ViewComponent · joelhawksley · Jul 24, 2026 · Jul 24, 2026
diff --git a/.audition-baseline.json b/.audition-baseline.json
diff --git a/.audition.yml b/.audition.yml
@@ -0,0 +1,9 @@
+# Audition — Ractor-readiness checks (https://github.com/yaroslav/audition)
+#
+# Known findings are recorded in .audition-baseline.json so CI fails only on
+# *new* findings. Regenerate the baseline with:
+#   audition . --write-baseline
+#
+# Silence a single line inline, rubocop-style:
+#   risky_call # audition:disable <check-name>
+fail_on: error
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
@@ -104,3 +104,18 @@ jobs:
         bundler-cache: true
     - name: YARD Lint
       run: bundle exec yard-lint lib/
+  audition:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Setup Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: 4.0
+    # audition needs Ruby 4.0+; installed standalone since rubydex is a
+    # precompiled native gem. Fails only on findings not in
+    # .audition-baseline.json. Static-only skips Ractor issues in dependencies.
+    - name: Install audition
+      run: gem install audition
+    - name: Audition (Ractor readiness)
+      run: audition . --static-only --plain
diff --git a/Gemfile b/Gemfile
@@ -14,6 +14,7 @@ group :development, :test do
   gem "allocation_stats"
   gem "appraisal", "~> 2"
   gem "appraisal-run", "~> 1.1"
+  gem "audition", require: false
   gem "benchmark-ips", "~> 2"
   gem "better_html"
   gem "bundler"

