Fix `TextCanvas` `CanvasError("Attribute extends beyond text...")` (#555)HEADmaster

* Fix TextCanvas `CanvasError("Attribute extends beyond text...")

* `[[]] * ...` causes
  list of 1 list with pointers
  amount equal to multiplier
  instead of "list of lists"
* Add 2 basic font tests which check for Canvas create issue
* Add few type annotations during debug process

Fix: #554

* Force tests to restore default encoding in tearDown

Tests order change should not cause tests failures

---------

Co-authored-by: Aleksei Stepanov <alekseis@nvidia.com>

6 files changed, 147 insertions, 24 deletions

diff --git a/urwid/tests/test_canvas.py b/urwid/tests/test_canvas.py
index 5a1d454..d0c624c 100644
--- a/urwid/tests/test_canvas.py
+++ b/urwid/tests/test_canvas.py
@@ -302,6 +302,12 @@ class CanvasJoinTest(unittest.TestCase):
 
 
 class CanvasOverlayTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def cotest(self, desc, bgt, bga, fgt, fga, l, r, et):
         bgt = bgt.encode('iso8859-1')
         fgt = fgt.encode('iso8859-1')
diff --git a/urwid/tests/test_font.py b/urwid/tests/test_font.py
new file mode 100644
index 0000000..3c9be7a
--- /dev/null
+++ b/urwid/tests/test_font.py
@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import unittest
+
+import urwid
+
+
+class TestFontRender(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
+    def test_001_basic(self):
+        font = urwid.Thin3x3Font()
+        rendered = b'\n'.join(font.render("1").text).decode()
+        expected = ' ┐ \n │ \n ┴ '
+        self.assertEqual(expected, rendered)
+
+    def test_002_non_rect(self):
+        """Test non rect symbol, which causes spaces based padding.
+
+        Lines as bytes should be not equal length.
+        """
+        font = urwid.Thin3x3Font()
+        rendered = b'\n'.join(font.render("2").text).decode()
+        expected = '┌─┐\n┌─┘\n└─ '
+        self.assertEqual(expected, rendered)
diff --git a/urwid/tests/test_graphics.py b/urwid/tests/test_graphics.py
index f731208..1ae1f98 100644
--- a/urwid/tests/test_graphics.py
+++ b/urwid/tests/test_graphics.py
@@ -7,6 +7,13 @@ from urwid import graphics
 
 
 class LineBoxTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def border(self, tl, t, tr, l, r, bl, b, br):
         return [b''.join([tl, t, tr]),
                 b''.join([l, b" ", r]),
@@ -14,7 +21,6 @@ class LineBoxTest(unittest.TestCase):
 
     def test_linebox_pack(self):
         # Bug #346 'pack' Padding does not run with LineBox
-        urwid.set_encoding("utf-8")
         t = urwid.Text("AAA\nCCC\nDDD")
         size = t.pack()
         l = urwid.LineBox(t)
@@ -23,7 +29,6 @@ class LineBoxTest(unittest.TestCase):
         self.assertEqual(l.pack()[1], size[1] + 2)
 
     def test_linebox_border(self):
-        urwid.set_encoding("utf-8")
         t = urwid.Text("")
 
         l = urwid.LineBox(t).render((3,)).text
@@ -87,8 +92,14 @@ class BarGraphTest(unittest.TestCase):
              (1,[(3,3)]) ] )
 
 class SmoothBarGraphTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def sbgtest(self, desc, data, top, exp ):
-        urwid.set_encoding('utf-8')
         g = urwid.BarGraph( ['black','red','blue'],
                 None, {(1,0):'red/black', (2,1):'blue/red'})
         g.set_data( data, top )
diff --git a/urwid/tests/test_text_layout.py b/urwid/tests/test_text_layout.py
index c87d12c..95cba1c 100644
--- a/urwid/tests/test_text_layout.py
+++ b/urwid/tests/test_text_layout.py
@@ -1,11 +1,24 @@
 from __future__ import annotations
 
+import contextlib
 import unittest
+from collections.abc import Generator
 
 import urwid
 from urwid import text_layout
 
 
+@contextlib.contextmanager
+def encoding(encoding_name: str) -> Generator[None, None, None]:
+    old_encoding = 'ascii'  # Default fallback value
+    try:
+        old_encoding = urwid.util._target_encoding
+        urwid.set_encoding(encoding_name)
+        yield
+    finally:
+        urwid.set_encoding(old_encoding)
+
+
 class CalcBreaksTest:
     def cbtest(self, width, exp):
         result = text_layout.default_layout.calculate_text_segments(
@@ -33,8 +46,12 @@ class CalcBreaksCharTest(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksDBCharTest(CalcBreaksTest, unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'any'
     text = "abfgh\xA1\xA1j\xA1\xA1xskhtrvs\naltjhgsdf\xA1\xA1jahtshgf"
     # tests
@@ -68,8 +85,12 @@ class CalcBreaksWordTest2(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksDBWordTest(CalcBreaksTest, unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'space'
     text = "hel\xA1\xA1 world\nout-\xA1\xA1tre blah"
     # tests
@@ -81,9 +102,13 @@ class CalcBreaksDBWordTest(CalcBreaksTest, unittest.TestCase):
 
