String Views: add slice() methods

Methods with preconditions can't be noexcept (from Marc in code
review).

[ChangeLog][QtCore][String Views] Added slice() methods to
Q{String,ByteArray,Latin1String,Utf8String,AnyString}View which work
like sliced() but modify the view they are called on.

Found in API review.

Task-number: QTBUG-99218
Change-Id: Ic8ef3085f7cfac86b8404fb28d491ca38ad121eb
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
(cherry picked from commit 8f68bd9e6353a42d3b71d893b27fec6bedced501)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/text/qanystringview.cpp

@@ -383,7 +383,7 @@ QT_BEGIN_NAMESPACE
     \a n is negative (default), the function returns all code points that
     are available from \a pos.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -398,7 +398,7 @@ QT_BEGIN_NAMESPACE
     The entire string view is returned if \a n is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -413,7 +413,7 @@ QT_BEGIN_NAMESPACE
     The entire string view is returned if \a n is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -425,7 +425,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa last(), sliced(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa last(), sliced(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -436,7 +436,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa first(), sliced(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), sliced(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -451,7 +451,7 @@ QT_BEGIN_NAMESPACE
     or \a pos + \a n > size().
 //! [UB-sliced-index-length]
 
-    \sa first(), last(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), last(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -465,7 +465,32 @@ QT_BEGIN_NAMESPACE
     \note The behavior is undefined when \a pos < 0 or \a pos > size().
 //! [UB-sliced-index-only]
 
-    \sa first(), last(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa first(), last(), chopped(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
+*/
+
+/*!
+    \fn QAnyStringView &QAnyStringView::slice(qsizetype pos, qsizetype n)
+    \since 6.8
+
+    Modifies this string view to start at position \a pos, extending for
+    \a n code points.
+
+    \include qanystringview.cpp UB-sliced-index-length
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
+*/
+
+/*!
+    \fn QAnyStringView &QAnyStringView::slice(qsizetype pos)
+    \since 6.8
+    \overload
+
+    Modifies this string view to start at position \a pos, extending to
+    its end.
+
+    \include qanystringview.cpp UB-sliced-index-only
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -479,7 +504,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa sliced(), first(), last(), chop(), truncate(), {Sizes and Sub-Strings}
+    \sa sliced(), first(), last(), chop(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*!
@@ -505,7 +530,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa sliced(), first(), last(), chopped(), truncate(), {Sizes and Sub-Strings}
+    \sa sliced(), first(), last(), chopped(), truncate(), slice(), {Sizes and Sub-Strings}
 */
 
 /*! \fn template <typename Visitor> decltype(auto) QAnyStringView::visit(Visitor &&v) const

src/corelib/text/qanystringview.h

@@ -259,6 +259,11 @@ public:
     [[nodiscard]] constexpr QAnyStringView chopped(qsizetype n) const
     { verify(0, n); return sliced(0, size() - n); }
 
+    constexpr QAnyStringView &slice(qsizetype pos)
+    { *this = sliced(pos); return *this; }
+    constexpr QAnyStringView &slice(qsizetype pos, qsizetype n)
+    { *this = sliced(pos, n); return *this; }
+
     constexpr void truncate(qsizetype n)
     { verify(0, n); setSize(n); }
     constexpr void chop(qsizetype n)

src/corelib/text/qbytearrayview.h

@@ -205,6 +205,12 @@ public:
     { verify(pos, 0); return QByteArrayView(data() + pos, size() - pos); }
     [[nodiscard]] constexpr QByteArrayView sliced(qsizetype pos, qsizetype n) const
     { verify(pos, n); return QByteArrayView(data() + pos, n); }
+
+     constexpr QByteArrayView &slice(qsizetype pos)
+    { *this = sliced(pos); return *this; }
+     constexpr QByteArrayView &slice(qsizetype pos, qsizetype n)
+    { *this = sliced(pos, n); return *this; }
+
     [[nodiscard]] constexpr QByteArrayView chopped(qsizetype len) const
     { verify(0, len); return sliced(0, size() - len); }
 

src/corelib/text/qbytearrayview.qdoc

@@ -551,7 +551,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa last(), startsWith(), chopped(), chop(), truncate()
+    \sa last(), startsWith(), chopped(), chop(), truncate(), sliced(), slice()
 */
 
