Backport PR #23524 on branch 6.x (PR : Add validation for theme color…

… changes (Preferences)) (#23579)

spyder/plugins/appearance/widgets.py

@@ -6,9 +6,19 @@
 
 """Appearance entry in Preferences."""
 
+import re
+
 from qtpy.QtCore import Qt
-from qtpy.QtWidgets import (QDialog, QDialogButtonBox, QGridLayout, QGroupBox,
-                            QHBoxLayout, QVBoxLayout, QWidget)
+from qtpy.QtWidgets import (
+    QDialog,
+    QDialogButtonBox,
+    QGridLayout,
+    QGroupBox,
+    QHBoxLayout,
+    QMessageBox,
+    QVBoxLayout,
+    QWidget,
+)
 
 from spyder.api.translations import _
 from spyder.api.widgets.dialogs import SpyderDialogButtonBox
@@ -42,7 +52,7 @@ def __init__(self, parent=None, stack=None):
         self.setLayout(layout)
 
         # Signals
-        bbox.accepted.connect(self.accept)
+        bbox.accepted.connect(self.validate_colors)
         bbox.accepted.connect(self.get_edited_color_scheme)
         bbox.rejected.connect(self.reject)
 
@@ -60,6 +70,43 @@ def get_scheme_name(self):
         """
         return self.scheme_name_textbox[self.last_used_scheme].text()
 
+    def validate_colors(self):
+        """
+        Validate the current color scheme and display a message box listing
+        any invalid colors.
+        """
+        invalid_colors = {}
+        scheme_name = self.last_used_scheme
+        pattern = (
+            r"^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3}|[A-Fa-f0-9]{8}|[A-Fa-f0-9]{4})$"
+        )
+        for key in self.widgets[scheme_name]:
+            items = self.widgets[scheme_name][key]
+
+            if not bool(re.match(pattern, items[0].text())):
+                invalid_colors[key] = items[0].text()
+
+        if invalid_colors:
+            message = _("The following properties have invalid colors:\n\n")
+            for property_name, color in invalid_colors.items():
+                name = syntaxhighlighters.COLOR_SCHEME_KEYS[property_name]
+                clean_name = name[:-1].replace("<br>", "")
+                message += _(
+                    "The property <b>{}</b> has an invalid color: {}\n"
+                ).format(clean_name, color)
+
+            msgbox = QMessageBox(
+                QMessageBox.Warning,
+                _('Error setting colors'),
+                message,
+                QMessageBox.Ok,
+                self
+            )
+            msgbox.exec_()
+        else:
+            self.accept()
+
+
     def get_edited_color_scheme(self):
         """
         Get the values of the last edited color scheme to be used in an instant