From ff486a72a764ff9f0ea3be460bd713ed7a237db6 Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Sat, 14 Mar 2020 11:37:38 -0700
Subject: [PATCH] Allow leading zeros in precision (#1579)

---
 include/fmt/format.h | 10 +++++-----
 test/format-test.cc  |  1 +
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index ee7f0f93..a529383a 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1953,10 +1953,6 @@ template <typename Char, typename ErrorHandler>
 FMT_CONSTEXPR int parse_nonnegative_int(const Char*& begin, const Char* end,
                                         ErrorHandler&& eh) {
   FMT_ASSERT(begin != end && '0' <= *begin && *begin <= '9', "");
-  if (*begin == '0') {
-    ++begin;
-    return 0;
-  }
   unsigned value = 0;
   // Convert to unsigned to prevent a warning.
   constexpr unsigned max_int = max_value<int>();
@@ -2311,7 +2307,11 @@ FMT_CONSTEXPR const Char* parse_arg_id(const Char* begin, const Char* end,
     return begin;
   }
   if (c >= '0' && c <= '9') {
-    int index = parse_nonnegative_int(begin, end, handler);
+    int index = 0;
+    if (c != '0')
+      index = parse_nonnegative_int(begin, end, handler);
+    else
+      ++begin;
     if (begin == end || (*begin != '}' && *begin != ':'))
       handler.on_error("invalid format string");
     else
diff --git a/test/format-test.cc b/test/format-test.cc
index af72acaf..a2223749 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1124,6 +1124,7 @@ TEST(FormatterTest, Precision) {
       "000000000000000000000000000000000000000000000000000P+127",
       format("{:.838A}", -2.14001164E+38));
   EXPECT_EQ("123.", format("{:#.0f}", 123.0));
+  EXPECT_EQ("1.23", format("{:.02f}", 1.234));
 
   EXPECT_THROW_MSG(format("{0:.2}", reinterpret_cast<void*>(0xcafe)),
                    format_error,