[ENH] textimport: Mark encoding errors in the preview

Orange/widgets/data/owcsvimport.py

@@ -579,21 +579,32 @@ def selectedFileFormat(self) -> FileFormat:
 
 def default_options_for_mime_type(
         path: str, mime_type: str
-) -> Tuple[csv.Dialect, bool]:
+) -> Options:
     defaults = {
         "text/csv": (csv.excel(), True),
         "text/tab-separated-values": (csv.excel_tab(), True)
     }
-    dialect, header = csv.excel(), True
+    dialect, header, encoding = csv.excel(), True, "utf-8"
     delimiters = None
+    try_encodings = ["utf-8", "utf-16", "iso8859-1"]
     if mime_type in defaults:
         dialect, header = defaults[mime_type]
         delimiters = [dialect.delimiter]
-    try:
-        dialect, header = sniff_csv_with_path(path, delimiters=delimiters)
-    except (OSError, UnicodeDecodeError, csv.Error):
-        pass
-    return dialect, header
+
+    for encoding_ in try_encodings:
+        try:
+            dialect, header = sniff_csv_with_path(
+                path, encoding=encoding_, delimiters=delimiters)
+            encoding = encoding_
+        except (OSError, UnicodeError, csv.Error):
+            pass
+        else:
+            break
+    if header:
+        rowspec = [(range(0, 1), RowSpec.Header)]
+    else:
+        rowspec = []
+    return Options(dialect=dialect, encoding=encoding, rowspec=rowspec)
 
 
 class OWCSVFileImport(widget.OWWidget):
@@ -910,11 +921,10 @@ def browse(self, prefixname=None, directory=None):
                 mb = self._might_be_binary_mb(path)
                 if mb.exec() == QMessageBox.Cancel:
                     return
-            # initialize dialect based on selected format
-            dialect, header = default_options_for_mime_type(
+            # initialize options based on selected format
+            options = default_options_for_mime_type(
                 path, selected_filter.mime_type,
             )
-            options = None
             # Search for path in history.
             # If found use the stored params to initialize the import dialog
             items = self.itemsFromSettings()
@@ -923,15 +933,6 @@ def browse(self, prefixname=None, directory=None):
                 _, options_ = items[idx]
                 if options_ is not None:
                     options = options_
-
-            if options is None:
-                if not header:
-                    rowspec = []
-                else:
-                    rowspec = [(range(0, 1), RowSpec.Header)]
-                options = Options(
-                    encoding="utf-8", dialect=dialect, rowspec=rowspec)
-
             dlg = CSVImportDialog(
                 self, windowTitle="Import Options", sizeGripEnabled=True)
             dlg.setWindowModality(Qt.WindowModal)

Orange/widgets/utils/textimport.py

@@ -991,9 +991,11 @@ def __resetPreview(self):
             base = CachedBytesIOWrapper(self.__sample, self.__buffer)
 
         wrapper = io.TextIOWrapper(
-            base, encoding=self.encoding(), errors="replace"
+            base, encoding=self.encoding(),
+            # use surrogate escape to validate/detect encoding errors in
+            # delegates
+            errors="surrogateescape"
         )
-
         rows = csv.reader(
             wrapper, dialect=self.dialect()
         )
@@ -1372,6 +1374,11 @@ def sizeHint(self):
         return sh.expandedTo(QSize(8 * hsection, 20 * vsection))
 
 
+def is_surrogate_escaped(text: str) -> bool:
+    """Does `text` contain any surrogate escape characters."""
+    return any("\udc80" <= c <= "\udcff" for c in text)
+
+
 class PreviewItemDelegate(QStyledItemDelegate):
     def initStyleOption(self, option, index):
         # type: (QStyleOptionViewItem, QModelIndex) -> None
@@ -1389,6 +1396,18 @@ def initStyleOption(self, option, index):
         if coltype == ColumnType.Numeric or coltype == ColumnType.Time:
             option.displayAlignment = Qt.AlignRight | Qt.AlignVCenter
 
+        if not self.validate(option.text):
+            option.palette.setBrush(
+                QPalette.All, QPalette.Text, QBrush(Qt.red, Qt.SolidPattern)
+            )
+            option.palette.setBrush(
+                QPalette.All, QPalette.HighlightedText,
+                QBrush(Qt.red, Qt.SolidPattern)
+            )
+
+    def validate(self, value: str) -> bool:  # pylint: disable=no-self-use
+        return not is_surrogate_escaped(value)
+
     def helpEvent(self, event, view, option, index):
         # type: (QHelpEvent, QAbstractItemView, QStyleOptionViewItem, QModelIndex) -> bool
         if event.type() == QEvent.ToolTip:
@@ -1467,17 +1486,6 @@ def __init__(self, *args, converter=None, **kwargs):
         super().__init__(*args, **kwargs)
         self.converter = converter or float
 
-    def initStyleOption(self, option, index):
-        super().initStyleOption(option, index)
-        if not self.validate(option.text):
-            option.palette.setBrush(
-                QPalette.All, QPalette.Text, QBrush(Qt.red, Qt.SolidPattern)
-            )
-            option.palette.setBrush(
-                QPalette.All, QPalette.HighlightedText,
-                QBrush(Qt.red, Qt.SolidPattern)
-            )
-
     def validate(self, value):
         if value in {"NA", "Na", "na", "n/a", "N/A", "?", "", "."}:
             return True
@@ -1486,7 +1494,7 @@ def validate(self, value):
         except ValueError:
             return False
         else:
-            return True
+            return super().validate(value)
 
 
 def number_parser(groupsep, decimalsep):