From c55c8861cd7a2486c7c674093022e36dd859fd87 Mon Sep 17 00:00:00 2001
From: Ulf Wiger <ulf@feuerlabs.com>
Date: Wed, 19 Dec 2012 17:29:53 +0100
Subject: [PATCH] Added revert_form/1; deal with revert bugs

---
 doc/parse_trans.md  | 27 +++++++++++++++++++++++++--
 src/parse_trans.erl | 22 ++++++++++++++++++++--
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/doc/parse_trans.md b/doc/parse_trans.md
index d68e351..cd99992 100644
--- a/doc/parse_trans.md
+++ b/doc/parse_trans.md
@@ -96,7 +96,7 @@ Performs a transform of <code>Forms</code> using the fun <code>Fun(Form)</code>.
 Reads debug_info from the beam file Beam and returns a string containing
 the pretty-printed corresponding erlang source code.</td></tr><tr><td valign="top"><a href="#pp_beam-2">pp_beam/2</a></td><td>
 Reads debug_info from the beam file Beam and pretty-prints it as
-Erlang source code, storing it in the file Out.</td></tr><tr><td valign="top"><a href="#pp_src-2">pp_src/2</a></td><td>Pretty-prints the erlang source code corresponding to Forms into Out.</td></tr><tr><td valign="top"><a href="#replace_function-4">replace_function/4</a></td><td></td></tr><tr><td valign="top"><a href="#return-2">return/2</a></td><td>Checks the transformed result for errors and warnings.</td></tr><tr><td valign="top"><a href="#revert-1">revert/1</a></td><td>Reverts back from Syntax Tools format to Erlang forms.</td></tr><tr><td valign="top"><a href="#top-3">top/3</a></td><td></td></tr><tr><td valign="top"><a href="#transform-4">transform/4</a></td><td>
+Erlang source code, storing it in the file Out.</td></tr><tr><td valign="top"><a href="#pp_src-2">pp_src/2</a></td><td>Pretty-prints the erlang source code corresponding to Forms into Out.</td></tr><tr><td valign="top"><a href="#replace_function-4">replace_function/4</a></td><td></td></tr><tr><td valign="top"><a href="#return-2">return/2</a></td><td>Checks the transformed result for errors and warnings.</td></tr><tr><td valign="top"><a href="#revert-1">revert/1</a></td><td>Reverts back from Syntax Tools format to Erlang forms.</td></tr><tr><td valign="top"><a href="#revert_form-1">revert_form/1</a></td><td>Reverts a single form back from Syntax Tools format to Erlang forms.</td></tr><tr><td valign="top"><a href="#top-3">top/3</a></td><td></td></tr><tr><td valign="top"><a href="#transform-4">transform/4</a></td><td>
 Makes one pass.</td></tr></table>
 
 
@@ -524,7 +524,30 @@ Reverts back from Syntax Tools format to Erlang forms.
 
 Note that the Erlang forms are a subset of the Syntax Tools
 syntax tree, so this function is safe to call even on a list of
-regular Erlang forms.<a name="top-3"></a>
+regular Erlang forms.<a name="revert_form-1"></a>
+
+###revert_form/1##
+
+
+
+
+<pre>revert_form(F::Tree) -&gt; Form</pre>
+<br></br>
+
+
+
+
+Reverts a single form back from Syntax Tools format to Erlang forms.
+
+
+`erl_syntax:revert/1` has had a long-standing bug where it doesn't
+completely revert attribute forms. This function deals properly with those
+cases.
+
+
+Note that the Erlang forms are a subset of the Syntax Tools
+syntax tree, so this function is safe to call even on a regular Erlang
+form.<a name="top-3"></a>
 
 ###top/3##
 
diff --git a/src/parse_trans.erl b/src/parse_trans.erl
index 3685f83..f2703ef 100644
--- a/src/parse_trans.erl
+++ b/src/parse_trans.erl
@@ -40,6 +40,7 @@
 	 transform/4,
          depth_first/4,
          revert/1,
+	 revert_form/1,
 	 format_exception/2, format_exception/3,
 	 return/2
         ]).
@@ -513,8 +514,25 @@ get_orig_syntax_tree(File) ->
 %%%
 -spec revert(forms()) ->
     forms().
-revert(Tree) ->
-    [erl_syntax:revert(T) || T <- lists:flatten(Tree)].
+revert(Tree) when is_list(Tree) ->
+    [revert_form(T) || T <- lists:flatten(Tree)].
+
+%%% @spec (Tree) -> Form
+%%%
+%%% @doc Reverts a single form back from Syntax Tools format to Erlang forms.
+%%% <p>`erl_syntax:revert/1' has had a long-standing bug where it doesn't
+%%% completely revert attribute forms. This function deals properly with those
+%%% cases.</p>
+%%% <p>Note that the Erlang forms are a subset of the Syntax Tools
+%%% syntax tree, so this function is safe to call even on a regular Erlang
+%%% form.</p>
+revert_form(F) ->
+    case erl_syntax:revert(F) of
+	{attribute,L,A,Tree} when element(1,Tree) == tree ->
+	    {attribute,L,A,erl_syntax:revert(Tree)};
+	Result ->
+	    Result
+    end.
 
 %%% @spec (Forms, Context) -> Forms | {error,Es,Ws} | {warnings,Forms,Ws}
 %%%