From 387098fc87c5301aeba3f64749322de9bbef1b0d Mon Sep 17 00:00:00 2001
From: Luccas Mateus <Luccasmmg@gmail.com>
Date: Wed, 31 Mar 2021 03:01:39 -0300
Subject: [PATCH] Stop nu panicks in math.round on a large decimal value(Most
 of the time) (#3224)

* Stop crashing when dealing with large numbers in math round

* Fix formatting

* add tests

* just to trigger wasm build

* trigger wasm build
---
 crates/nu-command/src/commands/math/round.rs  |  7 +++++--
 crates/nu-command/tests/commands/math/mod.rs  |  1 +
 .../nu-command/tests/commands/math/round.rs   | 21 +++++++++++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 crates/nu-command/tests/commands/math/round.rs

diff --git a/crates/nu-command/src/commands/math/round.rs b/crates/nu-command/src/commands/math/round.rs
index 33000fcbe8..0c36888d8c 100644
--- a/crates/nu-command/src/commands/math/round.rs
+++ b/crates/nu-command/src/commands/math/round.rs
@@ -76,9 +76,12 @@ fn round_big_int(val: BigInt) -> Value {
 
 fn round_big_decimal(val: BigDecimal, precision: i64) -> Value {
     if precision > 0 {
-        UntaggedValue::decimal(val.round(precision)).into()
+        UntaggedValue::decimal(val.with_scale(precision + 1).round(precision)).into()
     } else {
-        let (rounded, _) = val.round(precision).as_bigint_and_exponent();
+        let (rounded, _) = val
+            .with_scale(precision + 1)
+            .round(precision)
+            .as_bigint_and_exponent();
         UntaggedValue::int(rounded).into()
     }
 }
diff --git a/crates/nu-command/tests/commands/math/mod.rs b/crates/nu-command/tests/commands/math/mod.rs
index d95769174a..3bbcc3ea17 100644
--- a/crates/nu-command/tests/commands/math/mod.rs
+++ b/crates/nu-command/tests/commands/math/mod.rs
@@ -1,6 +1,7 @@
 mod avg;
 mod eval;
 mod median;
+mod round;
 mod sum;
 
 use nu_test_support::{nu, pipeline};
diff --git a/crates/nu-command/tests/commands/math/round.rs b/crates/nu-command/tests/commands/math/round.rs
new file mode 100644
index 0000000000..2bec436a64
--- /dev/null
+++ b/crates/nu-command/tests/commands/math/round.rs
@@ -0,0 +1,21 @@
+use nu_test_support::nu;
+
+#[test]
+fn can_round_very_large_numbers() {
+    let actual = nu!(
+        cwd: ".",
+        "echo 18.1372544780074142289927665486772012345 | math round"
+    );
+
+    assert_eq!(actual.out, "18")
+}
+
+#[test]
+fn can_round_very_large_numbers_with_precision() {
+    let actual = nu!(
+        cwd: ".",
+        "echo 18.13725447800741422899276654867720121457878988 | math round -p 10"
+    );
+
+    assert_eq!(actual.out, "18.137254478")
+}