improvement: add copy_template/4

lib/igniter.ex

@@ -412,7 +412,18 @@ defmodule Igniter do
     )
   end
 
-  @doc "Creates a new (non-elixir) file in the project with the provided string contents. Adds an error if it already exists."
+  @spec copy_template(
+          igniter :: Igniter.t(),
+          target :: Path.t(),
+          source :: Path.t(),
+          assigns :: Keyword.t()
+        ) :: Igniter.t()
+  def copy_template(igniter, source, target, assigns) do
+    contents = EEx.eval_file(source, assigns: assigns)
+    create_new_file(igniter, target, contents)
+  end
+
+  @doc "Creates a new file in the project with the provided string contents. Adds an error if it already exists."
   @spec create_new_file(t(), Path.t(), String.t()) :: Igniter.t()
   def create_new_file(igniter, path, contents \\ "", opts \\ []) do
     source_handler = source_handler(path, opts)

test/igniter_test.exs

@@ -1,4 +1,22 @@
 defmodule IgniterTest do
   use ExUnit.Case
   doctest Igniter
+
+  describe "Igniter.copy_template/4" do
+    test "it evaluates and writes the template" do
+      %{rewrite: rewrite} =
+        Igniter.new()
+        |> Igniter.copy_template("test/templates/template.css.eex", "lib/foobar.css",
+          class: "hello"
+        )
+
+      config_file = Rewrite.source!(rewrite, "lib/foobar.css")
+
+      assert Rewrite.Source.get(config_file, :content) == """
+             .hello {
+                background: black
+             }
+             """
+    end
+  end
 end

test/templates/template.css.eex

@@ -0,0 +1,3 @@
+.<%= @class %> {
+   background: black
+}