From 488f15207b629919056781b5646d08e46e658684 Mon Sep 17 00:00:00 2001
From: Deep Goel <deepgoel@google.com>
Date: Fri, 5 May 2023 14:02:34 +0530
Subject: [PATCH] Add std.maxArray in standard library

---
 doc/_stdlib_gen/stdlib-content.jsonnet |  8 ++++++++
 stdlib/std.jsonnet                     | 12 ++++++++++++
 test_suite/stdlib.jsonnet              |  9 +++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/doc/_stdlib_gen/stdlib-content.jsonnet b/doc/_stdlib_gen/stdlib-content.jsonnet
index 40de10df5..39231f848 100644
--- a/doc/_stdlib_gen/stdlib-content.jsonnet
+++ b/doc/_stdlib_gen/stdlib-content.jsonnet
@@ -1429,6 +1429,14 @@ local html = import 'html.libsonnet';
             |||
               Return the min of all element in <code>arr</code>.
         },
+        {
+          name: 'maxArray',
+          params: ['arr', 'keyF', 'onEmpty'],
+          availableSince: 'upcoming',
+          description: html.paragraphs([
+            |||
+              Return the max of all element in <code>arr</code>.
+        },
         {
           name: 'contains',
           params: ['arr', 'elem'],
diff --git a/stdlib/std.jsonnet b/stdlib/std.jsonnet
index 160dd7eb3..479c84371 100644
--- a/stdlib/std.jsonnet
+++ b/stdlib/std.jsonnet
@@ -1715,6 +1715,18 @@ limitations under the License.
           a;
       std.foldl(minFn, arr, minVal),
 
+  maxArray(arr, keyF=id, onEmpty=error 'Expected at least one element in array. Got none')::
+    if std.length(arr) == 0 then
+      onEmpty
+    else
+      local maxVal = arr[0];
+      local maxFn(a, b) =
+        if std.__compare(keyF(a), keyF(b)) < 0 then
+          b
+        else
+          a;
+      std.foldl(maxFn, arr, maxVal),
+
   xor(x, y):: x != y,
 
   xnor(x, y):: x == y,
diff --git a/test_suite/stdlib.jsonnet b/test_suite/stdlib.jsonnet
index 186399245..28cad43ce 100644
--- a/test_suite/stdlib.jsonnet
+++ b/test_suite/stdlib.jsonnet
@@ -1547,6 +1547,11 @@ std.assertEqual(std.sum([1, 2, 3]), 6) &&
 std.assertEqual(std.minArray([1, 2, 3]), 1) &&
 std.assertEqual(std.minArray(['1', '2', '3']), '1') &&
 
+std.assertEqual(std.maxArray([1, 2, 3]), 3) &&
+std.assertEqual(std.maxArray(['1', '2', '3']), '3') &&
+std.assertEqual(std.maxArray(['a', 'x', 'z']), 'z') &&
+
+
 std.assertEqual(std.xor(true, false), true) &&
 std.assertEqual(std.xor(true, true), false) &&
 
@@ -1559,7 +1564,7 @@ std.assertEqual(std.round(1.5), 2) &&
 std.assertEqual(std.isEmpty(''), true) &&
 std.assertEqual(std.isEmpty('non-empty string'), false) &&
 
-std.contains(std.contains([1, 2, 3], 2), true) &&
-std.contains(std.contains([1, 2, 3], "foo"), false) &&
+std.assertEqual(std.contains([1, 2, 3], 2), true) &&
+std.assertEqual(std.contains([1, 2, 3], 'foo'), false) &&
 
 true