fix comment exploding autoconfig

data/test_config/config_with_comment_between_suggestions.yml

@@ -0,0 +1,31 @@
+language: en
+pipeline:
+# # No configuration for the NLU pipeline was provided. The following default pipeline was used to train your model.
+# # If you'd like to customize it, uncomment and adjust the pipeline.
+# # See https://rasa.com/docs/rasa/tuning-your-model for more information.
+#   - name: WhitespaceTokenizer
+#   - name: RegexFeaturizer
+#   - name: LexicalSyntacticFeaturizer
+#   - name: CountVectorsFeaturizer
+#   - name: CountVectorsFeaturizer
+#     analyzer: char_wb
+#     min_ngram: 1
+#     max_ngram: 4
+#   - name: DIETClassifier
+#     epochs: 100
+#   - name: EntitySynonymMapper
+#   - name: ResponseSelector
+#     epochs: 100
+#   - name: FallbackClassifier
+#     threshold: 0.3
+#     ambiguity_threshold: 0.1
+# some other comment in here
+policies:
+# # No configuration for policies was provided. The following default policies were used to train your model.
+# # If you'd like to customize them, uncomment and adjust the policies.
+# # See https://rasa.com/docs/rasa/policies for more information.
+#   - name: MemoizationPolicy
+#   - name: TEDPolicy
+#     max_history: 5
+#     epochs: 100
+#   - name: RulePolicy

rasa/shared/importers/autoconfig.py

@@ -2,6 +2,7 @@
 import logging
 import os
 from enum import Enum
+from pathlib import Path
 from typing import Text, Dict, Any, List, Set, Optional
 
 import rasa.shared.constants
@@ -165,14 +166,14 @@ def _dump_config(
 
     autoconfig_lines = _get_commented_out_autoconfig_lines(config, auto_configured_keys)
 
-    with open(
-        config_file_path, "r+", encoding=rasa.shared.utils.io.DEFAULT_ENCODING
-    ) as f:
-        lines = f.readlines()
-        updated_lines = _get_lines_including_autoconfig(lines, autoconfig_lines)
-        f.seek(0)
-        for line in updated_lines:
-            f.write(line)
+    current_config_content = rasa.shared.utils.io.read_file(config_file_path)
+    current_config_lines = current_config_content.splitlines(keepends=True)
+
+    updated_lines = _get_lines_including_autoconfig(
+        current_config_lines, autoconfig_lines
+    )
+
+    rasa.shared.utils.io.write_text_file("".join(updated_lines), config_file_path)
 
     auto_configured_keys = rasa.shared.utils.common.transform_collection_to_sentence(
         auto_configured_keys

tests/shared/importers/test_autoconfig.py

@@ -205,3 +205,19 @@ def test_get_configuration_for_different_training_types(
     expected = rasa.shared.utils.io.read_file(str(CONFIG_FOLDER / expected_file))
 
     assert actual == expected
+
+
+def test_comment_causing_invalid_autoconfig(tmp_path: Path):
+    """Regression test for https://github.com/RasaHQ/rasa/issues/6948."""
+
+    config_file = tmp_path / "config.yml"
+    shutil.copyfile(
+        str(CONFIG_FOLDER / "config_with_comment_between_suggestions.yml"), config_file
+    )
+
+    _ = autoconfig.get_configuration(str(config_file))
+
+    # This should not throw
+    dumped = rasa.shared.utils.io.read_yaml_file(config_file)
+
+    assert dumped