diff --git a/Gemfile.lock b/Gemfile.lock
@@ -93,6 +93,12 @@ GEM
       thor (>= 0.14.0)
     appraisal-run (1.1.0)
     ast (2.4.3)
+    audition (0.2.1)
+      pastel (>= 0.8)
+      prism (>= 1.0)
+      rubydex (>= 0.2)
+      table_tennis (>= 1.0)
+      tty-link (>= 0.2)
     base64 (0.3.0)
     benchmark-ips (2.15.1)
     better_html (2.2.0)
@@ -116,6 +122,7 @@ GEM
     concurrent-ruby (1.3.8)
     connection_pool (3.0.2)
     crass (1.0.7)
+    csv (3.3.5)
     cuprite (0.17)
       capybara (~> 3.0)
       ferrum (~> 0.17.0)
@@ -138,6 +145,7 @@ GEM
       concurrent-ruby (~> 1.1)
       webrick (~> 1.7)
       websocket-driver (~> 0.7)
+    ffi (1.17.4)
     globalid (1.3.0)
       activesupport (>= 6.1)
     haml (7.2.0)
@@ -181,6 +189,7 @@ GEM
       net-smtp
     marcel (1.1.0)
     matrix (0.4.3)
+    memo_wise (1.13.0)
     method_source (1.1.0)
     mini_mime (1.1.5)
     minitest (6.0.6)
@@ -213,10 +222,13 @@ GEM
       racc (~> 1.4)
     nokogiri (1.19.4-x86_64-linux-musl)
       racc (~> 1.4)
+    paint (2.3.0)
     parallel (1.28.0)
     parser (3.3.12.0)
       ast (~> 2.4.1)
       racc
+    pastel (0.8.0)
+      tty-color (~> 0.5)
     pp (0.6.3)
       prettyprint
     prettyprint (0.2.0)
@@ -326,6 +338,7 @@ GEM
       rubocop (>= 1.75.0, < 2.0)
       rubocop-ast (>= 1.47.1, < 2.0)
     ruby-progressbar (1.13.0)
+    rubydex (0.3.0)
     rubyzip (3.3.0)
     securerandom (0.4.1)
     selenium-webdriver (4.44.0)
@@ -364,6 +377,12 @@ GEM
       lint_roller (~> 1.1)
       rubocop-performance (~> 1.26.0)
     stringio (3.2.0)
+    table_tennis (1.0.0)
+      csv (~> 3.3)
+      ffi (~> 1.17)
+      memo_wise (~> 1.13)
+      paint (~> 2.3)
+      unicode-display_width (~> 3.2)
     tailwindcss-rails (4.6.0)
       railties (>= 7.0.0)
       tailwindcss-ruby (~> 4.0)
@@ -381,6 +400,8 @@ GEM
     tilt (2.7.0)
     timeout (0.6.1)
     tsort (0.2.0)
+    tty-color (0.6.0)
+    tty-link (0.2.0)
     turbo-rails (2.0.23)
       actionpack (>= 7.1.0)
       railties (>= 7.1.0)
@@ -422,6 +443,7 @@ DEPENDENCIES
   allocation_stats
   appraisal (~> 2)
   appraisal-run (~> 1.1)
+  audition
   benchmark-ips (~> 2)
   better_html
   bundler
@@ -478,6 +500,7 @@ CHECKSUMS
   appraisal (2.5.0) sha256=36989221be127913b0dba8d114da2001e6b2dceea7bd4951200eaba764eed3ce
   appraisal-run (1.1.0) sha256=93179b8fe4d7a3469a703dab69deccc88432bfe43f979acdebbe514e21af9789
   ast (2.4.3) sha256=954615157c1d6a382bc27d690d973195e79db7f55e9765ac7c481c60bdb4d383
+  audition (0.2.1) sha256=7a6661ee96e3fbb5bf97a97b23df9f5649ae4dfd3599ab115192cb62e10a7030
   base64 (0.3.0) sha256=27337aeabad6ffae05c265c450490628ef3ebd4b67be58257393227588f5a97b
   benchmark-ips (2.15.1) sha256=07a1a9f3c6105ecaf68c174fc3fbcddd71a0e9ada6236ae03093a0dcfd812d59
   better_html (2.2.0) sha256=e68ab66ab09696b708333bbf35e8aa3c107500ba7892f528e2111624bdd8cf76
@@ -488,6 +511,7 @@ CHECKSUMS
   concurrent-ruby (1.3.8) sha256=b2f1be836e968ccc78ccfce277ea79c72a88633f22306782c16ff23fb415d1e1
   connection_pool (3.0.2) sha256=33fff5ba71a12d2aa26cb72b1db8bba2a1a01823559fb01d29eb74c286e62e0a
   crass (1.0.7) sha256=94868719948664c89ddcaf0a37c65048413dfcb1c869470a5f7a7ceb5390b295
+  csv (3.3.5) sha256=6e5134ac3383ef728b7f02725d9872934f523cb40b961479f69cf3afa6c8e73f
   cuprite (0.17) sha256=b140d5dc70d08b97ad54bcf45cd95d0bd430e291e9dffe76fff851fddd57c12b
   date (3.5.1) sha256=750d06384d7b9c15d562c76291407d89e368dda4d4fff957eb94962d325a0dc0
   diff-lcs (1.6.2) sha256=9ae0d2cba7d4df3075fe8cd8602a8604993efc0dfa934cff568969efb1909962
@@ -497,6 +521,7 @@ CHECKSUMS
   erb_lint (0.9.0) sha256=dfb5e40ad839e8d1f0d56ca85ec9a7ac4c9cd966ec281138282f35b323ca7c31
   erubi (1.13.1) sha256=a082103b0885dbc5ecf1172fede897f9ebdb745a4b97a5e8dc63953db1ee4ad9
   ferrum (0.17.1) sha256=51d591120fc593e5a13b5d9d6474389f5145bb92a91e36eab147b5d096c8cbe7
+  ffi (1.17.4) sha256=bcd1642e06f0d16fc9e09ac6d49c3a7298b9789bcb58127302f934e437d60acf
   globalid (1.3.0) sha256=05c639ad6eb4594522a0b07983022f04aa7254626ab69445a0e493aa3786ff11
