Restrict `blocktrans` content to only strings and plain variables. #88

This matches Django behaviour.

src/erlydtl_parser.yrl

@@ -113,6 +113,7 @@ Nonterminals
     SSITag
 
     BlockTransBlock
+    BlockTransContent
     TransTag    
 
     TemplatetagTag
@@ -367,8 +368,12 @@ SpacelessBlock -> open_tag spaceless_keyword close_tag Elements open_tag endspac
 SSITag -> open_tag ssi_keyword Value close_tag : {ssi, '$3'}.
 SSITag -> open_tag ssi_keyword string_literal parsed_keyword close_tag : {ssi_parsed, '$3'}.
 
-BlockTransBlock -> open_tag blocktrans_keyword close_tag Elements open_tag endblocktrans_keyword close_tag : {blocktrans, [], '$4'}.
-BlockTransBlock -> open_tag blocktrans_keyword with_keyword Args close_tag Elements open_tag endblocktrans_keyword close_tag : {blocktrans, '$4', '$6'}.
+BlockTransBlock -> open_tag blocktrans_keyword close_tag BlockTransContent open_tag endblocktrans_keyword close_tag : {blocktrans, [], '$4'}.
+BlockTransBlock -> open_tag blocktrans_keyword with_keyword Args close_tag BlockTransContent open_tag endblocktrans_keyword close_tag : {blocktrans, '$4', '$6'}.
+BlockTransContent -> '$empty' : [].
+BlockTransContent -> BlockTransContent open_var identifier close_var : '$1' ++ [{variable, '$3'}].
+BlockTransContent -> BlockTransContent string : '$1' ++ ['$2'].
+%% TODO: {% plural %}
 
 TemplatetagTag -> open_tag templatetag_keyword Templatetag close_tag : {templatetag, '$3'}.
 

tests/src/erlydtl_unittests.erl

@@ -1191,6 +1191,8 @@ tests() ->
         [{blocktrans_locales, ["de"]}, {blocktrans_fun, fun("Hello, {{ name }}", "de") -> <<"Guten tag, {{ name }}">> end}], <<"Guten tag, Mr. President">>},
        {"blocktrans with args",
         <<"{% blocktrans with var1=foo %}{{ var1 }}{% endblocktrans %}">>, [{foo, "Hello"}], <<"Hello">>}
+       %% {"blocktrans complex not allowed",
+       %%  <<"{% blocktrans %}Hello{%if user%}, {{ user.name }}{%endif%}!{% endblocktrans %}">>, [], assert-raise-syntax-error}
       ]},
      {"verbatim", [
                    {"Plain verbatim",