 /*!
@@ -562,7 +562,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa first(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), endsWith(), chopped(), chop(), truncate(), sliced(), slice()
 */
 
 /*!
@@ -576,7 +576,7 @@
     or \a pos + \a n > size().
 //! [UB-sliced-index-length]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -589,7 +589,32 @@
     \note The behavior is undefined when \a pos < 0 or \a pos > size().
 //! [UB-sliced-index-only]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
+*/
+
+/*!
+    \fn QByteArrayView &QByteArrayView::slice(qsizetype pos, qsizetype n)
+    \since 6.8
+
+    Modifies this byte array view to start at position \a pos, extending for
+    \a n bytes.
+
+    \include qbytearrayview.qdoc UB-sliced-index-length
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
+*/
+
+/*!
+    \fn QByteArrayView &QByteArrayView::slice(qsizetype pos)
+    \since 6.8
+    \overload
+
+    Modifies this byte array view to start at position \a pos, extending
+    to its end.
+
+    \include qbytearrayview.qdoc UB-sliced-index-only
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
 */
 
 /*!
@@ -603,7 +628,7 @@
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa first(), last(), sliced(), chop(), truncate()
+    \sa first(), last(), sliced(), chop(), truncate(), slice()
 */
 
 /*!
@@ -627,7 +652,7 @@
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa sliced(), first(), last(), chopped(), truncate()
+    \sa sliced(), first(), last(), chopped(), truncate(), slice()
 */
 
 /*!
@@ -645,7 +670,7 @@
     \a length is negative (default), the function returns all characters that
     are available from \a start.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -660,7 +685,7 @@
     The entire byte array view is returned if \a length is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -675,7 +700,7 @@
     The entire byte array view is returned if \a length is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!

src/corelib/text/qlatin1stringview.h

@@ -236,6 +236,11 @@ public:
     [[nodiscard]] constexpr QLatin1StringView chopped(qsizetype n) const
     { verify(0, n); return sliced(0, size() - n); }
 
+    constexpr QLatin1StringView &slice(qsizetype pos)
+    { *this = sliced(pos); return *this; }
+    constexpr QLatin1StringView &slice(qsizetype pos, qsizetype n)
+    { *this = sliced(pos, n); return *this; }
+
     constexpr void chop(qsizetype n)
     { verify(0, n); m_size -= n; }
     constexpr void truncate(qsizetype n)

src/corelib/text/qlatin1stringview.qdoc

@@ -708,7 +708,7 @@
     (default), the function returns all characters that are available from
     \a start.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -724,7 +724,7 @@
     The entire Latin-1 string view is returned if \a length is greater
     than or equal to size(), or less than zero.
 
-    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -740,7 +740,7 @@
     The entire Latin-1 string view is returned if \a length is greater
     than or equal to size(), or less than zero.
 
-    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -752,7 +752,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa last(), startsWith(), chopped(), chop(), truncate()
+    \sa last(), startsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -764,7 +764,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa first(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), endsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -779,7 +779,7 @@
     or \c{pos + n > size()}.
 //! [UB-sliced-index-length]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -793,7 +793,32 @@
     \note The behavior is undefined when \a pos < 0 or \a pos > size().
 //! [UB-sliced-index-only]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
+*/
+
+/*!
+    \fn QLatin1StringView &QLatin1StringView::slice(qsizetype pos, qsizetype n)
+    \since 6.8
+    \overload
+
+    Modifies this Latin-1 string view to start at position \a pos,
+    extending for \a n characters.
+
+    \include qlatin1stringview.qdoc UB-sliced-index-length
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
+*/
+
+/*!
+    \fn QLatin1StringView &QLatin1StringView::slice(qsizetype pos)
+    \since 6.8
+
+    Modifies this Latin-1 string view to start at position \a pos, extending
+    to its end.
+
+    \include qlatin1stringview.qdoc UB-sliced-index-only
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
 */
 
