Interpret precision == -128 as "shortest" double conversion

Also use this for converting doubles with QVariant. We generally want
exact results there, rather than adding rounding errors whenever we
convert.

[ChangeLog][QtCore][QLocale] Added special value for double conversion
precision to get shortest accurate representation.

Change-Id: I905b8a103f39adf31d24b6ce2c8a283cf271b597
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

2 files changed, 61 insertions, 26 deletions

diff --git a/tests/auto/corelib/tools/qlocale/test/test.pro b/tests/auto/corelib/tools/qlocale/test/test.pro
index bb12758107..4777030dd7 100644
--- a/tests/auto/corelib/tools/qlocale/test/test.pro
+++ b/tests/auto/corelib/tools/qlocale/test/test.pro
@@ -4,6 +4,10 @@ QT = core testlib core-private
 embedded: QT += gui
 SOURCES = ../tst_qlocale.cpp
 
+!contains(QT_CONFIG, doubleconversion):!contains(QT_CONFIG, system-doubleconversion) {
+    DEFINES += QT_NO_DOUBLECONVERSION
+}
+
 TARGET = ../tst_qlocale
 win32 {
     CONFIG(debug, debug|release) {
diff --git a/tests/auto/corelib/tools/qlocale/tst_qlocale.cpp b/tests/auto/corelib/tools/qlocale/tst_qlocale.cpp
index 96b91f4fd4..683f7490e5 100644
--- a/tests/auto/corelib/tools/qlocale/tst_qlocale.cpp
+++ b/tests/auto/corelib/tools/qlocale/tst_qlocale.cpp
@@ -772,20 +772,28 @@ void tst_QLocale::doubleToString_data()
     QTest::addColumn<char>("mode");
     QTest::addColumn<int>("precision");
 
-    QTest::newRow("C 3.4 f 5")  << QString("C") << QString("3.40000")     << 3.4 << 'f' << 5;
-    QTest::newRow("C 3.4 f 0")  << QString("C") << QString("3")           << 3.4 << 'f' << 0;
-    QTest::newRow("C 3.4 e 5")  << QString("C") << QString("3.40000e+00") << 3.4 << 'e' << 5;
-    QTest::newRow("C 3.4 e 0")  << QString("C") << QString("3e+00")       << 3.4 << 'e' << 0;
-    QTest::newRow("C 3.4 g 5")  << QString("C") << QString("3.4")         << 3.4 << 'g' << 5;
-    QTest::newRow("C 3.4 g 1")  << QString("C") << QString("3")           << 3.4 << 'g' << 1;
-
-    QTest::newRow("C 3.4 f 1")  << QString("C") << QString("3.4")     << 3.4 << 'f' << 1;
-    QTest::newRow("C 3.4 e 1")  << QString("C") << QString("3.4e+00") << 3.4 << 'e' << 1;
-    QTest::newRow("C 3.4 g 2")  << QString("C") << QString("3.4")     << 3.4 << 'g' << 2;
-
-    QTest::newRow("de_DE 3,4 f 1")  << QString("de_DE") << QString("3,4")     << 3.4 << 'f' << 1;
-    QTest::newRow("de_DE 3,4 e 1")  << QString("de_DE") << QString("3,4e+00") << 3.4 << 'e' << 1;
-    QTest::newRow("de_DE 3,4 g 2")  << QString("de_DE") << QString("3,4")     << 3.4 << 'g' << 2;
+    int shortest = QLocale::FloatingPointShortest;
+
+    QTest::newRow("C 3.4 f 5") << QString("C") << QString("3.40000")     << 3.4 << 'f' << 5;
+    QTest::newRow("C 3.4 f 0") << QString("C") << QString("3")           << 3.4 << 'f' << 0;
+    QTest::newRow("C 3.4 e 5") << QString("C") << QString("3.40000e+00") << 3.4 << 'e' << 5;
+    QTest::newRow("C 3.4 e 0") << QString("C") << QString("3e+00")       << 3.4 << 'e' << 0;
+    QTest::newRow("C 3.4 g 5") << QString("C") << QString("3.4")         << 3.4 << 'g' << 5;
+    QTest::newRow("C 3.4 g 1") << QString("C") << QString("3")           << 3.4 << 'g' << 1;
+
+    QTest::newRow("C 3.4 f 1") << QString("C") << QString("3.4")     << 3.4 << 'f' << 1;
+    QTest::newRow("C 3.4 f -") << QString("C") << QString("3.4")     << 3.4 << 'f' << shortest;
+    QTest::newRow("C 3.4 e 1") << QString("C") << QString("3.4e+00") << 3.4 << 'e' << 1;
+    QTest::newRow("C 3.4 e -") << QString("C") << QString("3.4e+00") << 3.4 << 'e' << shortest;
+    QTest::newRow("C 3.4 g 2") << QString("C") << QString("3.4")     << 3.4 << 'g' << 2;
+    QTest::newRow("C 3.4 g -") << QString("C") << QString("3.4")     << 3.4 << 'g' << shortest;
+
+    QTest::newRow("de_DE 3,4 f 1") << QString("de_DE") << QString("3,4")     << 3.4 << 'f' << 1;
+    QTest::newRow("de_DE 3,4 f -") << QString("de_DE") << QString("3,4")     << 3.4 << 'f' << shortest;
+    QTest::newRow("de_DE 3,4 e 1") << QString("de_DE") << QString("3,4e+00") << 3.4 << 'e' << 1;
+    QTest::newRow("de_DE 3,4 e -") << QString("de_DE") << QString("3,4e+00") << 3.4 << 'e' << shortest;
+    QTest::newRow("de_DE 3,4 g 2") << QString("de_DE") << QString("3,4")     << 3.4 << 'g' << 2;
+    QTest::newRow("de_DE 3,4 g -") << QString("de_DE") << QString("3,4")     << 3.4 << 'g' << shortest;
 
