From 69779b4ed6e78dfc5a87ee2fead6da3dcbf04134 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Tue, 24 Mar 2020 09:01:57 -0700
Subject: [PATCH] Fix handling of small precision in general format

---
 include/fmt/format.h | 6 ++++--
 test/format-test.cc  | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index bb9bc1e5..dc2531e8 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1152,9 +1152,11 @@ template <typename Char> class float_writer {
       // 1234e-6 -> 0.001234
       *it++ = static_cast<Char>('0');
       int num_zeros = -full_exp;
-      if (specs_.precision >= 0 && specs_.precision < num_zeros)
-        num_zeros = specs_.precision;
       int num_digits = num_digits_;
+      if (num_digits == 0 && specs_.precision >= 0 &&
+          specs_.precision < num_zeros) {
+        num_zeros = specs_.precision;
+      }
       // Remove trailing zeros.
       if (!specs_.showpoint)
         while (num_digits > 0 && digits_[num_digits - 1] == '0') --num_digits;
diff --git a/test/format-test.cc b/test/format-test.cc
index a2223749..4e553022 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1125,6 +1125,7 @@ TEST(FormatterTest, Precision) {
       format("{:.838A}", -2.14001164E+38));
   EXPECT_EQ("123.", format("{:#.0f}", 123.0));
   EXPECT_EQ("1.23", format("{:.02f}", 1.234));
+  EXPECT_EQ("0.001", format("{:.1g}", 0.001));
 
   EXPECT_THROW_MSG(format("{0:.2}", reinterpret_cast<void*>(0xcafe)),
                    format_error,