   haml (7.2.0) sha256=87fd2b71f7feab1724337b090a7d767f5ab2d42f08c974f3ead673f18cfcd55a
   herb (0.9.2) sha256=88364c6394740f58d3795cb754a9f4a861631fe6464f250ac0e739d50727e13c
@@ -521,6 +546,7 @@ CHECKSUMS
   mail (2.9.0) sha256=6fa6673ecd71c60c2d996260f9ee3dd387d4673b8169b502134659ece6d34941
   marcel (1.1.0) sha256=fdcfcfa33cc52e93c4308d40e4090a5d4ea279e160a7f6af988260fa970e0bee
   matrix (0.4.3) sha256=a0d5ab7ddcc1973ff690ab361b67f359acbb16958d1dc072b8b956a286564c5b
+  memo_wise (1.13.0) sha256=30220c38c4cef410849bc73553c58664dc2c91c6379e4a1df22aea02358b716b
   method_source (1.1.0) sha256=181301c9c45b731b4769bc81e8860e72f9161ad7d66dd99103c9ab84f560f5c5
   mini_mime (1.1.5) sha256=8681b7e2e4215f2a159f9400b5816d85e9d8c6c6b491e96a12797e798f8bccef
   minitest (6.0.6) sha256=153ea36d1d987a62942382b61075745042a2b3123b1cd48f4c3675af9cc7d6f1
@@ -538,8 +564,10 @@ CHECKSUMS
   nokogiri (1.19.4-x86_64-darwin) sha256=7fd17057d3e1f00e9954a74b3cd76595d3d4a5ef233b7ed9599047c204f70551
   nokogiri (1.19.4-x86_64-linux-gnu) sha256=379fae440b28915e3f19d752ce2dcf8465ed2b2fbefd2a7ca0dd497bc981a06a
   nokogiri (1.19.4-x86_64-linux-musl) sha256=17dfb7c1fa194ae02fbf7c51a7afc8d278045ab3fdacfd86f91d02d7b274470b
+  paint (2.3.0) sha256=327d623e4038619d5bd99ae5db07973859cd78400c7f0329eea283cef8e83be5
   parallel (1.28.0) sha256=33e6de1484baf2524792d178b0913fc8eb94c628d6cfe45599ad4458c638c970
   parser (3.3.12.0) sha256=21a6d7f755d5a24dfbdc6e6b772e4e879a52e7631a88bc5a3a134606052c9828
+  pastel (0.8.0) sha256=481da9fb7d2f6e6b1a08faf11fa10363172dc40fd47848f096ae21209f805a75
   pp (0.6.3) sha256=2951d514450b93ccfeb1df7d021cae0da16e0a7f95ee1e2273719669d0ab9df6
   prettyprint (0.2.0) sha256=2bc9e15581a94742064a3cc8b0fb9d45aae3d03a1baa6ef80922627a0766f193
   prism (1.9.0) sha256=7b530c6a9f92c24300014919c9dcbc055bf4cdf51ec30aed099b06cd6674ef85
@@ -575,6 +603,7 @@ CHECKSUMS
   rubocop-md (2.0.4) sha256=0d076b6b5e99dea2ddc928c4bd702497decb9a8400da7808091e02ebcafcfb93
   rubocop-performance (1.26.1) sha256=cd19b936ff196df85829d264b522fd4f98b6c89ad271fa52744a8c11b8f71834
   ruby-progressbar (1.13.0) sha256=80fc9c47a9b640d6834e0dc7b3c94c9df37f08cb072b7761e4a71e22cff29b33
+  rubydex (0.3.0) sha256=902ba4546c548de6a1908acee54cf3f5b998f01c87e2ad6fbd708011774df4e5
   rubyzip (3.3.0) sha256=a372fc67892a4f8c0bc8ec906b720353d8e48807a64b2e63adf99b1e3583a034
   securerandom (0.4.1) sha256=cc5193d414a4341b6e225f0cb4446aceca8e50d5e1888743fac16987638ea0b1
   selenium-webdriver (4.44.0) sha256=6f1df072529af369589c46f0e01132952aabb250cfd683c274d74dc1eb5d8477
@@ -588,6 +617,7 @@ CHECKSUMS
   standard-custom (1.0.2) sha256=424adc84179a074f1a2a309bb9cf7cd6bfdb2b6541f20c6bf9436c0ba22a652b
   standard-performance (1.9.0) sha256=49483d31be448292951d80e5e67cdcb576c2502103c7b40aec6f1b6e9c88e3f2
   stringio (3.2.0) sha256=c37cb2e58b4ffbd33fe5cd948c05934af997b36e0b6ca6fdf43afa234cf222e1
+  table_tennis (1.0.0) sha256=955f76ca4debd42ee88682af8d4554a74d533c89de4f1581bc37855b15faa956
   tailwindcss-rails (4.6.0) sha256=d99512867173d55c5ef8890427682299d8539f550cec1408b3d8667a538bd365
   tailwindcss-ruby (4.3.1) sha256=ced3198e057da98f21cb281f4821ac8882a2899047066895ba181caf312620c1
   tailwindcss-ruby (4.3.1-aarch64-linux-gnu) sha256=b42af5fdb7ade3f3f70cda217c288986cc6b773601437b8deb80ea229a96680c
@@ -602,6 +632,8 @@ CHECKSUMS
   tilt (2.7.0) sha256=0d5b9ba69f6a36490c64b0eee9f6e9aad517e20dcc848800a06eb116f08c6ab3
   timeout (0.6.1) sha256=78f57368a7e7bbadec56971f78a3f5ecbcfb59b7fcbb0a3ed6ddc08a5094accb
   tsort (0.2.0) sha256=9650a793f6859a43b6641671278f79cfead60ac714148aabe4e3f0060480089f
+  tty-color (0.6.0) sha256=6f9c37ca3a4e2367fb2e6d09722762647d6f455c111f05b59f35730eeb24332a
+  tty-link (0.2.0) sha256=82fa3284910c250c3e10feef0f2d491717467c029c3eb3ac4b4a7c63fddcbfe5
   turbo-rails (2.0.23) sha256=ee0d90733aafff056cf51ff11e803d65e43cae258cc55f6492020ec1f9f9315f
   tzinfo (2.0.6) sha256=8daf828cc77bcf7d63b0e3bdb6caa47e2272dcfaf4fbfe46f8c3a9df087a829b
   unicode-display_width (3.2.0) sha256=0cdd96b5681a5949cdbc2c55e7b420facae74c4aaf9a9815eee1087cb1853c42

