From 1f35c139e0c1859258ec54cf37884f8eebddcd5c Mon Sep 17 00:00:00 2001
From: Shinichi Maeshima <netwillnet@gmail.com>
Date: Tue, 29 Sep 2026 11:12:46 +0900
Subject: [PATCH] Use `shared` key instead of `default` in cache.yml

The README uses `default` as the top-level key in the `config/cache.yml`
sample. It looks like a place to define defaults available to every
environment, but it is actually not a meaningful key name. Shared
settings can be achieved with YAML anchors and aliases, but the current
example is easy to misunderstand. Moreover, in the example,
`size_estimate_samples: 1000` ends up being a setting that is never used.

`config/cache.yml` is loaded with `config_for`:
https://github.com/rails/solid_cache/blob/da70ef4f8f9c5ad6490b3994cd4d67dcf5e3659a/lib/solid_cache/engine.rb#L21

`config_for` treats `shared` as the defaults for every environment, so
switch to it to reduce confusion.

The template generated by `bin/rails solid_cache:install` is updated
accordingly.
---
 README.md                                            | 12 ++++++------
 .../install/templates/config/cache.yml.tt            |  9 +--------
 .../solid_cache/install_generator_test.rb            |  9 +--------
 3 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/README.md b/README.md
index a6942ce..b0a187d 100644
--- a/README.md
+++ b/README.md
@@ -56,25 +56,25 @@ Configuration will be read from `config/cache.yml` or `config/solid_cache.yml`.
 The format of the file is:
 
 ```yml
-default:
-  store_options: &default_store_options
+shared:
+  store_options:
     max_age: <%= 60.days.to_i %>
     namespace: <%= Rails.env %>
   size_estimate_samples: 1000
 
-development: &development
+development:
   database: cache
   store_options:
-    <<: *default_store_options
     max_size: <%= 256.gigabytes %>
 
-production: &production
+production:
   databases: [production_cache1, production_cache2]
   store_options:
-    <<: *default_store_options
     max_size: <%= 256.gigabytes %>
 ```
 
+The `shared` key is read by Rails' `config_for` and deep merged into the configuration of every environment, with the environment's own values taking precedence.
+
 For the full list of keys for `store_options` see [Cache configuration](#cache-configuration). Any options passed to the cache lookup will overwrite those specified here.
 
 After running `solid_cache:install`, `environments/production.rb` will replace your cache store with Solid Cache, but you can also do this manually:
diff --git a/lib/generators/solid_cache/install/templates/config/cache.yml.tt b/lib/generators/solid_cache/install/templates/config/cache.yml.tt
index 70a2ac6..52b4a16 100644
--- a/lib/generators/solid_cache/install/templates/config/cache.yml.tt
+++ b/lib/generators/solid_cache/install/templates/config/cache.yml.tt
@@ -1,16 +1,9 @@
-default: &default
+shared:
   store_options:
     # Cap age of oldest cache entry to fulfill retention policies
     # max_age: <%%= 60.days.to_i %>
     max_size: <%%= 256.megabytes %>
     namespace: <%%= Rails.env %>
 
-development:
-  <<: *default
-
-test:
-  <<: *default
-
 production:
   database: <%= ENV.fetch("DATABASE", "cache") %>
-  <<: *default
diff --git a/test/lib/generators/solid_cache/solid_cache/install_generator_test.rb b/test/lib/generators/solid_cache/solid_cache/install_generator_test.rb
index fd12cbc..83ce8f8 100644
--- a/test/lib/generators/solid_cache/solid_cache/install_generator_test.rb
+++ b/test/lib/generators/solid_cache/solid_cache/install_generator_test.rb
@@ -71,22 +71,15 @@ class SolidCache::InstallGeneratorTest < Rails::Generators::TestCase
     private
       def expected_cache_config
         <<~YAML
-          default: &default
+          shared:
             store_options:
               # Cap age of oldest cache entry to fulfill retention policies
               # max_age: <%= 60.days.to_i %>
               max_size: <%= 256.megabytes %>
               namespace: <%= Rails.env %>
 
-          development:
-            <<: *default
-
-          test:
-            <<: *default
-
           production:
             database: cache
-            <<: *default
         YAML
       end
   end