fix(rules): keep the text-mode toggle reachable

Ticking "Edit as text" was a one-way trip: the only way back to the rows
was closing the dialog and reopening it. The checkbox was parented to the
builder widget and sat on the match row, and switching to text mode hides
that widget, so the toggle disappeared along with the rows it governs.

Move it to the query row, which is visible in both modes.

The existing tests all passed against this, because they drove the toggle
through setChecked and then asserted on the checked STATE. A hidden
checkbox reports its state perfectly well, so every one of those
assertions held while the widget was unreachable. The new test asks the
question that matters, whether the toggle would be on screen, and it uses
isVisibleTo since nothing is isVisible on a dialog that was never shown.

Worth recording how close the mutation check came to endorsing this too.
Reparenting the checkbox alone left it in the query row's layout, so it
stayed visible and the test still passed. Only restoring the full shipped
shape, parent and layout together, reproduced the fault and failed the
test. A mutation that does not reproduce the original bug proves nothing
about the test that is meant to catch it.

The spec's layout sketch carried the same error and is corrected, with
the reason, so the next reader does not reintroduce it.

1 files changed, 23 insertions, 6 deletions

diff --git a/src/tagrulesdialog.cpp b/src/tagrulesdialog.cpp
index c81450c..75a9cbe 100644
--- a/src/tagrulesdialog.cpp
+++ b/src/tagrulesdialog.cpp
@@ -131,14 +131,9 @@ TagRulesDialog::TagRulesDialog(QWidget *parent)
     auto *matchGroup = new QButtonGroup(this);
     matchGroup->addButton(m_matchAll);
     matchGroup->addButton(m_matchAny);
-    m_textMode = new QCheckBox(tr("Edit as &text"), m_builder);
-    m_textMode->setToolTip(
-        tr("Edit the notmuch query directly. A rule too complex to show as "
-           "rows opens this way."));
     matchRow->addWidget(m_matchAll);
     matchRow->addWidget(m_matchAny);
     matchRow->addStretch();
-    matchRow->addWidget(m_textMode);
     builderLayout->addLayout(matchRow);
 
     m_rowsLayout = new QVBoxLayout;
@@ -153,7 +148,21 @@ TagRulesDialog::TagRulesDialog(QWidget *parent)
     builderLayout->addWidget(m_addExclusion, 0, Qt::AlignLeft);
 
     form->addRow(tr("Match"), m_builder);
-    form->addRow(tr("Query"), m_query);
+
+    // The toggle sits with the QUERY line, not inside m_builder, because
+    // switching to text mode HIDES m_builder. A checkbox parented there
+    // vanishes with the rows it governs, leaving no way back except closing
+    // the dialog, which is exactly what shipped in the first draft of this
+    // builder. The query row is visible in both modes, so the toggle is
+    // always reachable.
+    auto *queryRow = new QHBoxLayout;
+    m_textMode = new QCheckBox(tr("Edit as &text"), this);
+    m_textMode->setToolTip(
+        tr("Edit the notmuch query directly. A rule too complex to show as "
+           "rows opens this way."));
+    queryRow->addWidget(m_query, 1);
+    queryRow->addWidget(m_textMode);
+    form->addRow(tr("Query"), queryRow);
 
     // The query line shows what the rows compile to. Read-only in builder
     // mode: it is what actually ships to the hook, and watching it change is
@@ -475,6 +484,14 @@ void TagRulesDialog::setTextModeForTest(bool on)
     m_textMode->setChecked(on);
 }
 
+bool TagRulesDialog::textModeToggleIsReachableForTest() const
+{
+    // isVisibleTo rather than isVisible: nothing is isVisible() on a dialog
+    // that was never shown, so that would report unreachable in both the
+    // working and the broken case.
+    return m_textMode->isVisibleTo(this);
+}
+
 QString TagRulesDialog::warningTextForTest() const
 {
     // isVisible() is false for every child of a dialog that was never shown,