     QTest::newRow("C 0.035003945 f 12") << QString("C") << QString("0.035003945000")   << 0.035003945 << 'f' << 12;
     QTest::newRow("C 0.035003945 f 6")  << QString("C") << QString("0.035004")         << 0.035003945 << 'f' << 6;
@@ -794,13 +802,19 @@ void tst_QLocale::doubleToString_data()
     QTest::newRow("C 0.035003945 g 11") << QString("C") << QString("0.035003945")      << 0.035003945 << 'g' << 11;
     QTest::newRow("C 0.035003945 g 5")  << QString("C") << QString("0.035004")         << 0.035003945 << 'g' << 5;
 
-    QTest::newRow("C 0.035003945 f 9")  << QString("C") << QString("0.035003945")   << 0.035003945 << 'f' << 9;
-    QTest::newRow("C 0.035003945 e 7")  << QString("C") << QString("3.5003945e-02") << 0.035003945 << 'e' << 7;
-    QTest::newRow("C 0.035003945 g 8")  << QString("C") << QString("0.035003945")   << 0.035003945 << 'g' << 8;
+    QTest::newRow("C 0.035003945 f 9") << QString("C") << QString("0.035003945")   << 0.035003945 << 'f' << 9;
+    QTest::newRow("C 0.035003945 f -") << QString("C") << QString("0.035003945")   << 0.035003945 << 'f' << shortest;
+    QTest::newRow("C 0.035003945 e 7") << QString("C") << QString("3.5003945e-02") << 0.035003945 << 'e' << 7;
+    QTest::newRow("C 0.035003945 e -") << QString("C") << QString("3.5003945e-02") << 0.035003945 << 'e' << shortest;
+    QTest::newRow("C 0.035003945 g 8") << QString("C") << QString("0.035003945")   << 0.035003945 << 'g' << 8;
+    QTest::newRow("C 0.035003945 g -") << QString("C") << QString("0.035003945")   << 0.035003945 << 'g' << shortest;
 
-    QTest::newRow("de_DE 0,035003945 f 9")  << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'f' << 9;
-    QTest::newRow("de_DE 0,035003945 e 7")  << QString("de_DE") << QString("3,5003945e-02") << 0.035003945 << 'e' << 7;
-    QTest::newRow("de_DE 0,035003945 g 8")  << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'g' << 8;
+    QTest::newRow("de_DE 0,035003945 f 9") << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'f' << 9;
+    QTest::newRow("de_DE 0,035003945 f -") << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'f' << shortest;
+    QTest::newRow("de_DE 0,035003945 e 7") << QString("de_DE") << QString("3,5003945e-02") << 0.035003945 << 'e' << 7;
+    QTest::newRow("de_DE 0,035003945 e -") << QString("de_DE") << QString("3,5003945e-02") << 0.035003945 << 'e' << shortest;
+    QTest::newRow("de_DE 0,035003945 g 8") << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'g' << 8;
+    QTest::newRow("de_DE 0,035003945 g -") << QString("de_DE") << QString("0,035003945")   << 0.035003945 << 'g' << shortest;
 
     QTest::newRow("C 0.000003945 f 12") << QString("C") << QString("0.000003945000") << 0.000003945 << 'f' << 12;
     QTest::newRow("C 0.000003945 f 6")  << QString("C") << QString("0.000004")       << 0.000003945 << 'f' << 6;
@@ -809,13 +823,19 @@ void tst_QLocale::doubleToString_data()
     QTest::newRow("C 0.000003945 g 7")  << QString("C") << QString("3.945e-06")      << 0.000003945 << 'g' << 7;
     QTest::newRow("C 0.000003945 g 1")  << QString("C") << QString("4e-06")          << 0.000003945 << 'g' << 1;
 
