add $$take_first() and $$take_last() functions

while implementing stacks and queues was possible before with the help
of $$member(), these functions make it much more straight-forward.

[ChangeLog][qmake] Added $$take_first() and $$take_last() functions.

Change-Id: I4922a5331780e468a42c663c9ad3c6456a95a6bf
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

qmake/doc/src/qmake-manual.qdoc

@@ -2847,6 +2847,7 @@
     MY_VAR2 will contain '-Lone -Ltwo -Lthree -Lfour -Lfive', and MY_VAR3 will
     contain 'three two three'.
 
+    \target fn_first
     \section2 first(variablename)
 
     Returns the first value of \c variablename.
@@ -2855,7 +2856,7 @@
 
     \snippet code/doc_src_qmake-manual.pro 161
 
-    See also \l{last(variablename)}{last()}.
+    See also \l{take_first()}, \l{fn_last}{last()}.
 
     \section2 format_number(number[, options...])
 
@@ -2903,6 +2904,7 @@
     to empty strings. If you need to encode spaces in \c glue, \c before, or \c
     after, you must quote them.
 
+    \target fn_last
     \section2 last(variablename)
 
     Returns the last value of \c variablename.
@@ -2911,7 +2913,7 @@
 
     \snippet code/doc_src_qmake-manual.pro 162
 
-    See also \l{first(variablename)}{first()}.
+    See also \l{take_last()}, \l{fn_first}{first()}.
 
     \section2 list(arg1 [, arg2 ..., argn])
 
@@ -3063,6 +3065,26 @@
 
     See also \l{shell_quote(arg)}{shell_quote()}.
 
+    \target take_first()
+    \section2 take_first(variablename)
+
+    Returns the first value of \c variablename and removes it from the
+    source variable.
+
+    This provides convenience for implementing queues, for example.
+
+    See also \l{take_last()}, \l{fn_first}{first()}.
+
+    \target take_last()
+    \section2 take_last(variablename)
+
+    Returns the last value of \c variablename and removes it from the
+    source variable.
+
+    This provides convenience for implementing stacks, for example.
+
+    See also \l{take_first()}, \l{fn_last}{last()}.
+
     \target unique
     \section2 unique(variablename)
 

qmake/library/qmakebuiltins.cpp

@@ -80,7 +80,8 @@ QT_BEGIN_NAMESPACE
 #define fL1S(s) QString::fromLatin1(s)
 
 enum ExpandFunc {
-    E_INVALID = 0, E_MEMBER, E_FIRST, E_LAST, E_SIZE, E_CAT, E_FROMFILE, E_EVAL, E_LIST,
+    E_INVALID = 0, E_MEMBER, E_FIRST, E_TAKE_FIRST, E_LAST, E_TAKE_LAST, E_SIZE,
+    E_CAT, E_FROMFILE, E_EVAL, E_LIST,
     E_SPRINTF, E_FORMAT_NUMBER, E_JOIN, E_SPLIT, E_BASENAME, E_DIRNAME, E_SECTION,
     E_FIND, E_SYSTEM, E_UNIQUE, E_REVERSE, E_QUOTE, E_ESCAPE_EXPAND,
     E_UPPER, E_LOWER, E_TITLE, E_FILES, E_PROMPT, E_RE_ESCAPE, E_VAL_ESCAPE,
@@ -105,7 +106,9 @@ void QMakeEvaluator::initFunctionStatics()
     } expandInits[] = {
         { "member", E_MEMBER },
         { "first", E_FIRST },
+        { "take_first", E_TAKE_FIRST },
         { "last", E_LAST },
+        { "take_last", E_TAKE_LAST },
         { "size", E_SIZE },
         { "cat", E_CAT },
         { "fromfile", E_FROMFILE },
@@ -690,6 +693,20 @@ ProStringList QMakeEvaluator::evaluateBuiltinExpand(
             }
         }
         break;
+    case E_TAKE_FIRST:
+    case E_TAKE_LAST:
+        if (args.count() != 1) {
+            evalError(fL1S("%1(var) requires one argument.").arg(func.toQString(m_tmp1)));
+        } else {
+            ProStringList &var = valuesRef(map(args.at(0)));
+            if (!var.isEmpty()) {
+                if (func_t == E_TAKE_FIRST)
+                    ret.append(var.takeFirst());
+                else
+                    ret.append(var.takeLast());
+            }
+        }
+        break;
     case E_SIZE:
         if (args.count() != 1)
             evalError(fL1S("size(var) requires one argument."));

tests/auto/tools/qmakelib/evaltest.cpp

@@ -742,6 +742,30 @@ void tst_qmakelib::addReplaceFunctions(const QString &qindir)
             << "##:1: first(var) requires one argument."
             << true;
 
+    QTest::newRow("$$take_first(): empty")
+            << "IN = \nVAR = $$take_first(IN)"
+            << "VAR =\nIN ="
+            << ""
+            << true;
+
+    QTest::newRow("$$take_first(): one")
+            << "IN = one\nVAR = $$take_first(IN)"
+            << "VAR = one\nIN ="
+            << ""
+            << true;
+
+    QTest::newRow("$$take_first(): multiple")
+            << "IN = one two three\nVAR = $$take_first(IN)"
+            << "VAR = one\nIN = two three"
+            << ""
+            << true;
+
+    QTest::newRow("$$take_first(): bad number of arguments")
+            << "VAR = $$take_first(1, 2)"
+            << "VAR ="
+            << "##:1: take_first(var) requires one argument."
+            << true;
+
     QTest::newRow("$$last(): empty")
             << "IN = \nVAR = $$last(IN)"
             << "VAR ="
@@ -766,6 +790,30 @@ void tst_qmakelib::addReplaceFunctions(const QString &qindir)
             << "##:1: last(var) requires one argument."
             << true;
 
+    QTest::newRow("$$take_last(): empty")
+            << "IN = \nVAR = $$take_last(IN)"
+            << "VAR =\nIN ="
+            << ""
+            << true;
+
+    QTest::newRow("$$take_last(): one")
+            << "IN = one\nVAR = $$take_last(IN)"
+            << "VAR = one\nIN ="
+            << ""
+            << true;
+
+    QTest::newRow("$$take_last(): multiple")
+            << "IN = one two three\nVAR = $$take_last(IN)"
+            << "VAR = three\nIN = one two"
+            << ""
+            << true;
+
+    QTest::newRow("$$take_last(): bad number of arguments")
+            << "VAR = $$take_last(1, 2)"
+            << "VAR ="
+            << "##:1: take_last(var) requires one argument."
+            << true;
+
     QTest::newRow("$$size()")
             << "IN = one two three\nVAR = $$size(IN)"
             << "VAR = 3"