Introduction
ParseTree includes a useful class called SexpProcessor. SexpProcessor allows you to write very clean ruby language tools that focus on what you are interested in, and ignore the rest. Below is a very basic dependency analyzer. It records references to classes, and the method it was referenced from and outputs a simple report.
It doesn’t do too much, but you can’t expect too much in 60 lines of ruby (including empty lines)! However with a little effort, you can make this into a truly useful ruby analysis tool.
Read the code, an explanation is further below.
The Code, with walkthrough…
Most of the code is rather boring, I’ll only make note of the interesting or potentially confusing parts.
#!/usr/local/bin/ruby -w
old_classes = [] new_classes = []
require ‘parse_tree’ require ‘sexp_processor’
| ObjectSpace.each_object(Module) { | klass | old_classes « klass } |
class DependencyAnalyzer < SexpProcessor
attr_reader :dependencies
attr_accessor :current_class
def initialize
super
self.auto_shift_type = true
@dependencies = Hash.new { |h,k| h[k] = [] }
@current_method = nil
@current_class = nil
end
This is the front-end for the whole script. It grabs the parse tree for each class specified and runs it through DependencyAnalyzer. Once everything is run through, it iterates through the results and prints a simple report (shown below).
def self.process(*klasses)
analyzer = self.new
klasses.each do |start_klass|
analyzer.current_class = start_klass
analyzer.process(ParseTree.new.parse_tree(start_klass))
end
deps = analyzer.dependencies
deps.keys.sort.each do |dep_to|
dep_from = deps[dep_to]
puts "#{dep_to} referenced by:\n #{dep_from.uniq.sort.join("\n ")}"
end
end
A :defn node is the top level node for a method definition. It consists of a name, argument list, and a body. We simply grab the name and record it for accounting purposes in the :const processor.
def process_defn(exp)
name = exp.shift
@current_method = name
return s(:defn, name, process(exp.shift), process(exp.shift))
end
A :const node simply specifies what const to access. In some cases it is a class and in others it is a regular const at the global or module scope. We ask Object to do a const_get and figure out if it really is a class or not. If it is, we add it to the dependency list.
def process_const(exp)
name = exp.shift
const = "#{@current_class}.#{@current_method}"
is_class = ! (Object.const_get(name) rescue nil).nil?
@dependencies[name] << const if is_class
return s(:const, name)
end end
Finally, we require all the files specified on the command-line, find all the new classes introduced, and then tell DependencyAnalyzer to process them.
if FILE == $0 then ARGV.each { |name| require name } ObjectSpace.each_object(Module) { |klass| new_classes « klass } DependencyAnalyzer.process(*(new_classes - old_classes)) end
Details
SexpProcessor Basics
SexpProcessor has one basic method in it, process. That method takes a sexp and generally returns a sexp. Internally, it looks at the type of node it is currently processing, and either generically processes it, or finds a custom processor that is implemented in a subclass and dispatches to it. In the example above, process_const and process_defn are examples of custom processors.
There are more features to process, but that is pretty much it for basic usage. Read the code if you’d like, it isn’t large (about 300 lines).
DependencyAnalyzer Details
In short, process_defn simply records the current method name, and process_const records all constant accesses. It just so happens that all class and module references are actually const references. Finally DependencyAnalyzer.process hooks everything together and then prints a readable report when done.
Not much eh? That is a good thing in my opinion. It means that in 60 lines you can make a quick and dirty tool. Imagine what you can do in 300 lines…
Example Output
Let’s run our dependency analyzer against ruby2c, the real motivation behind the ParseTree framework:
% ./deps.rb rewriter support ruby_to_c type_checker typed_sexp_processor ArgumentError referenced by: CompositeSexpProcessor.« Array referenced by: RubyToC.process_if Type.unify Fixnum referenced by: TypeChecker.process_lit Object referenced by: DependencyAnalyzer.process_const PP referenced by: PP::ObjectMixin.pretty_print_inspect PP::PPMethods.pp Sexp referenced by: Rewriter.process_call (6 other Rewriter.process* methods) TypedSexp.sexp_types SexpProcessor referenced by: CompositeSexpProcessor.« Symbol referenced by: PP::PPMethods.pp_object Thread referenced by: PP::PPMethods.guard_inspect_key PP::PPMethods.pp Type referenced by: RubyToC.process_call TypeChecker.bootstrap (24 other TypeChecker.process* methods) TypeError referenced by: FunctionType.unify_components Type.unify TypedSexp referenced by: R2CRewriter.process_call TypedSexp.==
Unadulterated Code
This code will also be included in the next release of ParseTree.
#!/usr/local/bin/ruby -w
old_classes = []; new_classes = []
require ‘pp’ require ‘parse_tree’ require ‘sexp_processor’
| ObjectSpace.each_object(Module) { | klass | old_classes « klass } |
class DependencyAnalyzer < SexpProcessor
attr_reader :dependencies
attr_accessor :current_class
def initialize
super
self.auto_shift_type = true
@dependencies = Hash.new { |h,k| h[k] = [] }
@current_method = nil
@current_class = nil
end
def self.process(*klasses)
analyzer = self.new
klasses.each do |start_klass|
analyzer.current_class = start_klass
analyzer.process(ParseTree.new.parse_tree(start_klass))
end
deps = analyzer.dependencies
deps.keys.sort.each do |dep_to|
dep_from = deps[dep_to]
puts "#{dep_to} referenced by:\n #{dep_from.uniq.sort.join("\n ")}"
end
end
def process_defn(exp)
name = exp.shift
@current_method = name
return s(:defn, name, process(exp.shift), process(exp.shift))
end
def process_const(exp)
name = exp.shift
const = "#{@current_class}.#{@current_method}"
is_class = ! (Object.const_get(name) rescue nil).nil?
@dependencies[name] << const if is_class
return s(:const, name)
end end
if FILE == $0 then ARGV.each { |name| require name } ObjectSpace.each_object(Module) { |klass| new_classes « klass } DependencyAnalyzer.process(*(new_classes - old_classes)) end