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
@@ -10,6 +10,10 @@
 
 ## main
 
+* Add [audition](https://github.com/yaroslav/audition) Ractor-readiness checks to CI. Applied safe `.freeze` auto-fixes to string constants in `ViewComponent::Errors` and baselined existing findings so the gate fails only on new Ractor-isolation violations.
+
+    *Joel Hawksley*
+
 * Update link to GOV.UK Components library in resources list to govuk-components.x-govuk.org
 
     *Peter Yates*

diff --git a/lib/view_component/errors.rb b/lib/view_component/errors.rb
@@ -9,7 +9,7 @@ class DuplicateSlotContentError < StandardError
     MESSAGE =
       "It looks like a block was provided after calling `with_content` on COMPONENT, " \
       "which means that ViewComponent doesn't know which content to use.\n\n" \
-      "To fix this issue, use either `with_content` or a block."
+      "To fix this issue, use either `with_content` or a block.".freeze
 
     def initialize(klass_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s))
@@ -25,13 +25,13 @@ def initialize(errors, templates = nil)
   end
 
   class MultipleInlineTemplatesError < BaseError
-    MESSAGE = "Inline templates can only be defined once per-component."
+    MESSAGE = "Inline templates can only be defined once per-component.".freeze
   end
 
   class MissingPreviewTemplateError < StandardError
     MESSAGE =
       "A preview template for example EXAMPLE doesn't exist.\n\n" \
-      "To fix this issue, create a template for the example."
+      "To fix this issue, create a template for the example.".freeze
 
