Add sloppy_existing_atom as a configuration option for labels

README.md

@@ -467,18 +467,20 @@ decode(JSON, Opts) -> Term
   JSON = json_text()
   Term = json_term()
   Opts = [option() | labels | {labels, Label} | {post_decode, F}]
-    Label = binary | atom | existing_atom
+    Label = binary | atom | existing_atom | sloppy_existing_atom
     F = fun((any()) -> any())
 ```
 
 `decode` parses a json text (a `utf8` encoded binary) and produces an erlang 
 term
 
-the option `labels` controls how keys are converted from json to erlang terms. 
+the option `labels` controls how keys are converted from json to
-`binary` does no conversion beyond normal escaping. `atom` converts keys to 
+erlang terms.  `binary` (the default behavior) does no conversion
-erlang atoms and results in a badarg error if the keys fall outside the range of 
+beyond normal escaping. `atom` converts keys to erlang atoms and
-erlang atoms. `existing_atom` is identical to `atom` except it will not add new 
+results in a badarg error if the keys fall outside the range of erlang
-atoms to the atom table
+atoms. `existing_atom` is identical to `atom` except it will not add
+new atoms to the atom table. `sloppy_existing_atom` will convert keys
+to atoms when they exist, and leave them as binary otherwise
 
 `{post_decode, F}` is a user defined function of arity 1 that is called on each 
 output value (objects, arrays, strings, numbers and literals). it may return any 

src/jsx_to_term.erl

@@ -53,7 +53,7 @@ to_term(Source, Config) when is_list(Config) ->
 parse_config(Config) -> parse_config(Config, #config{}).
 
 parse_config([{labels, Val}|Rest], Config)
-        when Val == binary; Val == atom; Val == existing_atom ->
+        when Val == binary; Val == atom; Val == existing_atom; Val == sloppy_existing_atom ->
     parse_config(Rest, Config#config{labels = Val});
 parse_config([labels|Rest], Config) ->
     parse_config(Rest, Config#config{labels = binary});
@@ -107,6 +107,12 @@ format_key(Key, Config) ->
         binary -> Key
         ; atom -> binary_to_atom(Key, utf8)
         ; existing_atom -> binary_to_existing_atom(Key, utf8)
+        ; sloppy_existing_atom ->
+            try binary_to_existing_atom(Key, utf8) of
+                Result -> Result
+            catch
+                error:badarg -> Key
+            end
     end.
 
 
@@ -133,6 +139,10 @@ config_test_() ->
             #config{labels=existing_atom},
             parse_config([{labels, existing_atom}])
         )},
+        {"sloppy existing atom labels", ?_assertEqual(
+            #config{labels=sloppy_existing_atom},
+            parse_config([{labels, sloppy_existing_atom}])
+        )},
         {"post decode", ?_assertEqual(
             #config{post_decode=F},
             parse_config([{post_decode, F}])
@@ -154,6 +164,14 @@ format_key_test_() ->
         {"nonexisting atom key", ?_assertError(
             badarg,
             format_key(<<"nonexistentatom">>, #config{labels=existing_atom})
+        )},
+        {"sloppy existing atom key", ?_assertEqual(
+            key,
+            format_key(<<"key">>, #config{labels=sloppy_existing_atom})
+        )},
+        {"nonexisting atom key", ?_assertEqual(
+            <<"nonexistentatom">>,
+            format_key(<<"nonexistentatom">>, #config{labels=sloppy_existing_atom})
         )}
     ].