Add a test to document when pygment lexers appear in MyST Markdown (#778

)

* New test to document when the ipython3 lexer appears in Myst MD files

* Version 1.11.2

docs/CHANGELOG.md

@@ -1,7 +1,7 @@
 Jupytext ChangeLog
 ==================
 
-1.11.2 (2021-05-??)
+1.11.2 (2021-05-02)
 -------------------
 
 **Changed**
@@ -14,6 +14,9 @@ Jupytext ChangeLog
   cell metadata like `lines_to_next_cell` from the text file rather than ipynb ([#761](https://github.com/mwouts/jupytext/issues/761))
 - The timestamp of the source file is not updated any more when the destination file is not in the pair ([#765](https://github.com/mwouts/jupytext/issues/765), [#767](https://github.com/mwouts/jupytext/issues/767))
 
+**Added**
+- A new test documents when the `ipython3` pygment lexer appears in MyST Markdown files ([#759](https://github.com/mwouts/jupytext/issues/759))
+
 
 1.11.1 (2021-03-26)
 -------------------

jupytext/version.py

@@ -1,3 +1,3 @@
 """Jupytext's version number"""
 
-__version__ = "1.11.1+dev"
+__version__ = "1.11.2"

tests/test_ipynb_to_myst.py

@@ -1,3 +1,4 @@
+import json
 import unittest.mock as mock
 from textwrap import dedent
 
@@ -7,6 +8,7 @@
 
 import jupytext
 from jupytext.cli import jupytext as jupytext_cli
+from jupytext.compare import compare
 from jupytext.formats import (
     JupytextFormatError,
     get_format_implementation,
@@ -193,3 +195,58 @@ def test_meaningfull_error_open_myst_missing(tmpdir):
 
     with pytest.raises(HTTPError, match=PLEASE_INSTALL_MYST):
         cm.get("notebook.md")
+
+
+@requires_myst
+@pytest.mark.parametrize("language_info", ["none", "std", "no_pygments_lexer"])
+def test_myst_representation_same_cli_or_contents_manager(
+    tmpdir, cwd_tmpdir, notebook_with_outputs, language_info
+):
+    """This test gives some information on #759. As of Jupytext 1.11.1, in the MyST Markdown format,
+    the code cells have an ipython3 lexer when the notebook "language_info" metadata has "ipython3"
+    as the pygments_lexer. This information comes from the kernel and ATM it is not clear how the user
+    can choose to include it or not in the md file."""
+
+    nb = notebook_with_outputs
+    if language_info != "none":
+        nb["metadata"]["language_info"] = {
+            "codemirror_mode": {"name": "ipython", "version": 3},
+            "file_extension": ".py",
+            "mimetype": "text/x-python",
+            "name": "python",
+            "nbconvert_exporter": "python",
+            "pygments_lexer": "ipython3",
+            "version": "3.7.3",
+        }
+    if language_info == "no_pygments_lexer":
+        del nb["metadata"]["language_info"]["pygments_lexer"]
+
+    # Writing the notebook with the Python API
+    text_api = jupytext.writes(nb, fmt="md:myst")
+
+    # How do code cells look like?
+    code_cells = set(
+        line for line in text_api.splitlines() if line.startswith("```{code-cell")
+    )
+
+    if language_info == "std":
+        assert code_cells == {"```{code-cell} ipython3"}
+    else:
+        assert code_cells == {"```{code-cell}"}
+
+    # We get the same file with the command line jupytext
+    tmpdir.mkdir("cli").join("notebook.ipynb").write(json.dumps(nb))
+    jupytext_cli(["--to", "md:myst", "cli/notebook.ipynb"])
+    text_cli = tmpdir.join("cli").join("notebook.md").read()
+
+    compare(text_cli, text_api)
+
+    # Or with the contents manager
+    cm = jupytext.TextFileContentsManager()
+    cm.formats = "ipynb,md:myst"
+    cm.root_dir = str(tmpdir.mkdir("contents_manager"))
+
+    cm.save(model=dict(content=nb, type="notebook"), path="notebook.ipynb")
+    text_cm = tmpdir.join("contents_manager").join("notebook.md").read()
+
+    compare(text_cm, text_api)