[google_maps_flutter_platform_interface] Add editable polyline and polygon API

[lume-code]

Updated: Per review feedback, this PR has been split along the federated plugin so the platform interface lands first (contributing guidelines). This PR is now scoped to the platform interface only. The implementation follows in:

• Web: [google_maps_flutter_web] Add editable polyline and polygon support #11919
• App-facing google_maps_flutter: [google_maps_flutter] Add editable polyline and polygon support (web) #11920

Adds the platform-interface API surface for editable polylines and polygons. This has been requested since November 2020 (flutter/flutter#71248).

Changes — google_maps_flutter_platform_interface (2.15.0 → 2.16.0)

• Adds editable (bool, default false) and onEdited (callback) fields to Polyline and Polygon.
• Adds PolylineEditEvent and PolygonEditEvent map event types.
• Adds onPolylineEdited and onPolygonEdited streams to GoogleMapsFlutterPlatform (default UnimplementedError).

All additions are non-breaking: the new constructor parameters are defaulted/optional, and the new platform methods have default implementations.

Editing is implemented for web only (see #11919); the property is silently ignored on Android and iOS.

Fixes flutter/flutter#71248

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• All existing and new tests are passing.

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[gemini-code-assist]

Code Review

This pull request introduces support for user-editable Polygons and Polylines on the web platform by adding an editable property and an onEdited callback to the respective classes. The implementation includes new event types in the platform interface and logic in the web plugin to listen for path changes via the Google Maps JavaScript API. Review feedback highlights that the current Polygon implementation fails to include hole data in the edit events and callbacks. Furthermore, the web controllers only set up edit listeners during construction, which prevents the functionality from working if the editable property is enabled after the object is created.

[stuartmorgan-g]

20 in platform_interface, 4 in main package

This PR has substantive changes to three packages; so can't have comprehensive test coverage without adding tests in all three.

[stuartmorgan-g]

From triage: @lume-code Are you planning on adding the necessary test coverage for this to move forward?

[mdebbar]

From web triage: @lume-code are you still planning to move forward with this PR?

[lume-code]

@mdebbar yes, still moving forward — sorry for the delay. Web test coverage is now in (commit 81bf57a), and the branch has been rebased onto current main.

The new tests live under packages/google_maps_flutter/google_maps_flutter_web/example/integration_test/ and add 18 cases across shape_test.dart (controller-level) and shapes_test.dart (controllers + stream-level). They cover:

• editable is forwarded to the underlying gmaps.Polyline / gmaps.Polygon option
• onEdited fires on MVCArray setAt / insertAt / removeAt for both controllers
• PolygonEditEvent.holes is populated, and edits to a hole path also fire the event (regression for the missing-holes review comment)
• No event is emitted when the shape is not editable
• changePolylines / changePolygons rewires the edit listeners when editable is toggled false → true (regression for the "listener not re-subscribed on update" review comment)
• remove() cancels the edit subscriptions

All tests pass locally. Ready for another look whenever you have a moment.

[mdebbar]

Changes look good to me!

I think this PR now needs to be split so the platform interface package lands first?

[lume-code]

Thanks for the review! As suggested, I've split this along the federated plugin so the platform interface can land and publish first.

This PR (#11492) is now scoped to google_maps_flutter_platform_interface only. The follow-ups, stacked in dependency order, are open as drafts and will be ready once the package(s) they depend on publish:

1. [google_maps_flutter_platform_interface] Add editable polyline and polygon API #11492 — google_maps_flutter_platform_interface (2.16.0) ← lands & publishes first
2. [google_maps_flutter_web] Add editable polyline and polygon support #11919 — google_maps_flutter_web (0.7.0) — depends on the published interface
3. [google_maps_flutter] Add editable polyline and polygon support (web) #11920 — google_maps_flutter (2.18.0) — depends on the published interface + web