-    QTest::newRow("C 0.000003945 f 9")  << QString("C") << QString("0.000003945") << 0.000003945 << 'f' << 9;
-    QTest::newRow("C 0.000003945 e 3")  << QString("C") << QString("3.945e-06")   << 0.000003945 << 'e' << 3;
-    QTest::newRow("C 0.000003945 g 4")  << QString("C") << QString("3.945e-06")   << 0.000003945 << 'g' << 4;
+    QTest::newRow("C 0.000003945 f 9") << QString("C") << QString("0.000003945") << 0.000003945 << 'f' << 9;
+    QTest::newRow("C 0.000003945 f -") << QString("C") << QString("0.000003945") << 0.000003945 << 'f' << shortest;
+    QTest::newRow("C 0.000003945 e 3") << QString("C") << QString("3.945e-06")   << 0.000003945 << 'e' << 3;
+    QTest::newRow("C 0.000003945 e -") << QString("C") << QString("3.945e-06")   << 0.000003945 << 'e' << shortest;
+    QTest::newRow("C 0.000003945 g 4") << QString("C") << QString("3.945e-06")   << 0.000003945 << 'g' << 4;
+    QTest::newRow("C 0.000003945 g -") << QString("C") << QString("3.945e-06")   << 0.000003945 << 'g' << shortest;
 
-    QTest::newRow("de_DE 0,000003945 f 9")  << QString("de_DE") << QString("0,000003945") << 0.000003945 << 'f' << 9;
-    QTest::newRow("de_DE 0,000003945 e 3")  << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'e' << 3;
-    QTest::newRow("de_DE 0,000003945 g 4")  << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'g' << 4;
+    QTest::newRow("de_DE 0,000003945 f 9") << QString("de_DE") << QString("0,000003945") << 0.000003945 << 'f' << 9;
+    QTest::newRow("de_DE 0,000003945 f -") << QString("de_DE") << QString("0,000003945") << 0.000003945 << 'f' << shortest;
+    QTest::newRow("de_DE 0,000003945 e 3") << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'e' << 3;
+    QTest::newRow("de_DE 0,000003945 e -") << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'e' << shortest;
+    QTest::newRow("de_DE 0,000003945 g 4") << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'g' << 4;
+    QTest::newRow("de_DE 0,000003945 g -") << QString("de_DE") << QString("3,945e-06")   << 0.000003945 << 'g' << shortest;
 
     QTest::newRow("C 12456789012 f 3")  << QString("C") << QString("12456789012.000")     << 12456789012.0 << 'f' << 3;
     QTest::newRow("C 12456789012 e 13") << QString("C") << QString("1.2456789012000e+10") << 12456789012.0 << 'e' << 13;
@@ -824,12 +844,18 @@ void tst_QLocale::doubleToString_data()
     QTest::newRow("C 12456789012 g 8")  << QString("C") << QString("1.2456789e+10")       << 12456789012.0 << 'g' << 8;
 
     QTest::newRow("C 12456789012 f 0")  << QString("C") << QString("12456789012")      << 12456789012.0 << 'f' << 0;
+    QTest::newRow("C 12456789012 f -")  << QString("C") << QString("12456789012")      << 12456789012.0 << 'f' << shortest;
     QTest::newRow("C 12456789012 e 10") << QString("C") << QString("1.2456789012e+10") << 12456789012.0 << 'e' << 10;
+    QTest::newRow("C 12456789012 e -")  << QString("C") << QString("1.2456789012e+10") << 12456789012.0 << 'e' << shortest;
     QTest::newRow("C 12456789012 g 11") << QString("C") << QString("12456789012")      << 12456789012.0 << 'g' << 11;
+    QTest::newRow("C 12456789012 g -")  << QString("C") << QString("12456789012")      << 12456789012.0 << 'g' << shortest;
 
     QTest::newRow("de_DE 12456789012 f 0")  << QString("de_DE") << QString("12.456.789.012")   << 12456789012.0 << 'f' << 0;
+    QTest::newRow("de_DE 12456789012 f -")  << QString("de_DE") << QString("12.456.789.012")   << 12456789012.0 << 'f' << shortest;
     QTest::newRow("de_DE 12456789012 e 10") << QString("de_DE") << QString("1,2456789012e+10") << 12456789012.0 << 'e' << 10;
+    QTest::newRow("de_DE 12456789012 e -")  << QString("de_DE") << QString("1,2456789012e+10") << 12456789012.0 << 'e' << shortest;
     QTest::newRow("de_DE 12456789012 g 11") << QString("de_DE") << QString("12.456.789.012")   << 12456789012.0 << 'g' << 11;
+    QTest::newRow("de_DE 12456789012 g -")  << QString("de_DE") << QString("12.456.789.012")   << 12456789012.0 << 'g' << shortest;
 }
 
 void tst_QLocale::doubleToString()
@@ -840,6 +866,11 @@ void tst_QLocale::doubleToString()
     QFETCH(char, mode);
     QFETCH(int, precision);
 
+#ifdef QT_NO_DOUBLECONVERSION
+    if (precision == QLocale::FloatingPointShortest)
+        QSKIP("'Shortest' double conversion is not that short without libdouble-conversion");
+#endif
+
     const QLocale locale(locale_name);
     QCOMPARE(locale.toString(num, mode, precision), num_str);