Make fn param optional with template_parser.validate().

The caller can now pass in text directly.  This is mostly for
testing, but it could be useful in other situations.

tools/check-templates

@@ -85,7 +85,7 @@ def check_html_templates(templates, modified_only):
             'templates/zerver/right-sidebar.html',
             'templates/zerver/search_operators.html',
         ]
-        validate(fn, check_indent=(fn not in bad_files))
+        validate(fn=fn, check_indent=(fn not in bad_files))
 
 def check_handlebar_templates(templates, modified_only):
     # type: (Iterable[str], bool) -> None
@@ -94,7 +94,7 @@ def check_handlebar_templates(templates, modified_only):
     if not modified_only:
         assert len(templates) >= 10 # sanity check that we are actually doing work
     for fn in templates:
-        validate(fn, check_indent=True)
+        validate(fn=fn, check_indent=True)
 
 if __name__ == '__main__':
     check_our_files()

tools/lib/template_parser.py

@@ -103,9 +103,16 @@ def tokenize(text):
 
     return tokens
 
-def validate(fn, check_indent=True):
-    # type: (str, bool) -> None
-    text = open(fn).read()
+def validate(fn=None, text=None, check_indent=True):
+    # type: (str, str, bool) -> None
+    assert fn or text
+
+    if fn is None:
+        fn = '<in memory file>'
+
+    if text is None:
+        text = open(fn).read()
+
     tokens = tokenize(text)
 
     class State(object):