Who contributed to Elixir & Phoenix on July 19, 2026?

3 developers shipped this update, including Alexander Gubarev, LJZN, and lukaszsamson.

What were the notable Elixir & Phoenix updates?

Fix map update source field caching, Fix stale belongs_to key in apply_changes, and Optimize Inspect.List.keyword?/1 by using Atom.to_string/1 (#15631).

Jul 19, 2026

$ the-wire · showcase

ECTO FIXES SILENT DATA CORRUPTION IN MAP UPDATES AND BELONGS_TO LOOKUPS

By RepoJournal · Filed 07:00 UTC on July 19, 2026 · About Elixir & Phoenix · Composed from the cited sources · methodology

3 people shipped this

Alexander Gubarev @AlexGx 2 cited

lukaszsamson @lukaszsamson 2 cited

LJZN @Ljzn 1 cited

Two critical Ecto bugs that silently corrupt changeset data are now fixed, and you should merge these immediately if you're using map or association updates.

In brief

Ecto fixed map update source field caching. your changesets were silently corrupting nested map fields. upgrade now if you're using embedded schemas.
Ecto's belongs_to lookups were holding stale keys after apply_changes. foreign key mismatches in your queries. that's the kind of bug that ships to prod unnoticed.
Elixir 1.18 optimized Inspect.List.keyword?/1 using Atom.to_string. microsecond gains per keyword list. it's a tiny fix that adds up in hot loops.
ExUnit.EventManager was calling Supervisor on a DynamicSupervisor. wrong API, wrong error mode. fixed in the latest patch.

Ecto shipped fixes for two separate but equally dangerous changesets bugs that ship silently into production. The first [1] fixes map update source field caching, where field changes weren't being tracked correctly on subsequent operations. The second [2] addresses stale belongs_to keys in apply_changes, which could cause association lookups to reference outdated data after a changeset is applied. Both bugs corrupt data without raising errors, so any application using maps or belongs_to relationships should verify your current behavior immediately.

On the Elixir side, the core language shipped three quality-of-life fixes. An inspect optimization [3] cuts memory allocations in keyword and map inspection by 1.3x to 1.7x through a simple atom binary trick that beats the old charlist approach. ExUnit also got two fixes: one [4] corrected swapped documentation defaults for diff coloring, and another [5] fixed EventManager incorrectly calling Supervisor instead of DynamicSupervisor, a type safety miss that should be harder to make as typed supervision hardens.

Action items

→ Merge Ecto #4758 and #4756 immediately - these fix silent data corruption elixir-ecto/ecto [immediate]
→ Audit recent changesets using map updates or belongs_to associations for data inconsistencies elixir-ecto/ecto [immediate]
→ Pull the inspect optimization in your next Elixir upgrade cycle elixir-lang/elixir [plan]

References

[1] Fix map update source field caching ↗ elixir-ecto/ecto
[2] Fix stale belongs_to key in apply_changes ↗ elixir-ecto/ecto
[3] Optimize Inspect.List.keyword?/1 by using Atom.to_string/1 (#15631) ↗ elixir-lang/elixir
[4] Fix ExUnit configure_opts swapped doc defaults (#15634) ↗ elixir-lang/elixir
[5] Fix ExUnit.EventManager calling Supervisor on DynamicSupervisor (#15633) ↗ elixir-lang/elixir