From 656918f08bbbf167e11d9c7ac71d431bf9742676 Mon Sep 17 00:00:00 2001
From: itchyny <itchyny@cybozu.co.jp>
Date: Sun, 25 Feb 2024 21:53:43 +0900
Subject: [PATCH] Implement pick/1 filter

---
 prelude.jq                     |  1 +
 tests/from_manual/functions.rs | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/prelude.jq b/prelude.jq
index 1a5f7c6..78bf095 100644
--- a/prelude.jq
+++ b/prelude.jq
@@ -41,6 +41,7 @@ def nth($n): .[$n];
 
 def del(f): delpaths([path(f)]);
 def setpath($paths; $v): getpath($paths) |= $v;
+def pick(f): . as $v | reduce path(f) as $p (null; setpath($p; $v | getpath($p)));
 
 def to_entries: [keys[] as $key | {$key, value: .[$key]}];
 def from_entries: reduce .[] as $entry ({}; .[$entry.key]=$entry.value);
diff --git a/tests/from_manual/functions.rs b/tests/from_manual/functions.rs
index 7a9eaf2..37a2f19 100644
--- a/tests/from_manual/functions.rs
+++ b/tests/from_manual/functions.rs
@@ -264,6 +264,19 @@ test!(
     "#
 );
 
+test!(
+    pick1,
+    r#"
+    pick(.x, .y[2], .y[0], .z)
+    "#,
+    r#"
+    {"x":1,"y":[1,2,3]}
+    "#,
+    r#"
+    {"x":1,"y":[1,null,3],"z":null}
+    "#
+);
+
 test!(
     entries1,
     r#"