Don't 500 if search attribute is invalid

In the case where a user, when providing a search, provides an attribute
constraint (-a flag) that is invalid, we currently throw a 500. An
invalid attribute constraint most commonly is specifying a nested hash
using dot-notation when one or more values in that constraint are, in
fact, not a hash. This change prevents the system from throwing a 500
and presents the user with a more correct result, that there is no value
for that attribute (because it doesn't exist).

For example, `knife search node "*:*" -a uptime.seconds` is invalid
because the key `'uptime'` does exist but it is a string, not a
hash. Thus, ej attempts to fetch the key `'seconds'` from that string,
throwing an error within ej for an invalid function clause. With this
change, the search will return just fine but show that there is no value
for `uptime.seconds`.

Signed-off-by: Tom Duffield <[email protected]>

src/oc_erchef/apps/oc_chef_wm/src/chef_wm_search.erl

@@ -360,7 +360,16 @@ make_query_from_params(Req) ->
 extract_path(_Item, []) ->
     null;
 extract_path(Item, Path) ->
-    ej:get(list_to_tuple(Path), Item, null).
+    try ej:get(list_to_tuple(Path), Item, null) of
+        Result -> Result
+    catch
+        %% Don't throw a 500 when the user input is invalid
+        %%   This typically happens when the user provides an invalid attribute
+        %%   key, typically trying to access a value as a hash that is actually
+        %%   a string (i.e. uptime.seconds)
+        error:function_clause -> null;
+        Error:Reason -> {Error, Reason}
+    end.
 
 make_search_results(BulkGetFun, Ids, BatchSize, Start, NumFound) ->
     Ans0 = search_result_start(Start, NumFound),