Handlers are pluggable semantic parsers for YARD's code generation phase. They allow developers to control what information gets generated by YARD, giving them the ability to, for instance, document any Ruby DSLs that a customized framework may use. A good example of this would be the ability to document and generate meta data for the 'describe' declaration of the RSpec testing framework by simply adding a handler for such a keyword. Similarly, any Ruby API that takes advantage of class level declarations could add these to the documentation in a very explicit format by treating them as first- class objects in any outputted documentation.
Generally, a handler class will declare a set of statements which it will handle using the {handles} class declaration. It will then implement the {process} method to do the work. The processing would usually involve the manipulation of the {namespace}, {owner} {CodeObjects::Base code objects} or the creation of new ones, in which case they should be registered by {register}, a method that sets some basic attributes for the new objects.
Handlers are usually simple and take up to a page of code to process and register a new object or add new attributes to the current namespace.
A Handler is automatically registered when it is subclassed from the base class. The only other thing that needs to be done is to specify which statement the handler will process. This is done with the handles declaration, taking either a {Parser::Ruby::Legacy::RubyToken}, {String} or `Regexp`. Here is a simple example which processes module statements.
class MyModuleHandler < YARD::Handlers::Base handles TkMODULE def process # do something end end
The goal of a specific handler is really up to the developer, and as such there is no real guideline on how to process the data. However, it is important to know where the data is coming from to be able to use it.
The statement attribute pertains to the {Parser::Ruby::Legacy::Statement} object containing a set of tokens parsed in by the parser. This is the main set of data to be analyzed and processed. The comments attached to the statement can be accessed by the {Parser::Ruby::Legacy::Statement#comments} method, but generally the data to be processed will live in the tokens attribute. This list can be converted to a String using #to_s to parse the data with regular expressions (or other text processing mechanisms), if needed.
The namespace attribute is a {CodeObjects::NamespaceObject namespace object} which represents the current namespace that the parser is in. For instance:
module SomeModule class MyClass def mymethod; end end end
If a handler was to parse the 'class MyClass' statement, it would be necessary to know that it belonged inside the SomeModule module. This is the value that namespace would return when processing such a statement. If the class was then entered and another handler was called on the method, the namespace would be set to the 'MyClass' code object.
The owner attribute is similar to the namespace attribute in that it also follows the scope of the code during parsing. However, a namespace object is loosely defined as a module or class and YARD has the ability to parse beyond module and class blocks (inside methods, for instance), so the owner attribute would not be limited to modules and classes.
To put this into context, the example from above will be used. If a method handler was added to the mix and decided to parse inside the method body, the owner would be set to the method object but the namespace would remain set to the class. This would allow the developer to process any method definitions set inside a method (def x; def y; 2 end end) by adding them to the correct namespace (the class, not the method).
In summary, the distinction between namespace and owner can be thought of as the difference between first-class Ruby objects (namespaces) and second-class Ruby objects (methods).
Mainly needed for parsing methods, the visibility and scope attributes refer to the public/protected/private and class/instance values (respectively) of the current parsing position.
In addition to parsing a statement and creating new objects, some handlers may wish to continue parsing the code inside the statement's block (if there is one). In this context, a block means the inside of any statement, be it class definition, module definition, if statement or classic 'Ruby block'.
For example, a class statement would be "class MyClass" and the block would be a list of statements including the method definitions inside the class. For a class handler, the programmer would execute the {parse_block} method to continue parsing code inside the block, with the namespace now pointing to the class object the handler created.
YARD has the ability to continue into any block: class, module, method, even if statements. For this reason, the block parsing method must be invoked explicitly out of efficiency sake.
@abstract Subclass this class to provide a handler for YARD to use
during the processing phase.
@see CodeObjects::Base @see CodeObjects::NamespaceObject @see handles @see namespace @see owner @see register @see parse_block
Clear all registered subclasses. Testing purposes only @return [void]
# File lib/yard/handlers/base.rb, line 152 def clear_subclasses @@subclasses = [] end
@return [Array] a list of matchers for the handler object. @see handles?
# File lib/yard/handlers/base.rb, line 204 def handlers @handlers ||= [] end
Declares the statement type which will be processed by this handler.
A match need not be unique to a handler. Multiple handlers can process the same statement. However, in this case, care should be taken to make sure that {parse_block} would only be executed by one of the handlers, otherwise the same code will be parsed multiple times and slow YARD down.
@param [Parser::RubyToken, Symbol, String, Regexp] matches
statements that match the declaration will be processed by this handler. A {String} match is equivalent to a +/\Astring/+ regular expression (match from the beginning of the line), and all token matches match only the first token of the statement.
