Issue 6877 - Only parse headers in the first line of the filter list

tests/test_parser.py

 # This file is part of Adblock Plus <https://adblockplus.org/>,
 # Copyright (C) 2006-present eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ skipping 140 matching lines @@
     line = parse_line('%include foo:bar/baz.txt%')
     assert line.type == 'include'
     assert line.target == 'foo:bar/baz.txt'
 
 
 def test_parse_bad_instruction():
     with pytest.raises(ParseError):
         parse_line('%foo bar%')
 
 
-def test_parse_bad_header():
+def test_parse_start():
+    # Header-line lines are headers.
+    assert parse_line('[Adblock Plus 1.1]', mode='start').type == 'header'
+    # But space is not allowed in headers.
+    assert parse_line(' [Adblock Plus 1.1]', mode='start').type == 'filter'
+    assert parse_line('[Adblock Plus 1.1] ', mode='start').type == 'filter'
+
     with pytest.raises(ParseError):
-        parse_line('[Adblock 1.1]')
+        # Invalid headers cause exceptions.
+        parse_line('[Adblock 1.1]', mode='start')
+
+    # Metadata-like lines are metadata.
+    assert parse_line('! Foo: bar', mode='metadata').type == 'metadata'
+
+
+def test_parse_metadata():
+    # Header-like lines are just filters.
+    assert parse_line('[Adblock 1.1]', mode='metadata').type == 'filter'
+    # Metadata-like lines are metadata.
+    assert parse_line('! Foo: bar', mode='metadata').type == 'metadata'
+
+
+def test_parse_body():
+    # Header-like lines are just filters.
+    assert parse_line('[Adblock 1.1]', mode='body').type == 'filter'
+    # Metadata-like lines are comments.
+    assert parse_line('! Foo: bar', mode='body').type == 'comment'
+    # But there's an exception for the checksum.
+    assert parse_line('! Checksum: 42', mode='body').type == 'metadata'
+
+
+def test_parse_invalid_mode():
+    with pytest.raises(ValueError):
+        parse_line('', mode='nonsense')
 
 
 def test_parse_filterlist():
     result = parse_filterlist(['[Adblock Plus 1.1]',
-                               '! Last modified: 26 Jul 2018 02:10 UTC',
+                               ' ! Last modified: 26 Jul 2018 02:10 UTC ',
                                '! Homepage  :  http://aaa.com/b',
                                '||example.com^',
                                '! Checksum: OaopkIiiAl77sSHk/VAWDA',
                                '! Note: bla bla'])
 
     assert next(result) == Header('Adblock Plus 1.1')
-    assert next(result) == Metadata('Last modified', '26 Jul 2018 02:10 UTC')
+    # Check that trailing space is not stripped (like in ABP).
+    assert next(result) == Metadata('Last modified', '26 Jul 2018 02:10 UTC ')
     assert next(result) == Metadata('Homepage', 'http://aaa.com/b')
     assert next(result).type == 'filter'
     assert next(result) == Metadata('Checksum', 'OaopkIiiAl77sSHk/VAWDA')
     assert next(result).type == 'comment'
 
     with pytest.raises(StopIteration):
         next(result)
 
 
 def test_exception_timing():
     result = parse_filterlist(['! good line', '%bad line%'])
     assert next(result) == Comment('good line')
     with pytest.raises(ParseError):
         next(result)
 
 
 def test_parse_line_bytes():
     line = parse_line(b'! \xc3\xbc')
     assert line.text == '\xfc'