Sigil L for safe Slime HTML (#63)

* Initial ~l and ~L macros

* Document

* Test

* Escape the octothorpe so it's included in the docs

* Fix bad test

* Interpolation -> Templating in docs and error msg

lib/phoenix_slime.ex

@@ -1,2 +1,42 @@
 defmodule PhoenixSlime do
+  @doc """
+  Provides the `~l` sigil with HTML safe Slime syntax inside source files.
+
+  Raises on attempts to use `\#{}`. Use `~L` to allow templating with `\#{}`.
+
+      iex> import PhoenixSlime
+      iex> assigns = %{w: "world"}
+      iex> ~l"\""
+      ...> p = "hello " <> @w
+      ...> "\""
+      {:safe, [[["" | "<p>"] | "hello world"] | "</p>"]}
+  """
+  defmacro sigil_l(expr, opts) do
+    handle_sigil(expr, opts, __CALLER__.line)
+  end
+
+  @doc """
+  Provides the `~L` sigil with HTML safe Slime syntax inside source files.
+
+      iex> import PhoenixSlime
+      iex> ~L"\""
+      ...> p hello \#{"world"}
+      ...> "\""
+      {:safe, [[["" | "<p>hello "] | "world" ] | "</p>"]}
+  """
+  defmacro sigil_L(expr, opts) do
+    handle_sigil(expr, opts, __CALLER__.line)
+  end
+
+  defp handle_sigil({:<<>>, _, [expr]}, [], line) do
+    expr
+    |> Slime.Renderer.precompile()
+    |> EEx.compile_string(engine: Phoenix.HTML.Engine, line: line + 1)
+  end
+
+  defp handle_sigil(_, _, _) do
+    raise ArgumentError, ~S(Templating is not allowed with #{} in ~l sigil.) <>
+      ~S( Remove the #{}, use = to insert values, or ) <>
+        ~S(use ~L to template with #{}.)
+  end
 end

test/phoenix_slime_test.exs

@@ -1,6 +1,7 @@
 defmodule PhoenixSlimeTest do
   use ExUnit.Case
   alias Phoenix.View
+  doctest PhoenixSlime
 
   defmodule MyApp.PageView do
     use Phoenix.View, root: "test/fixtures/templates"