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@chrisarcand
Deletion Driven
Development:
Code to delete code!
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Chris Arcand
chrisarcand
chrisarcand
www.chrisarcand.com
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MINNESOTA
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MINNESOTA
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MINNESOTA
Minneapolis
St. Paul
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@chrisarcand chrisarcand.com
I
PROGRAMMING
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@chrisarcand chrisarcand.com
I
WRITING
CODE
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@chrisarcand chrisarcand.com
However…
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@chrisarcand chrisarcand.com
I
DELETING
CODE
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@chrisarcand chrisarcand.com
• Over-engineering
Previous developer adding “potentially helpful” methods
• Poorly written code
Super-specific, single edge case methods
• Refactoring, deprecations
Callers get refactored over time and methods eventually
aren’t needed anymore
• etc, etc
Dead code? How?
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@chrisarcand chrisarcand.com
“Who cares?”
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@chrisarcand chrisarcand.com
“Deleting Code” (2002)
Ned Batchelder
http://nedbatchelder.com/text/deleting-code.html
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@chrisarcand chrisarcand.com
If you have a chunk of code you don't need
any more, there's one big reason to delete it
for real rather than leaving it in a disabled
state: To reduce noise and uncertainty.
Some of the worst enemies a developer has
are noise or uncertainty in his code,
because they prevent him from working with
it effectively in the future.
“
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@chrisarcand chrisarcand.com
What if we could programmatically
find unused code to delete?
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@chrisarcand chrisarcand.com
Ruby code (.rb)
? ? ?
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@chrisarcand chrisarcand.com
Part I: Parsing the code
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@chrisarcand chrisarcand.com
Do you understand the following
sequences of characters?
How do you know?
Modified examples and grammar from Robert B. Heckendorn, University of Idaho
http://marvin.cs.uidaho.edu/Teaching/CS445/grammar.html
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@chrisarcand chrisarcand.com
“The boy owns a dog.”
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@chrisarcand chrisarcand.com
“The dog loves the boy.”
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“Loves boy the.”
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@chrisarcand chrisarcand.com
How could you programmatically determine
which of those are correct…
…and which are not?
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@chrisarcand chrisarcand.com
✨Context-free Grammar✨
(CFG)
A set of production rules that describe all possible
strings in a given formal language.
“What sentences are in the language
and what are not?”
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@chrisarcand chrisarcand.com
✨Backus-Naur Form✨
(BNF)
One of two main notation techniques for context-
free grammars, often used to describe computer
programming languages.
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
Symbols
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
< non-terminals >
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
TERMINALS
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
Symbol on left is replaced with expression on the right
‘OR’ (choose between expressions)
‘definitional operator’
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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@chrisarcand chrisarcand.com
::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
Terminal found
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
Terminal found
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES | BITES
The boy owns a dog.
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The boy owns a dog.
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THE BOY OWNS
A DOG
Parsing was successful!
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“The dog loves the boy.”
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THE DOG LOVES
THE BOY
Parsing was successful!
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Loves boy the.
“ ”
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::=
::=
::=
::=
::= THE | A
::= BOY | DOG
::= OWNS | LOVES
Loves boy the.
???
???
???
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“The boy owns a dog.”
“The dog loves the boy.”
“Loves boy the.”
In programming terms…
OK
OK
SYNTAX ERROR
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@chrisarcand chrisarcand.com
How does Ruby know the
meaning of these characters?
class Person
def initialize(name)
@name = name
end
def say_hello
puts “Hi! My name is #{@name}!”
end
end
chris = Person.new(“Chris”)
chris.say_hello
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Figure 1-13, Ruby Under a Microscope by Pat Shaughnessy
Used with permission
How Ruby tokenizes and parses code
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Figure 1-13, Ruby Under a Microscope by Pat Shaughnessy
Used with permission
How Ruby tokenizes and parses code
Ruby uses a LALR parser generator called Bison
Look-Ahead, Left, Reversed Rightmost Derivation
LALR(k): k refers to the amount of look-ahead
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Figure 1-13, Ruby Under a Microscope by Pat Shaughnessy
Used with permission
How Ruby tokenizes and parses code
Ruby uses a LALR parser generator called Bison
Look-Ahead, Left, Reversed Rightmost Derivation
LALR(k): k refers to the amount of look-ahead
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Racc
https://github.com/tenderlove/racc
An LALR(1) parser generator
How we will tokenize and parse code
ruby_parser
https://github.com/seattlerb/ruby_parser
A Ruby parser, written in Ruby, using racc
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class Person
def greet(name)
puts "Hello #{name}!"
