found_argument_types =
+      case arguments do
+        [nil | _] -> [:atom]
+        x -> x |> List.first() |> argument_type()
+      end
+
+    Enum.member?(excluded_functions, function_name) ||
+      Enum.any?(
+        found_argument_types,
+        &Enum.member?(excluded_argument_types, &1)
+      )
+  end
+
+  defp sigil?(atom) do
+    atom
+    |> to_string
+    |> String.match?(~r/^sigil_[a-zA-Z]$/)
+  end
+
+  defp to_function_call_name({_, _, _} = ast) do
+    {ast, [], []}
+    |> Macro.to_string()
+    |> String.replace(~r/\.?\(.*\)$/s, "")
+  end
+
+  @alphabet_wo_r ~w(a b c d e f g h i j k l m n o p q s t u v w x y z)
+  @all_sigil_chars Enum.flat_map(@alphabet_wo_r, &[&1, String.upcase(&1)])
+  @matchable_sigils Enum.map(@all_sigil_chars, &:"sigil_#{&1}")
+
+  for sigil_atom <- @matchable_sigils do
+    defp argument_type({unquote(sigil_atom), _, _}) do
+      [unquote(sigil_atom)]
+    end
+  end
+
+  defp argument_type({:sigil_r, _, _}), do: [:sigil_r, :regex]
+  defp argument_type({:sigil_R, _, _}), do: [:sigil_R, :regex]
+
+  defp argument_type({:fn, _, _}), do: [:fn]
+  defp argument_type({:%{}, _, _}), do: [:map]
+  defp argument_type({:{}, _, _}), do: [:tuple]
+  defp argument_type(nil), do: []
+
+  defp argument_type(v) when is_atom(v), do: [:atom]
+  defp argument_type(v) when is_binary(v), do: [:binary]
+  defp argument_type(v) when is_bitstring(v), do: [:bitstring]
+  defp argument_type(v) when is_boolean(v), do: [:boolean]
+
+  defp argument_type(v) when is_list(v) do
+    if Keyword.keyword?(v) do
+      [:keyword, :list]
+    else
+      [:list]
+    end
+  end
+
+  defp argument_type(v) when is_number(v), do: [:number]
+
+  defp argument_type(v), do: [:credo_type_error, v]
+end