Issue #21477: Idle htest: modify run; add more tests.

Patch by Saimadhav Heblikar. 2.7 version will follow.

Lib/idlelib/StackViewer.py

@@ -1,9 +1,12 @@
 import os
 import sys
 import linecache
+import re
+import tkinter as tk
 
 from idlelib.TreeWidget import TreeNode, TreeItem, ScrolledCanvas
 from idlelib.ObjectBrowser import ObjectTreeItem, make_objecttreeitem
+from idlelib.PyShell import PyShellFileList
 
 def StackBrowser(root, flist=None, tb=None, top=None):
     if top is None:
@@ -120,3 +123,30 @@ class VariablesTreeItem(ObjectTreeItem):
             item = make_objecttreeitem(key + " =", value, setfunction)
             sublist.append(item)
         return sublist
+
+def _stack_viewer(parent):
+    root = tk.Tk()
+    root.title("Test StackViewer")
+    width, height, x, y = list(map(int, re.split('[x+]', parent.geometry())))
+    root.geometry("+%d+%d"%(x, y + 150))
+    flist = PyShellFileList(root)
+    try: # to obtain a traceback object
+        a
+    except:
+        exc_type, exc_value, exc_tb = sys.exc_info()
+
+    # inject stack trace to sys
+    sys.last_type = exc_type
+    sys.last_value = exc_value
+    sys.last_traceback = exc_tb
+
+    StackBrowser(root, flist=flist, top=root, tb=exc_tb)
+
+    # restore sys to original state
+    del sys.last_type
+    del sys.last_value
+    del sys.last_traceback
+
+if __name__ == '__main__':
+    from idlelib.idle_test.htest import run
+    run(_stack_viewer)