From 5e53a690ace8dce64f72a5a734def8e832f6b7d3 Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Sat, 19 Jun 2021 17:00:31 +0300
Subject: [PATCH] AK: Add support for keeping trailing zeros in fixed precision
 floats

This uses the same syntax as zero padding integers:
String::formatted("{:0.5}", 1.234) => "1.23400"
---
 AK/Format.cpp           | 11 ++++++++---
 AK/Format.h             |  1 +
 Tests/AK/TestFormat.cpp |  6 ++++++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/AK/Format.cpp b/AK/Format.cpp
index 82047a8673..5385d5552f 100644
--- a/AK/Format.cpp
+++ b/AK/Format.cpp
@@ -334,6 +334,7 @@ void FormatBuilder::put_f64(
     double value,
     u8 base,
     bool upper_case,
+    bool zero_pad,
     Align align,
     size_t min_width,
     size_t precision,
@@ -367,10 +368,14 @@ void FormatBuilder::put_f64(
             epsilon *= 10.0;
         }
 
-        if (visible_precision > 0) {
+        if (zero_pad || visible_precision > 0)
             string_builder.append('.');
+
+        if (visible_precision > 0)
             format_builder.put_u64(static_cast<u64>(value), base, false, upper_case, true, Align::Right, visible_precision);
-        }
+
+        if (zero_pad && (precision - visible_precision) > 0)
+            format_builder.put_u64(0, base, false, false, true, Align::Right, precision - visible_precision);
     }
 
     put_string(string_builder.string_view(), align, min_width, NumericLimits<size_t>::max(), fill);
@@ -623,7 +628,7 @@ void Formatter<double>::format(FormatBuilder& builder, double value)
     m_width = m_width.value_or(0);
     m_precision = m_precision.value_or(6);
 
-    builder.put_f64(value, base, upper_case, m_align, m_width.value(), m_precision.value(), m_fill, m_sign_mode);
+    builder.put_f64(value, base, upper_case, m_zero_pad, m_align, m_width.value(), m_precision.value(), m_fill, m_sign_mode);
 }
 void Formatter<float>::format(FormatBuilder& builder, float value)
 {
diff --git a/AK/Format.h b/AK/Format.h
index cae81e821a..3eb562752d 100644
--- a/AK/Format.h
+++ b/AK/Format.h
@@ -189,6 +189,7 @@ public:
         double value,
         u8 base = 10,
         bool upper_case = false,
+        bool zero_pad = false,
         Align align = Align::Right,
         size_t min_width = 0,
         size_t precision = 6,
diff --git a/Tests/AK/TestFormat.cpp b/Tests/AK/TestFormat.cpp
index 9e0aad7810..50ddde2f47 100644
--- a/Tests/AK/TestFormat.cpp
+++ b/Tests/AK/TestFormat.cpp
@@ -252,6 +252,12 @@ TEST_CASE(yay_this_implementation_sucks)
     EXPECT_EQ(String::formatted("{:.0}", .99999999999), "0");
 }
 
+TEST_CASE(precision_with_trailing_zeros)
+{
+    EXPECT_EQ(String::formatted("{:0.3}", 1.12), "1.120");
+    EXPECT_EQ(String::formatted("{:0.1}", 1.12), "1.1");
+}
+
 TEST_CASE(magnitude_less_than_zero)
 {
     EXPECT_EQ(String::formatted("{}", -0.654), "-0.654");