Make the formatting of a code block name extendable

Currently the user display of a code block requires a tight coupling between the caching compiler and the ultratb file, i.e., ultratb needs to know internal private variables of the caching compiler. This change makes the user-visible display of the code block name the responsibility of the caching compiler. A nice result is that the caching compiler can be overridden to have custom terminology in different systems for code blocks executed.

IPython/core/compilerop.py

@@ -116,6 +116,21 b' class CachingCompiler(codeop.Compile):'
         """
         return code_name(transformed_code, number)
 
+    def format_code_name(self, name):
+        """Return a user-friendly label and name for a code block.
+
+        Parameters
+        ----------
+        name : str
+            The name for the code block returned from get_code_name
+
+        Returns
+        -------
+        A (label, name) pair that can be used in tracebacks, or None if the default formatting should be used.
+        """
+        if name in self._filename_map:
+            return "Cell", "In[%s]" % self._filename_map[name]
+
     def cache(self, transformed_code, number=0, raw_code=None):
         """Make a name for a block of code, and cache the code.
 

IPython/core/ultratb.py

@@ -173,7 +173,7 b' def _format_traceback_lines(lines, Colors, has_colors: bool, lvals):'
 
 def _format_filename(file, ColorFilename, ColorNormal, *, lineno=None):
     """
-    Format filename lines with `In [n]` if it's the nth code cell or `File *.py` if it's a module.
+    Format filename lines with custom formatting from caching compiler or `File *.py` by default
 
     Parameters
     ----------
@@ -184,23 +184,29 b' def _format_filename(file, ColorFilename, ColorNormal, *, lineno=None):'
         ColorScheme's normal coloring to be used.
     """
     ipinst = get_ipython()
-
-    if ipinst is not None and file in ipinst.compile._filename_map:
-        file = "[%s]" % ipinst.compile._filename_map[file]
+    if (
+        ipinst is not None
+        and (data := ipinst.compile.format_code_name(file)) is not None
+    ):
+        label, name = data
         if lineno is None:
-            tpl_link = f"Cell {ColorFilename}In {{file}}{ColorNormal}"
+            tpl_link = f"{{label}} {ColorFilename}{{name}}{ColorNormal}"
         else:
-            tpl_link = f"Cell {ColorFilename}In {{file}}, line {{lineno}}{ColorNormal}"
+            tpl_link = (
+                f"{{label}} {ColorFilename}{{name}}, line {{lineno}}{ColorNormal}"
+            )
     else:
-        file = util_path.compress_user(
+        label = "File"
+        name = util_path.compress_user(
             py3compat.cast_unicode(file, util_path.fs_encoding)
         )
         if lineno is None:
-            tpl_link = f"File {ColorFilename}{{file}}{ColorNormal}"
+            tpl_link = f"{{label}} {ColorFilename}{{name}}{ColorNormal}"
         else:
-            tpl_link = f"File {ColorFilename}{{file}}:{{lineno}}{ColorNormal}"
+            # can we make this the more friendly ", line {{lineno}}", or do we need to preserve the formatting with the colon?
+            tpl_link = f"{{label}} {ColorFilename}{{name}}:{{lineno}}{ColorNormal}"
 
-    return tpl_link.format(file=file, lineno=lineno)
+    return tpl_link.format(label=label, name=name, lineno=lineno)
 
 #---------------------------------------------------------------------------
 # Module classes