Using ruamel for round trip yaml file parsing

Author: jc

pyproject.toml

@@ -28,6 +28,7 @@ dependencies = [
     "psycopg2-binary>=2.9.11",
     "temporalio>=1.18.1",
     "requests>=2.32.5",
+    "ruamel.yaml>=0.18.6",
 ]
 
 [build-system]

src/cli/deployment/helm_deployer/config_sync.py

@@ -3,30 +3,17 @@
 This module handles copying configuration files to the Helm staging area
 and synchronizing settings between the application config and Helm values.
 
-Note on YAML editing:
-    This module uses regex-based line editing to preserve comments and structure
-    in values.yaml. If more complex YAML manipulation is needed in the future,
-    consider using `ruamel.yaml` instead of `pyyaml`. ruamel.yaml preserves
-    comments, ordering, and formatting when round-tripping YAML files:
-
-        from ruamel.yaml import YAML
-        yaml = YAML()
-        yaml.preserve_quotes = True
-        with open(path) as f:
-            data = yaml.load(f)
-        # modify data...
-        with open(path, 'w') as f:
-            yaml.dump(data, f)
+Uses ruamel.yaml for YAML editing to preserve comments, ordering, and formatting
+when round-tripping YAML files.
 """
 
 from __future__ import annotations
 
-import re
 import shutil
 from pathlib import Path
 from typing import TYPE_CHECKING
 
-import yaml  # type: ignore[import-untyped]
+from ruamel.yaml import YAML
 
 from src.app.runtime.config.config_loader import load_config
 
@@ -100,7 +87,7 @@ def _compute_config_changes(
     ) -> list[str]:
         """Compare and update values.yaml with config.yaml settings.
 
-        Uses line-based editing to preserve comments and formatting in values.yaml.
+        Uses ruamel.yaml to preserve comments and formatting in values.yaml.
 
         Args:
             config_path: Path to config.yaml
@@ -112,78 +99,44 @@ def _compute_config_changes(
         config_raw = load_config(config_path, processed=False)
         config_data = config_raw if isinstance(config_raw, dict) else {}
 
+        # Set up ruamel.yaml for round-trip (comment-preserving) mode
+        yaml = YAML()
+        yaml.preserve_quotes = True
+
         # Read values.yaml for comparison (to detect what needs changing)
         with open(values_path) as f:
-            values_data = yaml.safe_load(f)
+            values_data = yaml.load(f)
 
         changes = []
-        updates: dict[str, tuple[bool, bool]] = {}  # key -> (old_val, new_val)
+        modified = False
 
         # Check redis.enabled
         if redis_config := config_data.get("config", {}).get("redis"):
             if "redis" in values_data:
                 old_val = values_data["redis"].get("enabled", True)
                 new_val = redis_config.get("enabled", True)
                 if old_val != new_val:
-                    updates["redis"] = (old_val, new_val)
+                    values_data["redis"]["enabled"] = new_val
                     changes.append(f"redis.enabled: {old_val} → {new_val}")
+                    modified = True
 
         # Check temporal.enabled
         if temporal_config := config_data.get("config", {}).get("temporal"):
             if "temporal" in values_data:
                 old_val = values_data["temporal"].get("enabled", True)
                 new_val = temporal_config.get("enabled", True)
                 if old_val != new_val:
-                    updates["temporal"] = (old_val, new_val)
+                    values_data["temporal"]["enabled"] = new_val
                     changes.append(f"temporal.enabled: {old_val} → {new_val}")
+                    modified = True
 
-        if updates:
-            self._update_values_preserving_format(values_path, updates)
+        # Write back with preserved formatting if any changes were made
+        if modified:
+            with open(values_path, "w") as f:
+                yaml.dump(values_data, f)
 
         return changes
 
-    def _update_values_preserving_format(
-        self,
-        values_path: Path,
-        updates: dict[str, tuple[bool, bool]],
-    ) -> None:
-        """Update values.yaml while preserving comments and formatting.
-
-        Uses line-based editing to find and update specific values without
-        rewriting the entire file.
-
-        Args:
-            values_path: Path to values.yaml
-            updates: Dict of section_name -> (old_value, new_value) to update
-        """
-        with open(values_path) as f:
-            lines = f.readlines()
-
-        current_section: str | None = None
-        modified_lines = []
-
-        for line in lines:
-            # Detect top-level section (no leading whitespace, ends with :)
-            stripped = line.rstrip()
-            if stripped and not line[0].isspace() and stripped.endswith(":"):
-                # Extract section name (e.g., "redis:" -> "redis")
-                current_section = stripped[:-1].split("#")[0].strip()
-
-            # Check if this line is an 'enabled:' setting in a section we want to update
-            if current_section in updates:
-                # Match lines like "  enabled: true" or "  enabled: false"
-                match = re.match(r"^(\s+enabled:\s*)(true|false)(.*)$", line)
-                if match:
-                    indent, old_bool, rest = match.groups()
-                    _, new_val = updates[current_section]
-                    new_bool = "true" if new_val else "false"
-                    line = f"{indent}{new_bool}{rest}\n"
-
-            modified_lines.append(line)
-
-        with open(values_path, "w") as f:
-            f.writelines(modified_lines)
-
     def copy_config_files(self, progress_factory: type[Progress]) -> None:
         """Copy configuration files to Helm staging area.