Add Django and html singleton tags support to pretty print.

In this commit we are modifying pretty print tool to support
Django and html singleton tags. For Addition of html singleton
tags template parser was modified to emit psudeo
html singleton end tags to accompany html singleton tags and
token class was updated to have line_span field.

tools/lib/template_parser.py

@@ -27,13 +27,14 @@ class TokenizerState(object):
         self.col = 1
 
 class Token(object):
-    def __init__(self, kind, s, tag, line, col):
-        # type: (str, str, str, int, int) -> None
+    def __init__(self, kind, s, tag, line, col, line_span):
+        # type: (str, str, str, int, int, int) -> None
         self.kind = kind
         self.s = s
         self.tag = tag
         self.line = line
         self.col = col
+        self.line_span = line_span
 
 def tokenize(text):
     # type: (str) -> List[Token]
@@ -131,15 +132,30 @@ def tokenize(text):
                                           (e.message, state.line, state.col,
                                            e.line_content))
 
+        line_span = len(s.split('\n'))
         token = Token(
             kind=kind,
             s=s,
             tag=tag,
             line=state.line,
             col=state.col,
+            line_span=line_span
         )
         tokens.append(token)
         advance(len(s))
+        if kind == 'html_singleton':
+            # Here we insert a Pseudo html_singleton_end tag so as to have
+            # ease of detection of end of singleton html tags which might be
+            # needed in some cases as with our html pretty printer.
+            token = Token(
+                kind='html_singleton_end',
+                s='</' + tag + '>',
+                tag=tag,
+                line=state.line,
+                col=state.col,
+                line_span=1
+            )
+            tokens.append(token)
 
     return tokens