Populate notebook metadata when exporting with %notebook magic (ipython#14955)

Fixes ipython#14954

Author: krassowski

IPython/core/magics/basic.py

@@ -4,6 +4,7 @@
 from logging import error
 import io
 import os
+import platform
 from pprint import pformat
 import sys
 from warnings import warn
@@ -603,10 +604,44 @@ def notebook(self, s):
                 )
             cells.append(cell)
 
-        nb = v4.new_notebook(cells=cells)
+        kernel_language_info = self._get_kernel_language_info()
+
+        nb = v4.new_notebook(
+            cells=cells,
+            metadata={
+                "kernelspec": {
+                    "display_name": "Python 3 (ipykernel)",
+                    "language": "python",
+                    "name": "python3",
+                },
+                "language_info": kernel_language_info
+                or {
+                    "codemirror_mode": {
+                        "name": "ipython",
+                        "version": sys.version_info[0],
+                    },
+                    "file_extension": ".py",
+                    "mimetype": "text/x-python",
+                    "name": "python",
+                    "nbconvert_exporter": "python",
+                    "pygments_lexer": "ipython3",
+                    "version": platform.python_version(),
+                },
+            },
+        )
         with io.open(outfname, "w", encoding="utf-8") as f:
             write(nb, f, version=4)
 
+    def _get_kernel_language_info(self) -> dict | None:
+        """Get language info from kernel, useful when used in Jupyter Console where kernels exist."""
+        if not hasattr(self.shell, "kernel"):
+            return
+        if not hasattr(self.shell.kernel, "language_info"):
+            return
+        if not isinstance(self.shell.kernel.language_info, dict):
+            return
+        return self.shell.kernel.language_info
+
 @magics_class
 class AsyncMagics(BasicMagics):
 

tests/test_magic.py

@@ -3,7 +3,9 @@
 
 import gc
 import io
+import json
 import os
+import platform
 import re
 import shlex
 import signal
@@ -962,6 +964,17 @@ def test_notebook_export_json():
     with TemporaryDirectory() as td:
         outfile = os.path.join(td, "nb.ipynb")
         _ip.run_line_magic("notebook", "%s" % outfile)
+        with open(outfile) as f:
+            exported = json.load(f)
+
+    # check metadata
+    language_info = exported["metadata"]["language_info"]
+    assert language_info["name"] == "python"
+    assert language_info["file_extension"] == ".py"
+    assert language_info["version"] == platform.python_version()
+
+    kernelspec = exported["metadata"]["kernelspec"]
+    assert kernelspec["language"] == "python"
 
 
 def test_notebook_export_json_with_output():