     def initialize(example)
       super(MESSAGE.gsub("EXAMPLE", example))
@@ -41,7 +41,7 @@ def initialize(example)
   class MissingTemplateError < StandardError
     MESSAGE =
       "No templates for COMPONENT match the request DETAIL.\n\n" \
-      "To fix this issue, provide a suitable template."
+      "To fix this issue, provide a suitable template.".freeze
 
     def initialize(component, request_detail)
       detail = {
@@ -58,7 +58,7 @@ class DuplicateContentError < StandardError
     MESSAGE =
       "It looks like a block was provided after calling `with_content` on COMPONENT, " \
       "which means that ViewComponent doesn't know which content to use.\n\n" \
-      "To fix this issue, use either `with_content` or a block."
+      "To fix this issue, use either `with_content` or a block.".freeze
 
     def initialize(klass_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s))
@@ -70,7 +70,7 @@ class MissingCollectionArgumentError < StandardError
       "The initializer for COMPONENT doesn't accept the parameter `PARAMETER`, " \
       "which is required to render it as a collection.\n\n" \
       "To fix this issue, update the initializer to accept `PARAMETER`.\n\n" \
-      "See [the collections docs](https://viewcomponent.org/guide/collections.html) for more information on rendering collections."
+      "See [the collections docs](https://viewcomponent.org/guide/collections.html) for more information on rendering collections.".freeze
 
     def initialize(klass_name, parameter)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("PARAMETER", parameter.to_s))
@@ -80,7 +80,7 @@ def initialize(klass_name, parameter)
   class ReservedParameterError < StandardError
     MESSAGE =
       "COMPONENT initializer can't accept the parameter `PARAMETER`, as it will override a " \
-      "public ViewComponent method. To fix this issue, rename the parameter."
+      "public ViewComponent method. To fix this issue, rename the parameter.".freeze
 
     def initialize(klass_name, parameter)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("PARAMETER", parameter.to_s))
@@ -90,14 +90,14 @@ def initialize(klass_name, parameter)
   class InvalidCollectionArgumentError < BaseError
     MESSAGE =
       "The value of the first argument passed to `with_collection` isn't a valid collection. " \
-      "Make sure it responds to `to_ary`."
+      "Make sure it responds to `to_ary`.".freeze
   end
 
   class ContentSlotNameError < StandardError
     MESSAGE =
       "COMPONENT declares a slot named content, which is a reserved word in ViewComponent.\n\n" \
       "Content passed to a ViewComponent as a block is captured and assigned to the `content` accessor without having to create an explicit slot.\n\n" \
-      "To fix this issue, either use the `content` accessor directly or choose a different slot name."
+      "To fix this issue, either use the `content` accessor directly or choose a different slot name.".freeze
 
     def initialize(klass_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s))
@@ -107,7 +107,7 @@ def initialize(klass_name)
   class InvalidSlotDefinitionError < BaseError
     MESSAGE =
       "Invalid slot definition. Please pass a class, " \
-      "string, or callable (that is proc, lambda, etc)"
+      "string, or callable (that is proc, lambda, etc)".freeze
   end
 
   class InvalidSlotNameError < StandardError
@@ -118,7 +118,7 @@ class SlotPredicateNameError < InvalidSlotNameError
       "COMPONENT declares a slot named SLOT_NAME, which ends with a question mark.\n\n" \
       "This isn't allowed because the ViewComponent framework already provides predicate " \
       "methods ending in `?`.\n\n" \
-      "To fix this issue, choose a different name."
+      "To fix this issue, choose a different name.".freeze
 
     def initialize(klass_name, slot_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
@@ -128,7 +128,7 @@ def initialize(klass_name, slot_name)
   class RedefinedSlotError < StandardError
     MESSAGE =
       "COMPONENT declares the SLOT_NAME slot multiple times.\n\n" \
-      "To fix this issue, choose a different slot name."
+      "To fix this issue, choose a different slot name.".freeze
 
     def initialize(klass_name, slot_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
@@ -138,7 +138,7 @@ def initialize(klass_name, slot_name)
   class ReservedSingularSlotNameError < InvalidSlotNameError
     MESSAGE =
       "COMPONENT declares a slot named SLOT_NAME, which is a reserved word in the ViewComponent framework.\n\n" \
-      "To fix this issue, choose a different name."
+      "To fix this issue, choose a different name.".freeze
 