 /*!
@@ -807,7 +832,7 @@
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa sliced(), first(), last(), chop(), truncate()
+    \sa sliced(), first(), last(), chop(), truncate(), slice()
 */
 
 /*!
@@ -833,7 +858,7 @@
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa sliced(), first(), last(), chopped(), truncate()
+    \sa sliced(), first(), last(), chopped(), truncate(), slice()
 */
 
 /*!

src/corelib/text/qstringview.cpp

@@ -592,7 +592,7 @@ QT_BEGIN_NAMESPACE
     \a length is negative (default), the function returns all characters that
     are available from \a start.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -606,7 +606,7 @@ QT_BEGIN_NAMESPACE
     The entire string view is returned if \a length is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), startsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -620,7 +620,7 @@ QT_BEGIN_NAMESPACE
     The entire string view is returned if \a length is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), endsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -632,7 +632,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa last(), sliced(), startsWith(), chopped(), chop(), truncate()
+    \sa last(), sliced(), startsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -644,7 +644,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa first(), sliced(), endsWith(), chopped(), chop(), truncate()
+    \sa first(), sliced(), endsWith(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -659,7 +659,7 @@ QT_BEGIN_NAMESPACE
     or \a pos + \a n > size().
 //! [UB-sliced-index-length]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -674,7 +674,32 @@ QT_BEGIN_NAMESPACE
     \note The behavior is undefined when \a pos < 0 or \a pos > size().
 //! [UB-sliced-index-only]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
+*/
+
+/*!
+    \fn QStringView &QStringView::slice(qsizetype pos, qsizetype n)
+    \since 6.8
+
+    Modifies this string view to start from position \a pos, extending
+    for \a n code points.
+
+    \include qstringview.cpp UB-sliced-index-length
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
+*/
+
+/*!
+    \fn QStringView &QStringView::slice(qsizetype pos)
+    \since 6.8
+    \overload
+
+    Modifies this string view to start from position \a pos, extending
+    to its end.
+
+    \include qstringview.cpp UB-sliced-index-only
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
 */
 
 /*!
@@ -687,7 +712,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa mid(), left(), right(), chop(), truncate()
+    \sa mid(), left(), right(), chop(), truncate(), slice()
 */
 
 /*!
@@ -711,7 +736,7 @@ QT_BEGIN_NAMESPACE
 
     \note The behavior is undefined when \a length < 0 or \a length > size().
 
-    \sa mid(), left(), right(), chopped(), truncate()
+    \sa mid(), left(), right(), chopped(), truncate(), slice()
 */
 
 /*!

src/corelib/text/qstringview.h

@@ -237,6 +237,11 @@ public:
 
     [[nodiscard]] QStringView trimmed() const noexcept { return QtPrivate::trimmed(*this); }
 
+    constexpr QStringView &slice(qsizetype pos)
+    { *this = sliced(pos); return *this; }
+    constexpr QStringView &slice(qsizetype pos, qsizetype n)
+    { *this = sliced(pos, n); return *this; }
+
     template <typename Needle, typename...Flags>
     [[nodiscard]] constexpr inline auto tokenize(Needle &&needle, Flags...flags) const
         noexcept(noexcept(qTokenize(std::declval<const QStringView&>(), std::forward<Needle>(needle), flags...)))

src/corelib/text/qutf8stringview.h

@@ -247,6 +247,11 @@ public:
     [[nodiscard]] constexpr QBasicUtf8StringView chopped(qsizetype n) const
     { verify(0, n); return sliced(0, m_size - n); }
 
+    constexpr QBasicUtf8StringView &slice(qsizetype pos)
+    { *this = sliced(pos); return *this; }
+    constexpr QBasicUtf8StringView &slice(qsizetype pos, qsizetype n)
+    { *this = sliced(pos, n); return *this; }
+
     constexpr void truncate(qsizetype n)
     { verify(0, n); m_size = n; }
     constexpr void chop(qsizetype n)

src/corelib/text/qutf8stringview.qdoc

@@ -555,7 +555,7 @@
     \a n is negative (default), the function returns all code points that
     are available from \a pos.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -569,7 +569,7 @@
     The entire string view is returned if \a n is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -583,7 +583,7 @@
     The entire string view is returned if \a n is greater than or equal
     to size(), or less than zero.
 
