From 6d1e5fb1df5e1057c3c9d9d1d65ecb88c1254d3e Mon Sep 17 00:00:00 2001
From: pkoppstein <pkoppstein@gmail.com>
Date: Thu, 27 Jul 2023 18:08:33 -0400
Subject: [PATCH] execute.c: support pick(last)

Support [0] | setpath([-1]; _)
Add tests for pick/1
---
 src/execute.c |  8 ++++++++
 tests/jq.test | 23 +++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/execute.c b/src/execute.c
index 091ddbc355..198ad26663 100644
--- a/src/execute.c
+++ b/src/execute.c
@@ -687,6 +687,14 @@ jv jq_next(jq_state *jq) {
         set_error(jq, jv_invalid_with_msg(msg));
         goto do_backtrack;
       }
+      // $array | .[-1]
+      if (jv_get_kind(k) == JV_KIND_NUMBER && jv_get_kind(t) == JV_KIND_ARRAY) {
+        int idx = jv_number_value(k);
+        if (idx < 0) {
+          jv_free(k);
+          k = jv_number(jv_array_length(jv_copy(t)) + idx);
+        }
+      }
       jv v = jv_get(t, jv_copy(k));
       if (jv_is_valid(v)) {
         path_append(jq, k, jv_copy(v));
diff --git a/tests/jq.test b/tests/jq.test
index f3804a7da2..177c4afd06 100644
--- a/tests/jq.test
+++ b/tests/jq.test
@@ -1002,6 +1002,28 @@ del(.[1], .[-6], .[2], .[-3:9])
 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 [0, 3, 5, 6, 9]
 
+# negative index
+setpath([-1]; 1)
+[0]
+[1]
+
+pick(.a.b.c)
+null
+{"a":{"b":{"c":null}}}
+
+pick(first)
+[1,2]
+[1]
+
+pick(first|first)
+[[10,20],30]
+[[10]]
+
+# negative indices in path expressions (since last/1 is .[-1])
+pick(last)
+[[10,20],30]
+[null,30]
+
 #
 # Assignment
 #
@@ -1873,6 +1895,7 @@ try input catch .
 null
 "break"
 
+# debug should emit its input
 debug
 1
 1