Fix: Merge subgroups when inserting existing rows_as_columns links

[bioinfbloke]

When merging MDV projects, insert_link() was overwriting existing
rows_as_columns links with empty subgroups, causing loss of subgroup
definitions during project merges.

Now checks if a rows_as_columns link already exists and merges the
subgroups dictionaries instead of overwriting, preserving existing
subgroups while allowing new ones to be added.

Summary by CodeRabbit

• Bug Fixes
  • Enhanced data linking behavior to merge existing data intelligently instead of overwriting blindly, preventing unintended data loss.
  • Improved property preservation logic during data linking to maintain data integrity and consistency across records.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The change enhances the insert_link method in mdvproject.py to intelligently handle rows_as_columns links by merging subgroups from new data into existing links rather than overwriting them, while preserving properties through name_column comparison.

Changes

Cohort / File(s)	Summary
Link insertion logic enhancement python/mdvtools/mdvproject.py	Modified insert_link logic to merge subgroups into existing rows_as_columns links; compares name_column to preserve/replace properties; retains prior overwrite behavior for non-matching cases or missing links; metadata updated as before

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Hop, hop, merging links with care,
Subgroups blend in columns fair,
Name by name, we match and mend,
Properties preserved, on properties depend!
No more blindly overwriting ways,
Smart merging brightens all our days! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: merging subgroups when inserting rows_as_columns links, which directly addresses the bug fix described in the PR objectives.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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🧹 Recent nitpick comments

python/mdvtools/mdvproject.py (1)

1284-1304: Redundant conditional branches and potential logic issue with subgroup merging.

Two concerns with the merge logic:

1. Lines 1295-1300 are identical in both branches - the if-else produces the same result (llink[linktype] = data) regardless of whether name_column matches. The condition is effectively dead code.

2. Subgroups are merged before the name_column check - If the intent is to overwrite (not merge) when name_column differs, the merge on lines 1291-1293 should happen after confirming name_column matches. Currently, even in the "overwrite" branch, data["subgroups"] already contains the merged result.

♻️ Suggested simplification

         # Check if link already exists and merge subgroups for rows_as_columns links
         if linktype == "rows_as_columns" and linktype in llink:
             existing_link = llink[linktype]
-            # Merge subgroups: preserve existing subgroups, add new ones from data
-            if "subgroups" in existing_link and "subgroups" in data:
-                # Merge subgroups dictionaries
-                merged_subgroups = existing_link["subgroups"].copy()
-                merged_subgroups.update(data["subgroups"])
-                data["subgroups"] = merged_subgroups
-            # Preserve other existing properties if they match
-            if existing_link.get("name_column") == data.get("name_column"):
-                # Same link configuration, merge subgroups
-                llink[linktype] = data
-            else:
-                # Different link configuration, overwrite (shouldn't happen in normal flow)
-                llink[linktype] = data
+            # Only merge subgroups if name_column matches (same link configuration)
+            if existing_link.get("name_column") == data.get("name_column"):
+                if "subgroups" in existing_link:
+                    # Preserve existing subgroups, add new ones from data
+                    merged_subgroups = existing_link["subgroups"].copy()
+                    merged_subgroups.update(data.get("subgroups", {}))
+                    data["subgroups"] = merged_subgroups
+            # Different name_column is not expected; fall through to overwrite
+            llink[linktype] = data
         else:
             # No existing link or not rows_as_columns type, overwrite as before
             llink[linktype] = data

This refactor:

• Removes redundant branches
• Only merges subgroups when name_column matches (matching the stated intent)
• Uses data.get("subgroups", {}) to handle cases where data might not have the key

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📜 Recent review details

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 076c4b2 and 9ecbe8d.

📒 Files selected for processing (1)

• python/mdvtools/mdvproject.py

🧰 Additional context used

🧠 Learnings (2)

📓 Common learnings

Learnt from: xinaesthete
Repo: Taylor-CCB-Group/MDV PR: 0
File: :0-0
Timestamp: 2025-03-17T15:08:26.492Z
Learning: The PR titled "column link" introduces the concept of dynamic column links to allow charts to reactively update based on operations in linked data sources, replacing string-based column identifiers with more robust `FieldSpec` and `ColumnQuery` systems.

📚 Learning: 2025-03-17T15:08:26.492Z

Learnt from: xinaesthete
Repo: Taylor-CCB-Group/MDV PR: 0
File: :0-0
Timestamp: 2025-03-17T15:08:26.492Z
Learning: The PR titled "column link" introduces the concept of dynamic column links to allow charts to reactively update based on operations in linked data sources, replacing string-based column identifiers with more robust `FieldSpec` and `ColumnQuery` systems.

Applied to files:

• python/mdvtools/mdvproject.py

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[xinaesthete]

I think I'd like to add a few tests to this, using some of the facilities we have for making mock-data projects.