Revert unintended effects of #1966 (#1974)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Steven Silvester <[email protected]>

nbconvert/nbconvertapp.py

@@ -218,7 +218,7 @@ def _classes_default(self):
     output_base = Unicode(
         "{notebook_name}",
         help="""Overwrite base name use for output files.
-            Supports pattern replacements '{notebook_name}' and '{notebook_filename}'.
+            Supports pattern replacements '{notebook_name}'.
             """,
     ).tag(config=True)
 
@@ -420,9 +420,7 @@ def _notebook_filename_to_name(self, notebook_filename):
         """
         basename = os.path.basename(notebook_filename)
         notebook_name = basename[: basename.rfind(".")]
-        notebook_name = self.output_base.format(
-            notebook_name=notebook_name, notebook_filename=notebook_filename
-        )
+        notebook_name = self.output_base.format(notebook_name=notebook_name)
 
         return notebook_name
 
@@ -513,7 +511,7 @@ def write_single_notebook(self, output, resources):
             raise KeyError(msg)
 
         notebook_name = resources["unique_key"]
-        if self.use_output_suffix:
+        if self.use_output_suffix and self.output_base == "{notebook_name}":
             notebook_name += resources.get("output_suffix", "")
 
         write_results = self.writer.write(output, resources, notebook_name=notebook_name)
@@ -585,18 +583,6 @@ def convert_notebooks(self):
             if ext == self.exporter.file_extension:
                 self.output_base = base
 
-        # Validate that output_base does not cause us to overwrite already generated
-        # files
-        notebook_names = [self._notebook_filename_to_name(fn) for fn in self.notebooks]
-        if len(notebook_names) != len(set(notebook_names)):
-            msg = (
-                "Conversion would override an already generated output. "
-                "This is probably due to --output or output_base configuration "
-                "leading to non-unique output names. "
-                f"Output notebook names were: {notebook_names}"
-            )
-            raise ValueError(msg)
-
         # convert each notebook
         if not self.from_stdin:
             for notebook_filename in self.notebooks:

nbconvert/tests/test_nbconvertapp.py

@@ -654,16 +654,31 @@ def test_output_base(self):
             for nbn in notebook_names:
                 assert os.path.isfile(f"{nbn}.md")
 
-        with pytest.raises(OSError), self.create_temp_cwd([x + ".ipynb" for x in notebook_names]):
-            self.nbconvert("*.ipynb --output notebook_test_name --to markdown")
-
         # Test single output with static output name
-        with self.create_temp_cwd([notebook_names[0] + ".ipynb"]):
-            self.nbconvert("*.ipynb --output notebook_test_name --to markdown")
+        nbname = notebook_names[0]
+        with self.create_temp_cwd([nbname + ".ipynb"]):
+            self.nbconvert(f"{nbname}.ipynb --output notebook_test_name --to markdown")
             assert os.path.isfile("notebook_test_name.md")
 
+            self.nbconvert(f"{nbname}.ipynb --to notebook")
+            assert os.path.isfile("notebook1.nbconvert.ipynb")
+
+            self.nbconvert(f"{nbname}.ipynb --to notebook --output out.ipynb")
+            assert os.path.isfile("out.ipynb")
+
         # Test double extension fix
         with self.create_temp_cwd([notebook_names[0] + ".ipynb"]):
             self.nbconvert("*.ipynb --output notebook_test_name.md --to markdown")
             assert os.path.isfile("notebook_test_name.md")
             assert not os.path.isfile("notebook_test_name.md.md")
+
+    def test_same_filename_different_dir(self):
+        """
+        Check if files with same name in different directories pose a problem
+        """
+        with self.create_temp_cwd() as temp_wd:
+            self.copy_files_to(["notebook1.ipynb"], temp_wd + "/dir1")
+            self.copy_files_to(["notebook1.ipynb"], temp_wd + "/dir2")
+            self.nbconvert("dir1/notebook1.ipynb dir2/notebook1.ipynb --to markdown")
+            assert os.path.isfile("dir1/notebook1.md")
+            assert os.path.isfile("dir2/notebook1.md")