     def initialize(klass_name, slot_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
@@ -148,7 +148,7 @@ def initialize(klass_name, slot_name)
   class ReservedPluralSlotNameError < InvalidSlotNameError
     MESSAGE =
       "COMPONENT declares a slot named SLOT_NAME, which is a reserved word in the ViewComponent framework.\n\n" \
-      "To fix this issue, choose a different name."
+      "To fix this issue, choose a different name.".freeze
 
     def initialize(klass_name, slot_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
@@ -158,15 +158,15 @@ def initialize(klass_name, slot_name)
   class UncountableSlotNameError < InvalidSlotNameError
     MESSAGE =
       "COMPONENT declares a slot named SLOT_NAME, which is an uncountable word\n\n" \
-      "To fix this issue, choose a different name."
+      "To fix this issue, choose a different name.".freeze
 
     def initialize(klass_name, slot_name)
       super(MESSAGE.gsub("COMPONENT", klass_name.to_s).gsub("SLOT_NAME", slot_name.to_s))
     end
   end
 
   class ContentAlreadySetForPolymorphicSlotError < StandardError
-    MESSAGE = "Content for slot SLOT_NAME has already been provided."
+    MESSAGE = "Content for slot SLOT_NAME has already been provided.".freeze
 
     def initialize(slot_name)
       super(MESSAGE.gsub("SLOT_NAME", slot_name.to_s))
@@ -176,7 +176,7 @@ def initialize(slot_name)
   class NilWithContentError < BaseError
     MESSAGE =
       "No content provided to `#with_content` for #{self}.\n\n" \
-      "To fix this issue, pass a value."
+      "To fix this issue, pass a value.".freeze
   end
 
   class TranslateCalledBeforeRenderError < BaseError
@@ -185,7 +185,7 @@ class TranslateCalledBeforeRenderError < BaseError
       "on the view context that only exists once a ViewComponent is passed to " \
       "the Rails render pipeline.\n\n" \
       "It's sometimes possible to fix this issue by moving code dependent on " \
-      "`#translate` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void)."
+      "`#translate` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void).".freeze
   end
 
   class HelpersCalledBeforeRenderError < BaseError
@@ -194,7 +194,7 @@ class HelpersCalledBeforeRenderError < BaseError
       "on the view context that only exists once a ViewComponent is passed to " \
       "the Rails render pipeline.\n\n" \
       "It's sometimes possible to fix this issue by moving code dependent on " \
-      "`#helpers` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void)."
+      "`#helpers` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void).".freeze
   end
 
   class ControllerCalledBeforeRenderError < BaseError
@@ -203,17 +203,17 @@ class ControllerCalledBeforeRenderError < BaseError
       "on the view context that only exists once a ViewComponent is passed to " \
       "the Rails render pipeline.\n\n" \
       "It's sometimes possible to fix this issue by moving code dependent on " \
-      "`#controller` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void)."
+      "`#controller` to a [`#before_render` method](https://viewcomponent.org/api.html#before_render--void).".freeze
   end
 
   class SystemTestControllerNefariousPathError < BaseError
-    MESSAGE = "ViewComponent SystemTest controller attempted to load a file outside of the expected directory."
+    MESSAGE = "ViewComponent SystemTest controller attempted to load a file outside of the expected directory.".freeze
   end
 
   class AlreadyDefinedPolymorphicSlotSetterError < StandardError
     MESSAGE =
       "A method called 'SETTER_METHOD_NAME' already exists and would be overwritten by the 'SETTER_NAME' polymorphic " \
-      "slot setter.\n\nPlease choose a different setter name."
+      "slot setter.\n\nPlease choose a different setter name.".freeze
 
     def initialize(setter_method_name, setter_name)
       super(MESSAGE.gsub("SETTER_METHOD_NAME", setter_method_name.to_s).gsub("SETTER_NAME", setter_name.to_s))