 
 class CalcBreaksUTF8Test(CalcBreaksTest, unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("utf-8")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'space'
     text = '\xe6\x9b\xbf\xe6\xb4\xbc\xe6\xb8\x8e\xe6\xba\x8f\xe6\xbd\xba'
     do = [
@@ -95,20 +120,28 @@ class CalcBreaksUTF8Test(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksCantDisplayTest(unittest.TestCase):
     def test(self):
-        urwid.set_encoding("euc-jp")
-        self.assertRaises(text_layout.CanNotDisplayText,
-            text_layout.default_layout.calculate_text_segments,
-            b'\xA1\xA1', 1, 'space' )
-        urwid.set_encoding("utf-8")
-        self.assertRaises(text_layout.CanNotDisplayText,
-            text_layout.default_layout.calculate_text_segments,
-            b'\xe9\xa2\x96', 1, 'space' )
+        with encoding("euc-jp"):
+            self.assertRaises(
+                text_layout.CanNotDisplayText,
+                text_layout.default_layout.calculate_text_segments,
+                b'\xA1\xA1', 1, 'space'
+            )
+        with encoding("utf-8"):
+            self.assertRaises(
+                text_layout.CanNotDisplayText,
+                text_layout.default_layout.calculate_text_segments,
+                b'\xe9\xa2\x96', 1, 'space'
+            )
 
 
 class SubsegTest(unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def st(self, seg, text, start, end, exp):
         text = text.encode('iso8859-1')
         s = urwid.LayoutSegment(seg)
@@ -151,9 +184,13 @@ class SubsegTest(unittest.TestCase):
 
 
 class CalcTranslateTest:
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("utf-8")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def test1_left(self):
         result = urwid.default_layout.layout( self.text,
             self.width, 'left', self.mode)
@@ -225,9 +262,13 @@ class CalcTranslateWordTest2(CalcTranslateTest, unittest.TestCase):
 
 
 class CalcTranslateWordTest3(CalcTranslateTest, unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding('utf-8')
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     text = b'\xe6\x9b\xbf\xe6\xb4\xbc\n\xe6\xb8\x8e\xe6\xba\x8f\xe6\xbd\xba'
     width = 10
     mode = 'space'
diff --git a/urwid/tests/test_util.py b/urwid/tests/test_util.py
index 06de8c8..d893eac 100644
--- a/urwid/tests/test_util.py
+++ b/urwid/tests/test_util.py
@@ -8,6 +8,12 @@ from urwid import util
 
 
 class CalcWidthTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def wtest(self, desc, s, exp):
         s = s.encode('iso8859-1')
         result = util.calc_width( s, 0, len(s))
@@ -29,6 +35,12 @@ class CalcWidthTest(unittest.TestCase):
 
 
 class ConvertDecSpecialTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def ctest(self, desc, s, exp, expcs):
         exp = exp.encode('iso8859-1')
         util.set_encoding('ascii')
@@ -51,8 +63,12 @@ class ConvertDecSpecialTest(unittest.TestCase):
 
 class WithinDoubleByteTest(unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def wtest(self, s, ls, pos, expected, desc):
         result = util.within_double_byte(s.encode('iso8859-1'), ls, pos)
         assert result==expected, f"{desc} got:{result!r} expected: {expected!r}"
@@ -88,6 +104,12 @@ class WithinDoubleByteTest(unittest.TestCase):
 
 
 class CalcTextPosTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def ctptest(self, text, tests):
         text = text.encode('iso8859-1')
         for s,e,p, expected in tests:
diff --git a/urwid/tests/test_widget.py b/urwid/tests/test_widget.py
index 4ea2944..9da2abb 100644
--- a/urwid/tests/test_widget.py
+++ b/urwid/tests/test_widget.py
@@ -1,10 +1,23 @@
 from __future__ import annotations
 
+import contextlib
 import unittest
+from collections.abc import Generator
 
 import urwid
 
 
+@contextlib.contextmanager
+def encoding(encoding_name: str) -> Generator[None, None, None]:
+    old_encoding = 'ascii'  # Default fallback value
+    try:
+        old_encoding = urwid.util._target_encoding
+        urwid.set_encoding(encoding_name)
+        yield
+    finally:
+        urwid.set_encoding(old_encoding)
+
+
 class TextTest(unittest.TestCase):
     def setUp(self):
         self.t = urwid.Text("I walk the\ncity in the night")
@@ -33,10 +46,10 @@ class TextTest(unittest.TestCase):
         assert got == expected, f"got: {got!r} expected: {expected!r}"
 
     def test5_encode_error(self):
-        urwid.set_encoding("ascii")
-        expected = [b"?  "]
-        got = urwid.Text('û').render((3,))._text
-        assert got == expected, f"got: {got!r} expected: {expected!r}"
+        with encoding("ascii"):
+            expected = [b"?  "]
+            got = urwid.Text('û').render((3,))._text
+            assert got == expected, f"got: {got!r} expected: {expected!r}"
 
 
 class EditTest(unittest.TestCase):
@@ -87,12 +100,12 @@ class EditTest(unittest.TestCase):
         self.ktest(self.t3,'down','down',15,"down at bottom")
 
     def test_utf8_input(self):
-        urwid.set_encoding("utf-8")
-        self.t1.set_edit_text('')
-        self.t1.keypress((12,), 'û')
-        self.assertEqual(self.t1.edit_text, 'û'.encode())
-        self.t4.keypress((12,), 'û')
-        self.assertEqual(self.t4.edit_text, 'û')
+        with encoding("utf-8"):
+            self.t1.set_edit_text('')
+            self.t1.keypress((12,), 'û')
+            self.assertEqual(self.t1.edit_text, 'û'.encode())
+            self.t4.keypress((12,), 'û')
+            self.assertEqual(self.t4.edit_text, 'û')
 
 
 class EditRenderTest(unittest.TestCase):