qmlformat: Don't add extra commas to holed arrays

`[1, 2, 3, 4, , ,]` is parsed with the comma that comes before the
trailing holes stored on two different nodes: on the ArrayPattern, and
on the list element that wraps those holes. The formatter wrote both, so
every pass over the file appended another hole to the array. That
changes the semantics of the expression.

Store the comma on the ArrayPattern only if it isn't already part of the
elision.

This also ensures missing spaces between commas in the array.

Amends d41f97e86702d8c5ac81a4246e1aab8dd965cbe4

Task-number: QTBUG-151040
Pick-to: 6.12
Change-Id: Ied05c0100210b0b2d06cf69a4fe55ee565239730
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

5 files changed, 16 insertions, 5 deletions

diff --git a/src/qml/parser/qqmljs.g b/src/qml/parser/qqmljs.g
index 8f0cfe4fe1..c64e24fa62 100644
--- a/src/qml/parser/qqmljs.g
+++ b/src/qml/parser/qqmljs.g
@@ -2115,7 +2115,8 @@ ArrayLiteral: T_LBRACKET ElementList T_COMMA ElisionOpt T_RBRACKET;
         }
         AST::ArrayPattern *node = new (pool) AST::ArrayPattern(list->finish());
         node->lbracketToken = loc(1);
-        node->commaToken = loc(3);
+        if (!sym(4).Elision)
+            node->commaToken = loc(3);
         node->rbracketToken = loc(5);
         sym(1).Node = node;
         Q_ASSERT(node->isValidArrayLiteral());
diff --git a/src/qmldom/qqmldomreformatter.cpp b/src/qmldom/qqmldomreformatter.cpp
index d1c70d47c5..266e075ab1 100644
--- a/src/qmldom/qqmldomreformatter.cpp
+++ b/src/qmldom/qqmldomreformatter.cpp
@@ -170,8 +170,11 @@ bool ScriptFormatter::visit(PatternElementList *ast)
         if (isObjectInitializer)
             ensureNewline();
 
-        if (it->elision)
+        if (it->elision) {
             accept(it->elision);
+            if (it->element)
+                ensureSpaceIfNoComment();
+        }
         if (it->element)
             accept(it->element);
         if (it->next) {
@@ -897,10 +900,11 @@ bool ScriptFormatter::visit(FunctionExpression *ast)
 bool ScriptFormatter::visit(Elision *ast)
 {
     for (Elision *it = ast; it; it = it->next) {
-        if (it->commaToken.isValid()) {
-            outWithComments(it->commaToken, it);
+        if (!it->commaToken.isValid())
+            continue;
+        outWithComments(it->commaToken, it);
+        if (it->next)
             ensureSpaceIfNoComment();
-        }
     }
     return false;
 }
diff --git a/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.formatted.js b/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.formatted.js
new file mode 100644
index 0000000000..7b79ac117c
--- /dev/null
+++ b/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.formatted.js
@@ -0,0 +1 @@
+[1, , , , [1, 2, 3], ,];
diff --git a/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.js b/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.js
new file mode 100644
index 0000000000..78b5ed7b8a
--- /dev/null
+++ b/tests/auto/qml/qmlformat/data/holedArrayExtraCommas.js
@@ -0,0 +1,3 @@
+
+
+[1, , , , [1, 2, 3], ,];
diff --git a/tests/auto/qml/qmlformat/tst_qmlformat.cpp b/tests/auto/qml/qmlformat/tst_qmlformat.cpp
index 0305a2018e..17a2b1cbdc 100644
--- a/tests/auto/qml/qmlformat/tst_qmlformat.cpp
+++ b/tests/auto/qml/qmlformat/tst_qmlformat.cpp
@@ -119,6 +119,8 @@ void TestQmlformat::plainJS_data()
                                        << "longStatementList.formatted.js";
     QTest::newRow("elisionCommaConfusion") << "elisionCommaConfusion.js"
                                            << "elisionCommaConfusion.formatted.js";
+    QTest::newRow("holedArrayExtraCommas") << "holedArrayExtraCommas.js"
+                                           << "holedArrayExtraCommas.formatted.js";
 }
 
 void TestQmlformat::plainJS()