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Deprecated Configuration Options

This document lists configuration options that have been deprecated or removed from React on Rails.

For current configuration options, see Configuration.

Removed Options​

immediate_hydration​

Configuration option: ⚠️ REMOVED in v16.2.0 — raises NoMethodError at boot

The config.immediate_hydration setting was removed in v16.2.0. Assigning it in your initializer now raises NoMethodError at boot (no method_missing fallback exists). Remove the line.

Helper parameter: ⚠️ REMOVED in v16.6.0 — logs a one-time warning, then ignored

The immediate_hydration: key passed to react_component, react_component_hash, redux_store, stream_react_component, or buffered_stream_react_component was removed in v16.6.0. Passing it now logs a one-time warning (once per helper per process) and the value is dropped. Delete the key from all helper calls.

Rendered HTML attribute: ⚠️ REMOVED in v16.6.0

The data-immediate-hydration attribute that was previously emitted on hydrated/streamed component elements is no longer rendered. If you have CSS/JS selectors (e.g. [data-immediate-hydration]) or test assertions targeting it, remove them.

Behavior: React on Rails Pro now performs early hydration automatically for streamed components; there is no per-component toggle. Non-Pro apps are still affected by the removals above (the config raises and the helper parameter is ignored), but their hydration behavior is otherwise unchanged — immediate hydration is disabled for non-Pro and was never a per-component option.

See CHANGELOG.md for details.

defer_generated_component_packs​

Status: ⚠️ REMOVED in v17.0.0

Deprecated in v16 and removed in v17. Setting config.defer_generated_component_packs now raises NoMethodError at boot. Use config.generated_component_packs_loading_strategy instead.

Migration:

# Old (removed):
config.defer_generated_component_packs = true   # → :defer
config.defer_generated_component_packs = false  # → delete the line (was a no-op)

# New:
config.generated_component_packs_loading_strategy = :defer  # or :sync

The old option was truthy-gated: only = true had any effect (it set :defer). = false was a no-op that fell through to the default strategy — it did not mean :sync. So migrate = true to :defer, and simply delete = false. Set :sync explicitly only if you specifically relied on synchronous (blocking) pack loading.

If you delete the line without setting generated_component_packs_loading_strategy, the default strategy applies: :async for Pro or :defer for non-Pro on Shakapacker 8.2.0+, and :sync on older Shakapacker.

See CHANGELOG.md for more details.

generated_assets_dirs​

Status: ⚠️ REMOVED in v17.0.0

Deprecated in v16 and removed in v17. Setting config.generated_assets_dirs now raises NoMethodError at boot. Delete the line — public asset paths are determined automatically from public_output_path in config/shakapacker.yml.

skip_display_none​

Status: ⚠️ REMOVED in v17.0.0

Deprecated in v16 and removed in v17. Setting config.skip_display_none now raises NoMethodError at boot. Delete the line — it had no runtime effect.

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