Simplify dev_tools.notebooks.utils.rewrite_notebook (#6030)

* Simplify dev_tools.notebooks.utils.rewrite_notebook

- Do not return the OS file descriptor, it was only used
  to close the file in rewrite_notebook callers
- Return only the filename of the rewritten notebook
- Always create a temporary file, even if identical to the input notebook,
  so it can be safely removed after a test
- Clean up temporary files produced by rewrite_notebook in the tests

dev_tools/notebooks/isolated_notebook_test.py

@@ -177,7 +177,7 @@ def test_notebooks_against_released_cirq(partition, notebook_path, cloned_env):
 
     notebook_file = os.path.basename(notebook_path)
 
-    rewritten_notebook_descriptor, rewritten_notebook_path = rewrite_notebook(notebook_path)
+    rewritten_notebook_path = rewrite_notebook(notebook_path)
 
     cmd = f"""
 mkdir -p out/{notebook_rel_dir}
@@ -208,9 +208,7 @@ def test_notebooks_against_released_cirq(partition, notebook_path, cloned_env):
             f"instead of `pip install cirq` to this notebook, and exclude it from "
             f"dev_tools/notebooks/isolated_notebook_test.py."
         )
-
-    if rewritten_notebook_descriptor:
-        os.close(rewritten_notebook_descriptor)
+    os.remove(rewritten_notebook_path)
 
 
 @pytest.mark.parametrize("notebook_path", NOTEBOOKS_DEPENDING_ON_UNRELEASED_FEATURES)

dev_tools/notebooks/notebook_test.py

@@ -67,7 +67,7 @@ def test_notebooks_against_released_cirq(notebook_path):
     notebook_file = os.path.basename(notebook_path)
     notebook_rel_dir = os.path.dirname(os.path.relpath(notebook_path, "."))
     out_path = f"out/{notebook_rel_dir}/{notebook_file[:-6]}.out.ipynb"
-    rewritten_notebook_descriptor, rewritten_notebook_path = rewrite_notebook(notebook_path)
+    rewritten_notebook_path = rewrite_notebook(notebook_path)
     papermill_flags = "--no-request-save-on-cell-execute --autosave-cell-every 0"
     cmd = f"""mkdir -p out/{notebook_rel_dir}
 papermill {rewritten_notebook_path} {out_path} {papermill_flags}"""
@@ -83,6 +83,4 @@ def test_notebooks_against_released_cirq(notebook_path):
             f"notebook (in Github Actions, you can download it from the workflow artifact"
             f" 'notebook-outputs')"
         )
-
-    if rewritten_notebook_descriptor:
-        os.close(rewritten_notebook_descriptor)
+    os.remove(rewritten_notebook_path)

dev_tools/notebooks/utils.py

@@ -69,7 +69,7 @@ def rewrite_notebook(notebook_path):
 
         * Lines in this file without `->` are ignored.
 
-        * Lines in this file with `->` are split into two (if there are mulitple `->` it is an
+        * Lines in this file with `->` are split into two (if there are multiple `->` it is an
         error). The first of these is compiled into a pattern match, via `re.compile`, and
         the second is the replacement for that match.
 
@@ -82,42 +82,41 @@ def rewrite_notebook(notebook_path):
     It is the responsibility of the caller of this method to delete the new file.
 
     Returns:
-        Tuple of a file descriptor and the file path for the rewritten file.  If no `.tst` file
-        was found, then the file descriptor is None and the path is `notebook_path`.
+        The absolute path to the rewritten file in temporary directory.
+        If no `.tst` file exists the new file is a copy of the input notebook.
 
