RunTaskDialog: validate executable before accepting

src/runtaskdialog.cpp

@@ -24,8 +24,11 @@
 #include <QDir>
 #include <QFileDialog>
 #include <QFileInfo>
+#include <QLabel>
 #include <QLineEdit>
 #include <QPushButton>
+#include <QStandardPaths>
+#include <QVBoxLayout>
 
 RunTaskDialog::RunTaskDialog(QWidget *parent) : QDialog(parent), ui(new Ui::RunTaskDialog)
 {
@@ -37,11 +40,23 @@ RunTaskDialog::RunTaskDialog(QWidget *parent) : QDialog(parent), ui(new Ui::RunT
 
     this->m_okButton = this->ui->buttonBox->button(QDialogButtonBox::Ok);
 
-    connect(this->ui->buttonBox, &QDialogButtonBox::accepted, this, &QDialog::accept);
+    this->m_errorLabel = new QLabel(this);
+    this->m_errorLabel->setWordWrap(true);
+    this->m_errorLabel->setVisible(false);
+
+    auto *layout = qobject_cast<QVBoxLayout *>(this->layout());
+    if (layout)
+    {
+        const int buttonBoxIndex = layout->indexOf(this->ui->buttonBox);
+        layout->insertWidget(buttonBoxIndex, this->m_errorLabel);
+    }
+
+    connect(this->ui->buttonBox, &QDialogButtonBox::accepted, this, &RunTaskDialog::accept);
     connect(this->ui->buttonBox, &QDialogButtonBox::rejected, this, &QDialog::reject);
     connect(this->ui->browseButton, &QPushButton::clicked, this, &RunTaskDialog::browseForCommand);
     connect(this->ui->commandCombo->lineEdit(), &QLineEdit::textChanged, this, [this]()
     {
+        this->m_errorLabel->setVisible(false);
         this->updateOkButton();
     });
 
@@ -79,6 +94,81 @@ void RunTaskDialog::updateOkButton()
         this->m_okButton->setEnabled(!this->Command().isEmpty());
 }
 
+void RunTaskDialog::accept()
+{
+    const QString command = this->Command();
+    if (command.isEmpty())
+        return;
+
+    const QString exe = RunTaskDialog::resolveExecutable(command);
+    if (exe.isEmpty())
+    {
+        // clamped to avoid blowing up the dialog
+        QString program = command.split(' ', Qt::SkipEmptyParts).value(0);
+        constexpr int maxLen = 40;
+        if (program.size() > maxLen)
+            program = program.left(maxLen) + QStringLiteral("\u2026"); // '…'
+        this->setError(tr("Program or file \u201c%1\u201d does not exist or could not be found.").arg(program));
+        return;
+    }
+
+    QDialog::accept();
+}
+
+void RunTaskDialog::setError(const QString &message)
+{
+    if (!this->m_errorLabel)
+        return;
+    this->m_errorLabel->setText(QStringLiteral("\u26a0 ") + message);
+    if (!this->m_errorLabel->isVisible())
+    {
+        this->m_errorLabel->setVisible(true);
+        const QSize hint = this->sizeHint();
+        if (hint.height() > this->height())
+            this->resize(this->width(), hint.height());
+    }
+}
+
+QString RunTaskDialog::resolveExecutable(const QString &command)
+{
+    if (command.trimmed().isEmpty())
+        return {};
+
+    // Grab the first token
+    QString token = command.trimmed();
+
+    // Handle single-quoted token
+    if (token.startsWith('\''))
+    {
+        const int end = token.indexOf('\'', 1);
+        token = (end > 0) ? token.mid(1, end - 1) : token.mid(1);
+    }
+    // Handle double-quoted token
+    else if (token.startsWith('"'))
+    {
+        const int end = token.indexOf('"', 1);
+        token = (end > 0) ? token.mid(1, end - 1) : token.mid(1);
+    }
+    else
+    {
+        // Take everything up to the first whitespace
+        token = token.split(' ', Qt::SkipEmptyParts).value(0);
+    }
+
+    if (token.isEmpty())
+        return {};
+
+    // Check if the token contains a path separator
+    if (token.contains('/') || token.startsWith('.'))
+    {
+        const QFileInfo fi(token);
+        return fi.exists() ? fi.absoluteFilePath() : QString{};
+    }
+
+    // Else look it up on PATH
+    return QStandardPaths::findExecutable(token);
+}
+
 QString RunTaskDialog::shellQuote(const QString &text)
 {
     QString escaped = text;

src/runtaskdialog.h

@@ -24,6 +24,7 @@
 QT_BEGIN_NAMESPACE
 namespace Ui { class RunTaskDialog; }
 class QPushButton;
+class QLabel;
 QT_END_NAMESPACE
 
 class RunTaskDialog : public QDialog
@@ -37,12 +38,16 @@ class RunTaskDialog : public QDialog
         QString Command() const;
 
     private:
+        void accept() override;
         void browseForCommand();
         void updateOkButton();
+        void setError(const QString &message);
         static QString shellQuote(const QString &text);
+        static QString resolveExecutable(const QString &command);
 
         Ui::RunTaskDialog *ui { nullptr };
         QPushButton *m_okButton { nullptr };
+        QLabel *m_errorLabel { nullptr };
 };
 
 #endif // RUNTASKDIALOG_H