fix: AshGeo.GeoJson.cast_stored handles GeoJSON maps

[matt-beanland]

Problem

AshGeo.GeoJson.cast_input/2 decodes GeoJSON-shaped maps (atom- or string-keyed) via Geo.JSON.decode/1:

def cast_input(%{type: _} = value, constraints) do
  with {:ok, value} <- Jason.encode(value),
       {:ok, value} <- Jason.decode(value),
       {:ok, value} <- Geo.JSON.decode(value) do
    {:ok, value}
  else
    _ -> :error
  end
end

def cast_input(value, constraints) when is_map(value) and not is_struct(value) do
  case Geo.JSON.decode(value) do
    {:ok, _} = res -> res
    _ -> :error
  end
end

But cast_stored/2 is not overridden in AshGeo.GeoJson.Use, so it falls through to the base AshGeo.Geometry implementation, which only accepts %Geo.*{} structs and nil:

def cast_stored(%struct{} = value, _) when is_geo(struct), do: {:ok, value}
def cast_stored(nil, _), do: {:ok, nil}
def cast_stored(_, _), do: :error   # <- maps land here

This breaks any data layer that stores GeoJSON as a map/JSON value and hands it back as a map on read. The case that bit me: an AshGeo.GeoJson field nested inside an Ash.TypedStruct. When the TypedStruct walks its fields on cast_stored, the geo field is handed the decoded GeoJSON map and AshGeo.GeoJson.cast_stored returns :error, failing the whole load — even though cast_input would have accepted the identical map.

Fix

Add map-handling cast_stored/2 clauses to AshGeo.GeoJson.Use mirroring the existing cast_input/2 clauses — same Jason round-trip for atom-keyed maps, same Geo.JSON.decode for string-keyed maps, falling through to super/2 for structs/nil/binaries.

Tests

Adds cast_stored cases for atom-keyed map, string-keyed map, and nil, alongside the existing Geo-struct case. Verified locally that Geo struct / nil / binary-rejection behaviour is unchanged.

---

Discovered while adopting AshGeo as the spatial type surface for ash_neo4j (a Neo4j Ash.DataLayer), which stores geometries as RFC 7946 GeoJSON. Pairs with #13 (the bare-atom geo_types formatter crash). Happy to adjust to fit your preferences.

Summary by CodeRabbit

• Bug Fixes

  • Fixed improper handling of GeoJSON deserialization from storage when GeoJSON values are nested within other typed data structures, ensuring they deserialize correctly.

• Tests

  • Added test coverage validating GeoJSON deserialization from stored data with various input formats.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 785fded5-5130-4bd7-97e8-accd963c9f43

📥 Commits

Reviewing files that changed from the base of the PR and between c002217 and 30058da.

📒 Files selected for processing (2)

• lib/ash_geo/geo_json.ex
• test/ash_geo_test.exs

---

📝 Walkthrough

Walkthrough

This PR adds cast_stored/2 implementations to AshGeo.GeoJson.Use that properly deserialize GeoJSON maps from storage by JSON round-tripping through Jason and decoding via Geo.JSON, with corresponding test coverage for atom-keyed maps, string-keyed maps, and nil inputs.

Changes

GeoJSON Stored Value Deserialization

Layer / File(s)	Summary
GeoJSON stored value deserialization implementation and tests lib/ash_geo/geo_json.ex, test/ash_geo_test.exs	cast_stored/2 clauses for typed-maps (%{type: _}) and non-struct maps use Jason.encode/1, Jason.decode/1, and Geo.JSON.decode/1 to deserialize stored GeoJSON values, with test cases verifying correct handling of atom-keyed maps, string-keyed maps, and nil inputs.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

A rabbit hops through JSON streams,
Where GeoJSON dreams take shape with themes,
Maps decode from storage's vault so deep,
Round-tripping through the data's keep,
Geo.JSON makes the coordinates leap! 🐰✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main fix: adding support for GeoJSON maps in cast_stored/2, which is the core change across both modified files.
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.

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✨ Finishing Touches

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• Create PR with unit tests

---

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[matt-beanland]

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