findinfiles: Ignore exclude regexp if it's empty

If the exclude regexp is empty, don't try to compile it. Change
SearchThread so an empty string will make no file be excluded
from the search.

This fixes issue spyder-ide#7811 when exclude_re is true.

Signed-off-by: Eduardo Habkost <ehabkost@raisama.net>

spyder/widgets/findinfiles.py

@@ -101,7 +101,8 @@ def initialize(self, path, is_file, exclude,
         self.rootpath = path
         self.python_path = False
         self.hg_manifest = False
-        self.exclude = re.compile(exclude)
+        if exclude:
+            self.exclude = re.compile(exclude)
         self.texts = texts
         self.text_re = text_re
         self.is_file = is_file
@@ -143,14 +144,14 @@ def find_files_in_path(self, path):
                         if self.stopped:
                             return False
                     dirname = os.path.join(path, d)
-                    if re.search(self.exclude, dirname + os.sep):
+                    if self.exclude and re.search(self.exclude, dirname + os.sep):
                         dirs.remove(d)
                 for f in files:
                     with QMutexLocker(self.mutex):
                         if self.stopped:
                             return False
                     filename = os.path.join(path, f)
-                    if re.search(self.exclude, filename):
+                    if self.exclude and re.search(self.exclude, filename):
                         continue
                     if is_text_file(filename):
                         self.find_string_in_file(filename)
@@ -565,7 +566,8 @@ def get_options(self, all=False):
         # Validate regular expressions:
 
         try:
-            exclude = re.compile(exclude)
+            if exclude:
+                exclude = re.compile(exclude)
         except Exception:
             exclude_edit = self.exclude_pattern.lineEdit()
             exclude_edit.setStyleSheet(self.REGEX_INVALID)