fix: resolves the JSON error when no match is found by comby (fixes #29) (#30)

Author: jrfaller

src/comby/binary.py

@@ -103,10 +103,11 @@ def matches(self,
                shlex.quote(template), 'foo')
         cmd_s = ' '.join(cmd)
 
-        jsn = json.loads(self.call(cmd_s, text=source))
-        jsn = jsn['matches']
-        for jsn_match in jsn:
-            yield Match.from_dict(jsn_match)
+        jsn = json.loads(self.call(cmd_s, text=source) or 'null')
+        if jsn is not None:
+            jsn = jsn['matches']
+            for jsn_match in jsn:
+                yield Match.from_dict(jsn_match)
 
     def rewrite(self,
                 source: str,

test/test_binary.py

@@ -18,6 +18,12 @@ def test_match(comby):
     assert len(matches) == 1
     print(matches[0])
 
+def test_no_match(comby):
+    source = "foo"
+    template = "bar"
+    matches = list(comby.matches(source, template))
+    print(matches)
+    assert len(matches) == 0
 
 def test_rewrite(comby):
     source = "print('hello world')"