[flang][runtime] Don't emit any leading blanks for G0/E0 output editing

[klausler]

Summary

There were cases where E0.d output editing (or G0.d editing that is converted
to E0.d) would emit one or more leading blank characters; fix them.

flang/runtime/edit-output.cpp

   if (edit.modes.editingFlags & signPlus) {
     flags |= decimal::AlwaysSign;
   }
+  bool noLeadingSpaces{editWidth == 0};
   if (editWidth == 0) { // "the processor selects the field width"
     if (edit.digits.has_value()) { // E0.d
       if (editDigits == 0) { // E0.0

       zeroesBeforePoint = 1;
       ++totalLength;
     }
+    if (totalLength < width && noLeadingSpaces) {
+      width = totalLength;
+    }
     return EmitPrefix(edit, totalLength, width) &&
         io_.Emit(converted.str, signLength + digitsBeforePoint) &&
         io_.EmitRepeated('0', zeroesBeforePoint) &&

 template <int binaryPrecision>
 DataEdit RealOutputEditing<binaryPrecision>::EditForGOutput(DataEdit edit) {
   edit.descriptor = 'E';
+  int editWidth{edit.width.value_or(0)};
   int significantDigits{
       edit.digits.value_or(BinaryFloatingPoint::decimalPrecision)}; // 'd'
-  if (!edit.width.has_value() || (*edit.width > 0 && significantDigits == 0)) {
+  if (editWidth > 0 && significantDigits == 0) {
     return edit; // Gw.0 -> Ew.0 for w > 0
   }
   int flags{0};

   decimal::ConversionToDecimalResult converted{
       Convert(significantDigits, edit.modes.round, flags)};
   if (IsInfOrNaN(converted)) {
-    return edit;
+    return edit; // Inf/Nan -> Ew.d (same as Fw.d)
   }
   int expo{IsZero() ? 1 : converted.decimalExponent}; // 's'
   if (expo < 0 || expo > significantDigits) {

   edit.descriptor = 'F';
   edit.modes.scale = 0; // kP is ignored for G when no exponent field
   trailingBlanks_ = 0;
-  int editWidth{edit.width.value_or(0)};
   if (editWidth > 0) {
     int expoDigits{edit.expoDigits.value_or(0)};
     trailingBlanks_ = expoDigits > 0 ? expoDigits + 2 : 4; // 'n'

flang/unittests/Runtime/NumericalFormatTest.cpp

   for (auto const &[format, expect] : zeroes) {
     std::string got;
     ASSERT_TRUE(CompareFormatReal(format, 0.0, expect, got))
-        << "Failed to format " << format << ", expected " << expect << ", got "
-        << got;
+        << "Failed to format " << format << ", expected '" << expect
+        << "', got '" << got << "'";
   }
 }
 

   for (auto const &[format, expect] : ones) {
     std::string got;
     ASSERT_TRUE(CompareFormatReal(format, 1.0, expect, got))
-        << "Failed to format " << format << ", expected " << expect << ", got "
-        << got;
+        << "Failed to format " << format << ", expected '" << expect
+        << "', got '" << got << "'";
   }
 }
 

   for (auto const &[format, expect] : negOnes) {
     std::string got;
     ASSERT_TRUE(CompareFormatReal(format, -1.0, expect, got))
-        << "Failed to format " << format << ", expected " << expect << ", got "
-        << got;
+        << "Failed to format " << format << ", expected '" << expect
+        << "', got '" << got << "'";
   }
 }
 

               {"(E62.55,';')",
                   " 0.1000000000000000055511151231257827021181583404541015625E+"
                   "00;"},
-              {"(E0.0,';')", " 0.E+00;"},
+              {"(E0.0,';')", "0.E+00;"},
               {"(E0.55,';')",
                   "0.1000000000000000055511151231257827021181583404541015625E+"
                   "00;"},

     for (auto const &[format, expect] : cases) {
       std::string got;
       ASSERT_TRUE(CompareFormatReal(format, value, expect, got))
-          << "Failed to format " << format << ", expected " << expect
-          << ", got " << got;
+          << "Failed to format " << format << ", expected '" << expect
+          << "', got '" << got << "'";
     }
   }
 

   for (auto const &[format, value, expect] : individualTestCases) {
     std::string got;
     ASSERT_TRUE(CompareFormatReal(format, value, expect, got))
-        << "Failed to format " << format << ", expected " << expect << ", got "
-        << got;
+        << "Failed to format " << format << ", expected '" << expect
+        << "', got '" << got << "'";
   }
 
   // Problematic EN formatting edge cases with rounding

   for (auto const &[value, expect] : individualENTestCases) {
     std::string got;
     ASSERT_TRUE(CompareFormatReal("(EN10.1)", value, expect, got))
-        << "Failed to format EN10.1, expected " << expect << ", got " << got;
+        << "Failed to format EN10.1, expected '" << expect << "', got '" << got
+        << "'";
   }
 }