# File lib/yard/handlers/base.rb, line 185 def handles(*matches) (@handlers ||= []).push(*matches) end
This class is implemented by {Ruby::Base} and {Ruby::Legacy::Base}. To implement a base handler class for another language, implement this method to return true if the handler should process the given statement object. Use {handlers} to enumerate the matchers declared for the handler class.
@param statement a statement object or node (depends on language type) @return [Boolean] whether or not this handler object should process
the given statement
# File lib/yard/handlers/base.rb, line 198 def handles?(statement) raise NotImplementedError, "override #handles? in a subclass" end
Declares that a handler should only be called when inside a filename by its basename or a regex match for the full path.
@param [String, Regexp] filename a matching filename or regex @return [void] @since 0.6.2
# File lib/yard/handlers/base.rb, line 228 def in_file(filename) (@in_files ||= []) << filename end
# File lib/yard/handlers/base.rb, line 162 def inherited(subclass) @@subclasses ||= [] @@subclasses << subclass end
@return [Boolean] whether the filename matches the declared file
match for a handler. If no file match is specified, returns true.
@since 0.6.2
# File lib/yard/handlers/base.rb, line 235 def matches_file?(filename) @in_files ||= nil # avoid ruby warnings return true unless @in_files @in_files.any? do |in_file| case in_file when String File.basename(filename) == in_file when Regexp filename =~ in_file else true end end end
Declares that the handler should only be called when inside a {CodeObjects::NamespaceObject}, not a method body.
@return [void]
# File lib/yard/handlers/base.rb, line 212 def namespace_only @namespace_only = true end
@return [Boolean] whether the handler should only be processed inside
a namespace.
# File lib/yard/handlers/base.rb, line 218 def namespace_only? (@namespace_only ||= false) ? true : false end
# File lib/yard/handlers/base.rb, line 269 def initialize(source_parser, stmt) @parser = source_parser @statement = stmt end
Generates a process method, equivalent to +def process; ... end+. Blocks defined with this syntax will be wrapped inside an anonymous module so that the handler class can be extended with mixins that override the process method without alias chaining.
@!macro yard.handlers.process
@!method process Main processing callback @return [void]
@see process @return [void] @since 0.5.4
# File lib/yard/handlers/base.rb, line 262 def process(&block) mod = Module.new mod.send(:define_method, :process, &block) include mod end
Returns all registered handler subclasses. @return [Array<Base>] a list of handlers
# File lib/yard/handlers/base.rb, line 158 def subclasses @@subclasses ||= [] end
@abstract Implement this method to return the parameters in a method call
statement. It should return an empty list if the statement is not a method call.
@return [Array<String>] a list of argument names
# File lib/yard/handlers/base.rb, line 567 def call_params raise NotImplementedError end
@abstract Implement this method to return the method being called in
a method call. It should return nil if the statement is not a method call.
@return [String] the method name being called @return [nil] if the statement is not a method call
# File lib/yard/handlers/base.rb, line 576 def caller_method raise NotImplementedError end
Ensures that a specific object has been parsed and loaded into the registry. This is necessary when adding data to a namespace, for instance, since the namespace may not have been processed yet (it can be located in a file that has not been handled).
Calling this method defers the handler until all other files have been processed. If the object gets resolved, the rest of the handler continues, otherwise an exception is raised.
@example Adding a mixin to the String class programmatically
ensure_loaded! P('String') # "String" is now guaranteed to be loaded P('String').mixins << P('MyMixin')
@param [Proxy, CodeObjects::Base] object the object to resolve. @param [Integer] max_retries the number of times to defer the handler
before raising a +NamespaceMissingError+.
@raise [NamespaceMissingError] if the object is not resolved within
+max_retries+ attempts, this exception is raised and the handler finishes processing.
# File lib/yard/handlers/base.rb, line 544 def ensure_loaded!(object, max_retries = 1) return if object.root? return object unless object.is_a?(Proxy) retries = 0 while object.is_a?(Proxy) if retries <= max_retries log.debug "Missing object #{object} in file `#{parser.file}', moving it to the back of the line." parser.parse_remaining_files else raise NamespaceMissingError, object end retries += 1 end object end
# File lib/yard/handlers/base.rb, line 335 def namespace=(v); parser.namespace=(v) end
# File lib/yard/handlers/base.rb, line 333 def owner=(v) parser.owner=(v) end
Parses the semantic "block" contained in the statement node.
@abstract Subclasses should call {Processor#process parser.process}
# File lib/yard/handlers/base.rb, line 297 def parse_block(*args) raise NotImplementedError, "#{self} did not implement a #parse_block method for handling" end
The main handler method called by the parser on a statement that matches the {handles} declaration.