     Raises:
         AssertionError: If there are multiple `->` per line, or not all of the replacements
             are used.
     """
-    notebook_test_path = os.path.splitext(notebook_path)[0] + '.tst'
-    if not os.path.exists(notebook_test_path):
-        return None, notebook_path
-
     # Get the rewrite rules.
     patterns = []
-    with open(notebook_test_path, 'r') as f:
-        for line in f:
-            if '->' in line:
+    notebook_test_path = os.path.splitext(notebook_path)[0] + '.tst'
+    if os.path.exists(notebook_test_path):
+        with open(notebook_test_path, 'r') as f:
+            pattern_lines = (line for line in f if '->' in line)
+            for line in pattern_lines:
                 parts = line.rstrip().split('->')
                 assert len(parts) == 2, f'Replacement lines may only contain one -> but was {line}'
                 patterns.append((re.compile(parts[0]), parts[1]))
 
     used_patterns = set()
     with open(notebook_path, 'r') as original_file:
-        new_file_descriptor, new_file_path = tempfile.mkstemp(suffix='.ipynb')
-        with open(new_file_path, 'w') as new_file:
-            for line in original_file:
-                new_line = line
-                for pattern, replacement in patterns:
-                    new_line = pattern.sub(replacement, new_line)
-                    if new_line != line:
-                        used_patterns.add(pattern)
-                        break
-                new_file.write(new_line)
+        lines = original_file.readlines()
+    for i, line in enumerate(lines):
+        for pattern, replacement in patterns:
+            new_line = pattern.sub(replacement, line)
+            if new_line != line:
+                lines[i] = new_line
+                used_patterns.add(pattern)
+                break
 
     assert len(patterns) == len(used_patterns), (
         'Not all patterns where used. Patterns not used: '
         f'{set(x for x, _ in patterns) - used_patterns}'
     )
 
-    return new_file_descriptor, new_file_path
+    with tempfile.NamedTemporaryFile(mode='w', suffix='-rewrite.ipynb', delete=False) as new_file:
+        new_file.writelines(lines)
+
+    return new_file.name

dev_tools/notebooks/utils_test.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import filecmp
 import os
 import shutil
 import tempfile
@@ -37,40 +38,40 @@ def write_test_data(ipynb_txt, tst_txt):
 def test_rewrite_notebook():
     directory, ipynb_path = write_test_data('d = 5\nd = 4', 'd = 5->d = 3')
 
-    descriptor, path = dt.rewrite_notebook(ipynb_path)
+    path = dt.rewrite_notebook(ipynb_path)
 
     assert path != ipynb_path
     with open(path, 'r') as f:
         rewritten = f.read()
         assert rewritten == 'd = 3\nd = 4'
 
-    os.close(descriptor)
+    os.remove(path)
     shutil.rmtree(directory)
 
 
 def test_rewrite_notebook_multiple():
     directory, ipynb_path = write_test_data('d = 5\nd = 4', 'd = 5->d = 3\nd = 4->d = 1')
 
-    descriptor, path = dt.rewrite_notebook(ipynb_path)
+    path = dt.rewrite_notebook(ipynb_path)
 
     with open(path, 'r') as f:
         rewritten = f.read()
         assert rewritten == 'd = 3\nd = 1'
 
-    os.close(descriptor)
+    os.remove(path)
     shutil.rmtree(directory)
 
 
 def test_rewrite_notebook_ignore_non_seperator_lines():
     directory, ipynb_path = write_test_data('d = 5\nd = 4', 'd = 5->d = 3\n# comment')
 
-    descriptor, path = dt.rewrite_notebook(ipynb_path)
+    path = dt.rewrite_notebook(ipynb_path)
 
     with open(path, 'r') as f:
         rewritten = f.read()
         assert rewritten == 'd = 3\nd = 4'
 
-    os.close(descriptor)
+    os.remove(path)
     shutil.rmtree(directory)
 
 
@@ -80,11 +81,11 @@ def test_rewrite_notebook_no_tst_file():
     with open(ipynb_path, 'w') as f:
         f.write('d = 5\nd = 4')
 
-    descriptor, path = dt.rewrite_notebook(ipynb_path)
-
-    assert descriptor is None
-    assert path == ipynb_path
+    path = dt.rewrite_notebook(ipynb_path)
+    assert path != ipynb_path
+    assert filecmp.cmp(path, ipynb_path)
 
+    os.remove(path)
     shutil.rmtree(directory)