Print offending object in runtime error messages

When reporting an error to the user, add information about the offending
object/value (possibly truncated).

The goal is to give a user some context regarding which input object
caused the runtime error.

Examples:

    $ echo '"hello"' | ./jq '-.'
    jq: error: string ("hello") cannot be negated

    $ echo '"very-long-string"' | ./jq '-.'
    jq: error: string ("very-long-...) cannot be negated

    $ echo '["1",2]' | ./jq '.|join(",")'
    jq: error: string (",") and number (2) cannot be added

    $ echo '["1","2",{"a":{"b":{"c":33}}}]' | ./jq '.|join(",")'
    jq: error: string (",") and object ({"a":{"b":{...) cannot be added

    $ echo '{"a":{"b":{"c":33}}}' | ./jq '.a | @tsv'
    jq: error: object ({"b":{"c":33}}) cannot be tsv-formatted, only array

(Fix #754)

1 files changed, 7 insertions, 2 deletions

diff --git a/builtin.c b/builtin.c
index 8ea8319c..640c6d79 100644
--- a/builtin.c
+++ b/builtin.c
@@ -22,17 +22,22 @@
 
 
 static jv type_error(jv bad, const char* msg) {
-  jv err = jv_invalid_with_msg(jv_string_fmt("%s %s",
+  char errbuf[15];
+  jv err = jv_invalid_with_msg(jv_string_fmt("%s (%s) %s",
                                              jv_kind_name(jv_get_kind(bad)),
+                                             jv_dump_string_trunc(jv_copy(bad), errbuf, sizeof(errbuf)),
                                              msg));
   jv_free(bad);
   return err;
 }
 
 static jv type_error2(jv bad1, jv bad2, const char* msg) {
-  jv err = jv_invalid_with_msg(jv_string_fmt("%s and %s %s",
+  char errbuf1[15],errbuf2[15];
+  jv err = jv_invalid_with_msg(jv_string_fmt("%s (%s) and %s (%s) %s",
                                              jv_kind_name(jv_get_kind(bad1)),
+                                             jv_dump_string_trunc(jv_copy(bad1), errbuf1, sizeof(errbuf1)),
                                              jv_kind_name(jv_get_kind(bad2)),
+                                             jv_dump_string_trunc(jv_copy(bad2), errbuf2, sizeof(errbuf2)),
                                              msg));
   jv_free(bad1);
   jv_free(bad2);