Subclasses should override this method to provide the handling functionality for the class.
@return [Array<CodeObjects::Base>, CodeObjects::Base, Object]
If this method returns a code object (or a list of them), they are passed to the +#register+ method which adds basic attributes. It is not necessary to return any objects and in some cases you may want to explicitly avoid the returning of any objects for post-processing by the register method.
@see handles @see register
# File lib/yard/handlers/base.rb, line 290 def process raise NotImplementedError, "#{self} did not implement a #process method for handling." end
Executes a given block with specific state values for {owner}, {namespace} and {scope}.
@param [Proc] block the block to execute with specific state @option opts [CodeObjects::NamespaceObject] :namespace (value of namespace)
the namespace object that {#namespace} will be equal to for the duration of the block.
@option opts [Symbol] :scope (:instance)
the scope for the duration of the block.
@option opts [CodeObjects::Base] :owner (value of owner)
the owner object (method) for the duration of the block
@yield a block to execute with the given state values.
# File lib/yard/handlers/base.rb, line 355 def push_state(opts = {}, &block) opts = { :namespace => namespace, :scope => :instance, :owner => owner || namespace, :visibility => nil }.update(opts) ns, vis, sc, oo = namespace, visibility, scope, owner self.namespace = opts[:namespace] self.visibility = opts[:visibility] || :public self.scope = opts[:scope] self.owner = opts[:owner] yield self.namespace = ns self.visibility = vis self.scope = sc self.owner = oo end
Do some post processing on a list of code objects. Adds basic attributes to the list of objects like the filename, line number, {CodeObjects::Base#dynamic}, source code and {CodeObjects::Base#docstring}, but only if they don't exist.
@param [Array<CodeObjects::Base>] objects
the list of objects to post-process.
@return [CodeObjects::Base, Array<CodeObjects::Base>]
returns whatever is passed in, for chainability.
# File lib/yard/handlers/base.rb, line 389 def register(*objects) objects.flatten.each do |object| next unless object.is_a?(CodeObjects::Base) register_ensure_loaded(object) yield(object) if block_given? register_file_info(object) register_source(object) register_visibility(object) register_docstring(object) register_group(object) register_dynamic(object) register_module_function(object) end objects.size == 1 ? objects.first : objects end
Registers any docstring found for the object and expands macros
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 433 def register_docstring(object, docstring = statement.comments, stmt = statement) docstring = docstring.join("\n") if Array === docstring parser = Docstring.parser parser.parse(docstring || "", object, self) if object && docstring object.docstring = parser.to_docstring # Add hash_flag/line_range if stmt object.docstring.hash_flag = stmt.comments_hash_flag object.docstring.line_range = stmt.comments_range end end register_transitive_tags(object) end
Registers the object as dynamic if the object is defined inside a method or block (owner != namespace)
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 520 def register_dynamic(object) object.dynamic = true if owner != namespace end
Ensures that the object's namespace is loaded before attaching it to the namespace.
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 411 def register_ensure_loaded(object) begin ensure_loaded!(object.namespace) object.namespace.children << object rescue NamespaceMissingError end end
Registers the file/line of the declaration with the object
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 424 def register_file_info(object, file = parser.file, line = statement.line, comments = statement.comments) object.add_file(file, line, comments) end
Registers the object as being inside a specific group
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 456 def register_group(object, group = extra_state.group) if group unless object.namespace.is_a?(Proxy) object.namespace.groups |= [group] end object.group = group end end
Registers the same method information on the module function, if the object was defined as a module function.
@param [CodeObjects::Base] object the possible module function object
to copy data for
@since 0.8.0
# File lib/yard/handlers/base.rb, line 506 def register_module_function(object) return unless object.is_a?(MethodObject) return unless object.module_function? modobj = MethodObject.new(object.namespace, object.name) object.copy_to(modobj) modobj.visibility = :private end
@param [CodeObjects::Base] object the object to register @return [void] @since 0.8.0
# File lib/yard/handlers/base.rb, line 483 def register_source(object, source = statement, type = parser.parser_type) return unless object.is_a?(MethodObject) object.source ||= source object.source_type = type end
Registers visibility on a method object. If the object does not respond to setting visibility, nothing is done.
@param [visibility=] object the object to register @param [Symbol] visibility the visibility to set on the object @since 0.8.0
# File lib/yard/handlers/base.rb, line 495 def register_visibility(object, visibility = self.visibility) return unless object.respond_to?(:visibility=) object.visibility = visibility end
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