Mark source parameter of publish_display_data.

Closes  #13365

IPython/core/display_functions.py

@@ -8,6 +8,7
 from binascii import b2a_hex
 import os
 import sys
+import warnings
 
 __all__ = ['display', 'clear_output', 'publish_display_data', 'update_display', 'DisplayHandle']
 
@@ -33,9 +34,17 def _merge(d1, d2):
 # Main functions
 #-----------------------------------------------------------------------------
 
+class _Sentinel:
+    def __repr__(self):
+        return "<deprecated>"
+
+
+_sentinel = _Sentinel()
 
 # use * to indicate transient is keyword-only
-def publish_display_data(data, metadata=None, source=None, *, transient=None, **kwargs):
+def publish_display_data(
+    data, metadata=None, source=_sentinel, *, transient=None, **kwargs
+):
     """Publish data and metadata to all frontends.
 
     See the ``display_data`` message in the messaging documentation for
@@ -65,6 +74,14 def publish_display_data(data, metadata=None, source=None, *, transient=None, **
     """
     from IPython.core.interactiveshell import InteractiveShell
 
+    if source is not _sentinel:
+        warnings.warn(
+            "The `source` parameter emit a  deprecation warning since"
+            " IPython 8.0, it had no effects for a long time and will "
+            " be removed in future versions.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
     display_pub = InteractiveShell.instance().display_pub
 
     # only pass transient if supplied,

IPython/terminal/tests/test_interactivshell.py

@@ -191,13 +191,14 class InteractiveShellTestCase(unittest.TestCase):
         class Test2(Test):
             def _ipython_display_(self):
                 from IPython.display import display, HTML
-                display(HTML('<custom>'))
+
+                display(HTML("<custom>"))
 
         # verify that mimehandlers are called
         called = False
 
         def handler(data, metadata):
-            print('Handler called')
+            print("Handler called")
             nonlocal called
             called = True
 
@@ -205,12 +206,11 class InteractiveShellTestCase(unittest.TestCase):
         ip.display_formatter.formatters["text/html"].enabled = True
         ip.mime_renderers["text/html"] = handler
 
-
         obj = Test()
         display(obj)
 
         assert called == True
-        
+
 
 def syntax_error_transformer(lines):
     """Transformer that throws SyntaxError if 'syntaxerror' is in the code."""