Improve error message for oneOf and anyOf

fastjsonschema/draft04.py

@@ -158,7 +158,7 @@ def generate_any_of(self):
                 self.l('except JsonSchemaValueException: pass')
 
         with self.l('if not {variable}_any_of_count{count}:', count=count, optimize=False):
-            self.exc('{name} must be valid by one of anyOf definition', rule='anyOf')
+            self.exc('{name} cannot be validated by any definition', rule='anyOf')
 
     def generate_one_of(self):
         """
@@ -188,7 +188,8 @@ def generate_one_of(self):
                 self.l('except JsonSchemaValueException: pass')
 
         with self.l('if {variable}_one_of_count{count} != 1:', count=count):
-            self.exc('{name} must be valid exactly by one of oneOf definition', rule='oneOf')
+            dynamic = '" (" + str({variable}_one_of_count{}) + " matches found)"'
+            self.exc('{name} must be valid exactly by one definition', count, append_to_msg=dynamic, rule='oneOf')
 
     def generate_not(self):
         """

fastjsonschema/generator.py

@@ -247,11 +247,14 @@ def e(self, string):
         """
         return str(string).replace('"', '\\"')
 
-    def exc(self, msg, *args, rule=None):
+    def exc(self, msg, *args, append_to_msg=None, rule=None):
         """
         Short-cut for creating raising exception in the code.
         """
-        msg = 'raise JsonSchemaValueException("'+msg+'", value={variable}, name="{name}", definition={definition}, rule={rule})'
+        arg = '"'+msg+'"'
+        if append_to_msg:
+            arg += ' + (' + append_to_msg + ')'
+        msg = 'raise JsonSchemaValueException('+arg+', value={variable}, name="{name}", definition={definition}, rule={rule})'
         definition = self._expand_refs(self._definition)
         definition_rule = self.e(definition.get(rule) if isinstance(definition, dict) else None)
         self.l(msg, *args, definition=repr(definition), rule=repr(rule), definition_rule=definition_rule)

tests/test_common.py

@@ -39,7 +39,7 @@ def test_all_of(asserter, value, expected):
     ]}, value, expected)
 
 
-exc = JsonSchemaValueException('data must be valid by one of anyOf definition', value='{data}', name='data', definition='{definition}', rule='anyOf')
+exc = JsonSchemaValueException('data cannot be validated by any definition', value='{data}', name='data', definition='{definition}', rule='anyOf')
 @pytest.mark.parametrize('value, expected', [
     (0, 0),
     (None, exc),
@@ -55,13 +55,16 @@ def test_any_of(asserter, value, expected):
     ]}, value, expected)
 
 
-exc = JsonSchemaValueException('data must be valid exactly by one of oneOf definition', value='{data}', name='data', definition='{definition}', rule='oneOf')
+def exc(n):
+    suffix = " ({} matches found)".format(n)
+    return JsonSchemaValueException('data must be valid exactly by one definition' + suffix, value='{data}', name='data', definition='{definition}', rule='oneOf')
+
 @pytest.mark.parametrize('value, expected', [
-    (0, exc),
-    (2, exc),
+    (0, exc(2)),
+    (2, exc(0)),
     (9, 9),
     (10, 10),
-    (15, exc),
+    (15, exc(2)),
 ])
 def test_one_of(asserter, value, expected):
     asserter({'oneOf': [
@@ -70,13 +73,12 @@ def test_one_of(asserter, value, expected):
     ]}, value, expected)
 
 
-exc = JsonSchemaValueException('data must be valid exactly by one of oneOf definition', value='{data}', name='data', definition='{definition}', rule='oneOf')
 @pytest.mark.parametrize('value, expected', [
-    (0, exc),
-    (2, exc),
+    (0, exc(2)),
+    (2, exc(0)),
     (9, 9),
     (10, 10),
-    (15, exc),
+    (15, exc(2)),
 ])
 def test_one_of_factorized(asserter, value, expected):
     asserter({

tests/test_integration.py

@@ -98,7 +98,7 @@
     ),
     (
         [9, 'hello', [1], {'a': 'a', 'b': 'b', 'x': 'x'}, 42, 15],
-        JsonSchemaValueException('data[5] must be valid exactly by one of oneOf definition', value=15, name='data[5]', definition=definition['items'][5], rule='oneOf'),
+        JsonSchemaValueException('data[5] must be valid exactly by one definition (2 matches found)', value=15, name='data[5]', definition=definition['items'][5], rule='oneOf'),
     ),
 ])
 def test_integration(asserter, value, expected):