-    \sa first(), last(), sliced(), chopped(), chop(), truncate()
+    \sa first(), last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -594,7 +594,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa last(), sliced(), chopped(), chop(), truncate()
+    \sa last(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -604,7 +604,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa first(), sliced(), chopped(), chop(), truncate()
+    \sa first(), sliced(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -618,7 +618,7 @@
     or \a pos + \a n > size().
 //! [UB-sliced-index-length]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
 */
 
 /*!
@@ -631,7 +631,32 @@
     \note The behavior is undefined when \a pos < 0 or \a pos > size().
 //! [UB-sliced-index-only]
 
-    \sa first(), last(), chopped(), chop(), truncate()
+    \sa first(), last(), chopped(), chop(), truncate(), slice()
+*/
+
+/*!
+    \fn QUtf8StringView &QUtf8StringView::slice(qsizetype pos, qsizetype n)
+    \since 6.8
+
+    Modifies this string view to start at position \a pos, extending for
+    \a n code points.
+
+    \include qutf8stringview.qdoc UB-sliced-index-length
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
+*/
+
+/*!
+    \fn QUtf8StringView &QUtf8StringView::slice(qsizetype pos)
+    \since 6.8
+    \overload
+
+    Modifies this string view to start at position \a pos, extending
+    to its end.
+
+    \include qutf8stringview.qdoc UB-sliced-index-only
+
+    \sa sliced(), first(), last(), chopped(), chop(), truncate()
 */
 
 /*!
@@ -644,7 +669,7 @@
 
     \note The behavior is undefined when \a n < 0 or \a n > size().
 
-    \sa sliced(), first(), last(), chop(), truncate()
+    \sa sliced(), first(), last(), chop(), truncate(), slice()
 */
 
 /*!

tests/auto/corelib/text/qstringapisymmetry/tst_qstringapisymmetry.cpp

@@ -741,9 +741,9 @@ private:
     void right_data();
     template <typename String> void right_impl();
 
+    // Tests both sliced() and slice()
     void sliced_data();
     template <typename String> void sliced_impl();
-    template <typename String> void slice_impl();
 
     void first_data();
     template <typename String> void first_impl();
@@ -832,11 +832,6 @@ private Q_SLOTS:
     void sliced_QByteArrayView_data() { sliced_data(); }
     void sliced_QByteArrayView() { sliced_impl<QByteArrayView>(); }
 
-    void slice_QString_data() { sliced_data(); }
-    void slice_QString() { slice_impl<QString>(); }
-    void slice_QByteArray_data() { sliced_data(); }
-    void slice_QByteArray() { slice_impl<QByteArray>(); }
-
     void first_truncate_QString_data() { first_data(); }
     void first_truncate_QString() { first_impl<QString>(); }
     void first_truncate_QStringView_data() { first_data(); }
@@ -2564,27 +2559,17 @@ void tst_QStringApiSymmetry::sliced_impl()
         QCOMPARE_EQ(sliced.isNull(), result2.isNull());
         QCOMPARE_EQ(sliced.isEmpty(), result2.isEmpty());
     }
-}
 
-template <typename String>
+    {
-void tst_QStringApiSymmetry::slice_impl()
+        auto str = s;
-{
+        str.slice(pos);
-    QFETCH(const QStringView, unicode);
+        QCOMPARE_EQ(str, result);
-    QFETCH(const QLatin1String, latin1);
+    }
-    QFETCH(const int, pos);
+    {
-    QFETCH(const int, n);
+        auto str = s;
-    QFETCH(const QAnyStringView, result);
+        str.slice(pos, n);
-    QFETCH(const QAnyStringView, result2);
+        QCOMPARE_EQ(str, result2);
-
+    }
-    const auto str = make<String>(unicode, latin1, unicode.toUtf8());
-
-    auto s = str;
-    s.slice(pos);
-    QCOMPARE_EQ(s, result);
-
-    s = str;
-    s.slice(pos, n);
-    QCOMPARE_EQ(s, result2);
 }
 
 void tst_QStringApiSymmetry::first_data()