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Diffstat (limited to 'guides/source/upgrading_ruby_on_rails.md')
| -rw-r--r-- | guides/source/upgrading_ruby_on_rails.md | 277 |
1 files changed, 262 insertions, 15 deletions
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md index 79bad8f4ed..b8a5c39f39 100644 --- a/guides/source/upgrading_ruby_on_rails.md +++ b/guides/source/upgrading_ruby_on_rails.md @@ -85,30 +85,31 @@ Rails 6.1. You are encouraged to enable `config.force_ssl` to enforce HTTPS connections throughout your application. If you need to exempt certain endpoints from redirection, you can use `config.ssl_options` to configure that behavior. -### Purpose in signed or encrypted cookie is now embedded in the cookies values +### Purpose and expiry metadata is now embedded inside signed and encrypted cookies for increased security -To improve security, Rails now embeds the purpose information in encrypted or signed cookies value. -Rails can now thwart attacks that attempt to copy signed/encrypted value +To improve security, Rails embeds the purpose and expiry metadata inside encrypted or signed cookies value. + +Rails can then thwart attacks that attempt to copy the signed/encrypted value of a cookie and use it as the value of another cookie. -This new embed information make those cookies incompatible with versions of Rails older than 6.0. +This new embed metadata make those cookies incompatible with versions of Rails older than 6.0. -If you require your cookies to be read by 5.2 and older, or you are still validating your 6.0 deploy and want -to allow you to rollback set +If you require your cookies to be read by Rails 5.2 and older, or you are still validating your 6.0 deploy and want +to be able to rollback set `Rails.application.config.action_dispatch.use_cookies_with_metadata` to `false`. -### ActionCable javascript API Changes +### Action Cable JavaScript API Changes -The ActionCable javascript package has been converted from CoffeeScript +The Action Cable JavaScript package has been converted from CoffeeScript to ES2015, and we now publish the source code in the npm distribution. -This change includes some breaking changes to optional parts of the -ActionCable javascript API: +This release includes some breaking changes to optional parts of the +Action Cable JavaScript API: - Configuration of the WebSocket adapter and logger adapter have been moved from properties of `ActionCable` to properties of `ActionCable.adapters`. - If you are currently configuring these adapters you will need to make - these changes when upgrading: + If you are configuring these adapters you will need to make + these changes: ```diff - ActionCable.WebSocket = MyWebSocket @@ -121,8 +122,8 @@ ActionCable javascript API: - The `ActionCable.startDebugging()` and `ActionCable.stopDebugging()` methods have been removed and replaced with the property - `ActionCable.logger.enabled`. If you are currently using these methods you - will need to make these changes when upgrading: + `ActionCable.logger.enabled`. If you are using these methods you + will need to make these changes: ```diff - ActionCable.startDebugging() @@ -133,6 +134,252 @@ ActionCable javascript API: + ActionCable.logger.enabled = false ``` +### Autoloading + +The default configuration for Rails 6 + +```ruby +# config/application.rb + +config.load_defaults "6.0" +``` + +enables `zeitwerk` autoloading mode on CRuby. In that mode, autoloading, reloading, and eager loading are managed by [Zeitwerk](https://github.com/fxn/zeitwerk). + +#### Public API + +In general, applications do not need to use the API of Zeitwerk directly. Rails sets things up according to the existing contract: `config.autoload_paths`, `config.cache_classes`, etc. + +While applications should stick to that interface, the actual Zeitwerk loader object can be accessed as + +```ruby +Rails.autoloaders.main +``` + +That may be handy if you need to preload STIs or configure a custom inflector, for example. + +#### Project Structure + +If the application being upgraded autoloads correctly, the project structure should be already mostly compatible. + +However, `classic` mode infers file names from missing constant names (`underscore`), whereas `zeitwerk` mode infers constant names from file names (`camelize`). These helpers are not always inverse of each other, in particular if acronyms are involved. For instance, `"FOO".underscore` is `"foo"`, but `"foo".camelize` is `"Foo"`, not `"FOO"`. Compatibility can be checked by setting `classic` mode first temporarily: + +```ruby +# config/application.rb + +config.load_defaults "6.0" +config.autoloader = :classic +``` + +and then running + +``` +bin/rails zeitwerk:check +``` + +When all is good, you can delete `config.autoloader = :classic`. + +#### require_dependency + +All known use cases of `require_dependency` have been eliminated, you should grep the project and delete them. + +In the case of STIs with a hierarchy of more than two levels, you can preload the leaves of the hierarchy in an initializer: + +```ruby +# config/initializers/preload_stis.rb + +# By preloading leaves, the hierarchy is loaded upwards following +# the references to superclasses in the class definitions. +sti_leaves = %w( + app/models/leaf1.rb + app/models/leaf2.rb + app/models/leaf3.rb +) +Rails.autoloaders.main.preload(sti_leaves) +``` + +#### Qualified names in class and module definitions + +You can now robustly use constant paths in class and module definitions: + +```ruby +# Autoloading in this class' body matches Ruby semantics now. +class Admin::UsersController < ApplicationController + # ... +end +``` + +A gotcha to be aware of is that, depending on the order of execution, the classic autoloader could sometimes be able to autoload `Foo::Wadus` in + +```ruby +class Foo::Bar + Wadus +end +``` + +That does not match Ruby semantics because `Foo` is not in the nesting, and won't work at all in `zeitwerk` mode. If you find such corner case you can use the qualified name `Foo::Wadus`: + +```ruby +class Foo::Bar + Foo::Wadus +end +``` + +or add `Foo` to the nesting: + +```ruby +module Foo + class Bar + Wadus + end +end +``` + +#### Concerns + +You can autoload and eager load from a standard structure like + +``` +app/models +app/models/concerns +``` + +In that case, `app/models/concerns` is assumed to be a root directory (because it belongs to the autoload paths), and it is ignored as namespace. So, `app/models/concerns/foo.rb` should define `Foo`, not `Concerns::Foo`. + +The `Concerns::` namespace worked with the classic autoloader as a side-effect of the implementation, but it was not really an intended behavior. An application using `Concerns::` needs to rename those classes and modules to be able to run in `zeitwerk` mode. + +#### Autoloaded Constants and Explicit Namespaces + +If a namespace is defined in a file, as `Hotel` is here: + +``` +app/models/hotel.rb # Defines Hotel. +app/models/hotel/pricing.rb # Defines Hotel::Pricing. +``` + +the `Hotel` constant has to be set using the `class` or `module` keywords. For example: + +```ruby +class Hotel +end +``` + +is good. + +Alternatives like + +```ruby +Hotel = Class.new +``` + +or + +```ruby +Hotel = Struct.new +``` + +won't work, child objects like `Hotel::Pricing` won't be found. + +This restriction only applies to explicit namespaces. Classes and modules not defining a namespace can be defined using those idioms. + +#### One file, one constant (at the same top-level) + +In `classic` mode you could technically define several constants at the same top-level and have them all reloaded. For example, given + +```ruby +# app/models/foo.rb + +class Foo +end + +class Bar +end +``` + +while `Bar` could not be autoloaded, autoloading `Foo` would mark `Bar` as autoloaded too. This is not the case in `zeitwerk` mode, you need to move `Bar` to its own file `bar.rb`. One file, one constant. + +This affects only to constants at the same top-level as in the example above. Inner classes and modules are fine. For example, consider + +```ruby +# app/models/foo.rb + +class Foo + class InnerClass + end +end +``` + +If the application reloads `Foo`, it will reload `Foo::InnerClass` too. + +#### Spring and the `test` Environment + +Spring reloads the application code if something changes. In the `test` environment you need to enable reloading for that to work: + +```ruby +# config/environments/test.rb + +config.cache_classes = false +``` + +Otherwise you'll get this error: + +``` +reloading is disabled because config.cache_classes is true +``` + +#### Bootsnap + +Bootsnap should be at least version 1.4.2. + +In addition to that, Bootsnap needs to disable the iseq cache due to a bug in the interpreter if running Ruby 2.5. Please make sure to depend on at least Bootsnap 1.4.4 in that case. + +#### `config.add_autoload_paths_to_load_path` + +The new configuration point + +```ruby +config.add_autoload_paths_to_load_path +``` + +is `true` by default for backwards compatibility, but allows you to opt-out from adding the autoload paths to `$LOAD_PATH`. + +This makes sense in most applications, since you never should require a file in `app/models`, for example, and Zeitwerk only uses absolute file names internally. + +By opting-out you optimize `$LOAD_PATH` lookups (less directories to check), and save Bootsnap work and memory consumption, since it does not need to build an index for these directories. + +#### Thread-safety + +In classic mode, constant autoloading is not thread-safe, though Rails has locks in place for example to make web requests thread-safe when autoloading is enabled, as it is common in `development` mode. + +Constant autoloading is thread-safe in `zeitwerk` mode. For example, you can now autoload in multi-threaded scripts executed by the `runner` command. + +#### Globs in config.autoload_paths + +Beware of configurations like + +```ruby +config.autoload_paths += Dir["#{config.root}/lib/**/"] +``` + +Every element of `config.autoload_paths` should represent the top-level namespace (`Object`) and they cannot be nested in consequence (with the exception of `concerns` directories explained above). + +To fix this, just remove the wildcards: + +```ruby +config.autoload_paths << "#{config.root}/lib" +``` + +#### How to Use the Classic Autoloader in Rails 6 + +Applications can load Rails 6 defaults and still use the classic autoloader by setting `config.autoloader` this way: + +```ruby +# config/application.rb + +config.load_defaults "6.0" +config.autoloader = :classic +``` + Upgrading from Rails 5.1 to Rails 5.2 ------------------------------------- @@ -1557,7 +1804,7 @@ config.assets.enabled = true config.assets.version = '1.0' ``` -If your application is using an "/assets" route for a resource you may want change the prefix used for assets to avoid conflicts: +If your application is using an "/assets" route for a resource you may want to change the prefix used for assets to avoid conflicts: ```ruby # Defaults to '/assets' |