unit tests: Test more syntax highlighting data

@TingPing has a repository that contains a grammar for meson which is
used by linguist (GitHub), and by many editors such as Atom, VS Code,
TextMate, Sublime Text, etc. Add CI so that we notice that the
function list in it is out of date, such as https://github.com/TingPing/language-meson/pull/3

It's harder to do this generically for other syntax such as the `in`
keyword, but it's better than nothing.

run_unittests.py

@@ -30,6 +30,8 @@ import functools
 import io
 import operator
 import threading
+import urllib.error
+import urllib.request
 from itertools import chain
 from unittest import mock
 from configparser import ConfigParser
@@ -1126,10 +1128,10 @@ class DataTests(unittest.TestCase):
             if f not in exceptions:
                 self.assertIn(f, toc)
 
-    def test_syntax_highlighting_files(self):
+    def test_vim_syntax_highlighting(self):
         '''
-        Ensure that syntax highlighting files were updated for new functions in
-        the global namespace in build files.
+        Ensure that vim syntax highlighting files were updated for new
+        functions in the global namespace in build files.
         '''
         env = get_fake_env()
         interp = Interpreter(FakeBuild(env), mock=True)
@@ -1138,6 +1140,39 @@ class DataTests(unittest.TestCase):
             defined = set([a.strip() for a in res.group().split('\\')][1:])
             self.assertEqual(defined, set(chain(interp.funcs.keys(), interp.builtin.keys())))
 
+    def test_json_grammar_syntax_highlighting(self):
+        '''
+        Ensure that syntax highlighting JSON grammar written by TingPing was
+        updated for new functions in the global namespace in build files.
+        https://github.com/TingPing/language-meson/
+        '''
+        env = get_fake_env()
+        interp = Interpreter(FakeBuild(env), mock=True)
+        url = 'https://raw.githubusercontent.com/TingPing/language-meson/master/grammars/meson.json'
+        try:
+            r = urllib.request.urlopen(url)
+        except urllib.error.URLError as e:
+            # Skip test when network is not available, such as during packaging
+            # by a distro or Flatpak
+            if not isinstance(e, urllib.error.HTTPError):
+                raise unittest.SkipTest('Network unavailable')
+            # Don't fail the test if github is down, but do fail if 4xx
+            if e.code >= 500:
+                raise unittest.SkipTest('Server error ' + str(e.code))
+            raise e
+        # On Python 3.5, we must decode bytes to string. Newer versions don't require that.
+        grammar = json.loads(r.read().decode('utf-8', 'surrogatepass'))
+        for each in grammar['patterns']:
+            if 'name' in each and each['name'] == 'support.function.builtin.meson':
+                # The string is of the form: (?x)\\b(func1|func2|...\n)\\b\\s*(?=\\() and
+                # we convert that to [func1, func2, ...] without using regex to parse regex
+                funcs = set(each['match'].split('\\b(')[1].split('\n')[0].split('|'))
+            if 'name' in each and each['name'] == 'support.variable.meson':
+                # \\b(builtin1|builtin2...)\\b
+                builtin = set(each['match'].split('\\b(')[1].split(')\\b')[0].split('|'))
+        self.assertEqual(builtin, set(interp.builtin.keys()))
+        self.assertEqual(funcs, set(interp.funcs.keys()))
+
     def test_all_functions_defined_in_ast_interpreter(self):
         '''
         Ensure that the all functions defined in the Interpreter are also defined