Auto-select the sole coordinate system

[xinaesthete]

Harvested from the larger points-loading branch as an isolated, low-risk change.

When a SpatialData object exposes exactly one coordinate system, select it by default instead of leaving the picker on "Select a coordinate system". Multi-system datasets still require an explicit choice (the previous behaviour eagerly picked the first of several, which this also removes).

• Single file: packages/vis/src/SpatialCanvas/index.tsx
• Patch changeset for @spatialdata/vis included.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Coordinate system selection now behaves more predictably when loading spatial data.
  • If only one coordinate system is available, it is selected automatically.
  • When multiple coordinate systems are available, the picker no longer preselects one by default.
  • Existing selections are preserved when still valid after a refresh or reset.

[coderabbitai]

📝 Walkthrough

Walkthrough

Consolidates two separate effects in SpatialCanvasInner into a single useEffect that resets the store and computes the active coordinate system, defaulting only when exactly one coordinate system is available; adds a changeset documenting this behavior change.

Changes

Coordinate System Selection Fix

Layer / File(s)	Summary
Unified reset and selection logic packages/vis/src/SpatialCanvas/index.tsx	Merges reset and coordinate-system selection into one effect; retains current selection if still valid, defaults to the sole available system only when exactly one exists, otherwise null.
Changelog entry .changeset/default-coordinate-system-selection.md	Adds a patch changeset for @spatialdata/vis documenting the updated default-selection behavior.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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: automatically selecting the only available coordinate system.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch harvest/default-cs-selection

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[coderabbitai]

🧹 Nitpick comments (2)

packages/vis/src/SpatialCanvas/index.tsx (2)

460-471: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Effect re-triggers itself on auto-select, causing a redundant actions.reset().

coordinateSystem is both read and written by this effect. When it starts falsy and coordinateSystems.length === 1, actions.setCoordinateSystem(coordinateSystems[0]) changes the store's coordinateSystem to a genuinely new value, which re-runs this same effect (since coordinateSystem is a dependency) and calls actions.reset() a second time. Previously the "preserve current selection" branch called setCoordinateSystem with the same value it already held, so it never changed the subscribed slice and never re-triggered itself — the new defaulting branch is the first path that can do so.

React 18's automatic batching means both set() calls inside one effect run get batched into a single commit, so there's no visible flicker, but the effect body (including reset(), which also clears layers/layerOrder/selectedLayerId/viewState) still executes twice for this transition. This is currently harmless at mount, but is a fragile coupling if more logic is ever added to reset().

Consider decoupling "is the current selection still valid" (read via a ref, not a dependency) from "did the available coordinateSystems change" (the real trigger for reset), so the effect doesn't re-run because of its own write.

♻️ Illustrative refactor (verify against desired "reset on manual switch" semantics)

+  const coordinateSystemRef = useRef(coordinateSystem);
+  coordinateSystemRef.current = coordinateSystem;
+
   useEffect(() => {
     actions.reset();
-    const nextCoordinateSystem =
-      coordinateSystem && coordinateSystems.includes(coordinateSystem)
-        ? coordinateSystem
-        : coordinateSystems.length === 1
-          ? coordinateSystems[0]
-          : null;
+    const current = coordinateSystemRef.current;
+    const nextCoordinateSystem =
+      current && coordinateSystems.includes(current)
+        ? current
+        : coordinateSystems.length === 1
+          ? coordinateSystems[0]
+          : null;
     if (nextCoordinateSystem) {
       actions.setCoordinateSystem(nextCoordinateSystem);
     }
-  }, [coordinateSystem, coordinateSystems, actions]);
+  }, [coordinateSystems, actions]);

Note: this changes when reset() fires — confirm whether manual coordinate-system switches (via handleCSChange) are still meant to clear layers/selection before adopting this.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/vis/src/SpatialCanvas/index.tsx` around lines 460 - 471, The
useEffect in SpatialCanvas is re-triggering itself because it both reads and
writes coordinateSystem, causing a redundant actions.reset() when auto-selecting
the single available coordinate system. Decouple the reset trigger from the
selected value by basing the effect on coordinateSystems changes only, and use a
ref or equivalent to check whether the current coordinateSystem is still valid
before calling actions.setCoordinateSystem. Keep the reset/set logic in
SpatialCanvas and ensure handleCSChange semantics still behave as intended.

---

460-471: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add test coverage for the new selection matrix.

This effect now encodes several distinct, user-facing branches (0 systems, exactly 1, N with valid current selection, N with stale/invalid current selection). Given the PR explicitly fixes a prior UX bug here, a small unit/integration test around SpatialCanvasInner's coordinate-system selection would guard against regressions.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/vis/src/SpatialCanvas/index.tsx` around lines 460 - 471, Add test
coverage around SpatialCanvasInner’s coordinate-system selection effect, since
it now has distinct branches for no available systems, exactly one system, a
valid current selection, and a stale/invalid selection. Create focused
unit/integration tests that exercise the useEffect logic in SpatialCanvasInner
and verify actions.reset and actions.setCoordinateSystem are called
appropriately for each case, so the new selection matrix is protected from
regressions.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@packages/vis/src/SpatialCanvas/index.tsx`:
- Around line 460-471: The useEffect in SpatialCanvas is re-triggering itself
because it both reads and writes coordinateSystem, causing a redundant
actions.reset() when auto-selecting the single available coordinate system.
Decouple the reset trigger from the selected value by basing the effect on
coordinateSystems changes only, and use a ref or equivalent to check whether the
current coordinateSystem is still valid before calling
actions.setCoordinateSystem. Keep the reset/set logic in SpatialCanvas and
ensure handleCSChange semantics still behave as intended.
- Around line 460-471: Add test coverage around SpatialCanvasInner’s
coordinate-system selection effect, since it now has distinct branches for no
available systems, exactly one system, a valid current selection, and a
stale/invalid selection. Create focused unit/integration tests that exercise the
useEffect logic in SpatialCanvasInner and verify actions.reset and
actions.setCoordinateSystem are called appropriately for each case, so the new
selection matrix is protected from regressions.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d2a4fffc-bf4e-4e8f-9471-964816b1ca10

📥 Commits

Reviewing files that changed from the base of the PR and between f973983 and 6b91310.

📒 Files selected for processing (2)

• .changeset/default-coordinate-system-selection.md
• packages/vis/src/SpatialCanvas/index.tsx