hmm hmm hmm

lib/style/module_directives.ex

@@ -73,6 +73,17 @@ defmodule Styler.Style.ModuleDirectives do
   @attr_directives ~w(moduledoc shortdoc behaviour)a ++ @callback_attrs
   @defstruct ~w(schema embedded_schema defstruct)a
 
+  # taken from Credo
+  @excluded_namespaces MapSet.new(~w(File IO Inspect Kernel Macro Supervisor Task Version)a)
+  @stdlib MapSet.new(~w(Access Agent Application Atom Base Behaviour
+                    Bitwise Code Date DateTime Dict Enum Exception
+                    File Float GenEvent GenServer HashDict HashSet
+                    Integer IO Kernel Keyword List Macro Map MapSet
+                    Module NaiveDateTime Node OptionParser Path Port
+                    Process Protocol Range Record Regex Registry Set
+                    Stream String StringIO Supervisor System Task Time
+                    Tuple URI Version)a)
+
   @moduledoc_false {:@, [line: nil], [{:moduledoc, [line: nil], [{:__block__, [line: nil], [false]}]}]}
 
   def run({{:defmodule, _, children}, _} = zipper, ctx) do
@@ -183,10 +194,78 @@ defmodule Styler.Style.ModuleDirectives do
 
     uses = (directives[:use] || []) |> Enum.flat_map(&expand_directive/1) |> reset_newlines()
     imports = expand_and_sort(directives[:import] || [])
-    requires = expand_and_sort(directives[:require] || [])
+
     all_aliases = directives[:alias] || []
     aliases = expand_and_sort(all_aliases)
 
+    aliased =
+      aliases
+      |> Enum.flat_map(fn
+        {:alias, _, [{:__aliases__, _, aliases}]} -> [aliases]
+        _ -> []
+      end)
+      |> MapSet.new(&List.last/1)
+
+    excluded_first = MapSet.union(aliased, @excluded_namespaces)
+    excluded_last = MapSet.union(aliased, @stdlib)
+
+    to_alias =
+      nondirectives
+      |> Zipper.zip()
+      |> Zipper.traverse_while(%{}, fn
+        # Credo doesn't look at :@ nodes. I kinda like it? especially for typespecs.
+        {{directive, _, _}, _} = zipper, acc when directive in ~w(@ use)a ->
+          {:skip, zipper, acc}
+
+        # A.B.C
+        {{:__aliases__, _, [first, _, _ | _] = aliases}, _} = zipper, acc ->
+          last = List.last(aliases)
+          acc =
+            if last in excluded_last or first in excluded_first,
+              do: acc,
+              else: Map.update(acc, aliases, false, fn _ -> true end)
+
+          {:skip, zipper, acc}
+
+        zipper, acc ->
+          {:cont, zipper, acc}
+      end)
+      |> elem(1)
+      # if we have `Foo.Bar.Baz` and `Foo.Bar.Bop.Baz` both not aliased, we'll create a collision by extracting both.
+      # grouping by last alias lets us detect these collisions
+      |> Enum.group_by(fn {aliases, _} -> List.last(aliases) end)
+      |> Enum.filter(fn
+        # only extract if it doesn't conflict and was used more than once
+        {_, [{_, true}]} -> true
+        _ -> false
+      end)
+      |> MapSet.new(fn {_, [{aliases, _}]} -> aliases end)
+
+    replace_new_aliases = fn
+      {{:__aliases__, meta, [_, _, _ | _] = aliases}, z_meta} = zipper ->
+        if aliases in to_alias, do: {{:__aliases__, meta, [List.last(aliases)]}, z_meta}, else: zipper
+
+      zipper ->
+        zipper
+    end
+
+    # @TODO bug here if the first line of the parent is a comment
+    # diff:
+    #     """
+    #     -
+    #     -  # a comment on use
+    #     use Ecto.Type
+    #
+    #     +  alias Some.Long.Alias
+    #     +
+    #     +  # a comment on use
+    aliases =
+      expand_and_sort(
+        aliases ++ Enum.map(to_alias, &{:alias, [line: 0], [{:__aliases__, [last: [line: 0], line: 0], &1}]})
+      )
+
+    requires = expand_and_sort(directives[:require] || []) |> Zipper.zip() |> Zipper.traverse(replace_new_aliases) |> Zipper.node()
+
     directives =
       [
         shortdocs,
@@ -209,6 +288,8 @@ defmodule Styler.Style.ModuleDirectives do
         Zipper.update(parent, &Zipper.replace_children(&1, directives))
 
       true ->
+        nondirectives = nondirectives |> Zipper.zip() |> Zipper.traverse(replace_new_aliases) |> Zipper.node()
+
         parent
         |> Zipper.update(&Zipper.replace_children(&1, directives))
         |> Zipper.down()