Fix unexpected trailing decimal point (#1153)

include/fmt/format.h

@@ -1187,12 +1187,14 @@ It grisu_prettify(const char* digits, int size, int exp, It it,
   } else if (full_exp > 0) {
     // 1234e-2 -> 12.34[0+]
     it = copy_str<Char>(digits, digits + full_exp, it);
-    *it++ = static_cast<Char>('.');
     if (!params.trailing_zeros) {
       // Remove trailing zeros.
       while (size > full_exp && digits[size - 1] == '0') --size;
+      if (size != full_exp)
+        *it++ = static_cast<Char>('.');
       return copy_str<Char>(digits + full_exp, digits + size, it);
     }
+    *it++ = static_cast<Char>('.');
     it = copy_str<Char>(digits + full_exp, digits + size, it);
     if (params.num_digits > size) {
       // Add trailing zeros.

test/printf-test.cc

@@ -406,6 +406,8 @@ TEST(PrintfTest, Float) {
   EXPECT_PRINTF(buffer, "%E", 392.65);
   EXPECT_PRINTF("392.65", "%g", 392.65);
   EXPECT_PRINTF("392.65", "%G", 392.65);
+  EXPECT_PRINTF("392", "%g", 392.0);
+  EXPECT_PRINTF("392", "%G", 392.0);
   safe_sprintf(buffer, "%a", -392.65);
   EXPECT_EQ(buffer, format("{:a}", -392.65));
   safe_sprintf(buffer, "%A", -392.65);