end
end
person = Person.new
person.greet("RubyKaigi")
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class Person
def greet(name)
puts "Hello #{name}!"
end
end
person = Person.new
person.greet("RubyKaigi")
> parser = RubyParser.for_current_ruby
> parser.parse(File.read(“example1.rb”))
1 s(:block,
2 s(:class, :Person, nil,
3 s(:defn, :greet, s(:args, :name),
4 s(:call, nil, :puts,
5 s(:dstr, "Hello ", s(:evstr, s(:lvar, :name)), s(:str, "!"))))),
6 s(:lasgn, :person, s(:call, s(:const, :Person), :new)),
7 s(:call, s(:lvar, :person), :greet, s(:str, "RubyKaigi")))
example1.rb
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1 s(:block,
2 s(:class, :Person, nil,
3 s(:defn, :greet, s(:args, :name),
4 s(:call, nil, :puts,
5 s(:dstr, "Hello ", s(:evstr, …
6 s(:lasgn, :person, s(:call, …
7 s(:call, s(:lvar, :person), :greet, …
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ruby_parser
racc
Ruby code (.rb)
Ruby23Parser
Parsing
Generic processing
File.read()
s-expression (parse tree)
? ? ?
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Part II: Processing the s-expression
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class MinimalSexpProcessor
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def initialize
@processors ={}
public_methods.each do |name|
case name
when /^process_(.*)/ then
@processors[$1.to_sym] = name.to_sym
end
end
end
end
class MinimalSexpProcessor
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process_defn
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process_defn
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process_defn
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defn =>:process_defn
:
@processors = {
}
Node type Corresponding
processor
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def process(exp)
return nil if exp.nil?
type = exp.first
meth = @processors[type] || default_method
return nil unless meth
if meth == default_method && warn_on_default
puts "WARNING: Using default method #{meth} for #{type}"
end
self.send(meth, exp) if meth
end
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class MinimalSexpProcessor
attr_accessor :default_method
attr_accessor :warn_on_default
def initialize
@default_method = nil
@warn_on_default = true
@processors ={}
public_methods.each do |name|
case name
when /^process_(.*)/ then
@processors[$1.to_sym] = name.to_sym
end
end
end
end
def process(exp)
return nil if exp.nil?
type = exp.first
meth = @processors[type] || default_method
return nil unless meth
if meth == default_method && warn_on_default
puts "WARNING: Using default method #{meth} for #{type}"
end
self.send(meth, exp) if meth
end
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class MinimalSexpProcessor
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class SillyProcessor < MinimalSexpProcessor
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def process_defn(exp)
method_name = exp[1]
puts "PROCESSING A METHOD DEFINITION NODE: #{method_name}"
process_until_empty(exp)
s()
end
def process_not_defn(exp)
node_type = exp[0]
puts "Processing node: #{node_type}"
process_until_empty(exp)
s()
end
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def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
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def initialize
super
@default_method = :process_not_defn
@warn_on_default = false
end
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class SillyProcessor < MinimalSexpProcessor
def process_defn(exp)
method_name = exp[1]
puts "PROCESSING A METHOD DEFINITION NODE: #{method_name}"
process_until_empty(exp)
s()
end
def process_not_defn(exp)
node_type = exp[0]
puts "Processing node: #{node_type}"
process_until_empty(exp)
s()
end
def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
end
def initialize
super
@default_method = :process_not_defn
@warn_on_default = false
end
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1 require 'ruby_parser'
2 require_relative 'minimal_sexp_processor.rb'
3 require_relative 'silly_processor.rb'
4
5 parser = RubyParser.for_current_ruby
6 file = File.read(ARGV[0])
7 sexp = parser.parse(file)
8
9 processor = SillyProcessor.new
10 processor.process(sexp)
silly_processor_demo.rb
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$ ruby minimal_parser_demo.rb example1.rb
Processing node: block
Processing node: class
PROCESSING A METHOD DEFINITION NODE: greet
Processing node: args
Processing node: call
Processing node: dstr
Processing node: evstr
Processing node: lvar
Processing node: str
Processing node: lasgn
Processing node: call
Processing node: const
Processing node: call
Processing node: lvar
Processing node: str
1 class Person
2 def greet(name)
3 puts "Hello #{name}!"
4 end
5 end
6
7 person = Person.new
8 person.greet("RubyKaigi")
example1.rb
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class MethodTrackingProcessor < MinimalSexpProcessor
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class MethodTrackingProcessor < MinimalSexpProcessor
attr_reader :method_locations
def initialize
super
@default_method = :process_until_empty
@warn_on_default = false
@class_stack = []
@method_stack = []
@method_locations = {}
end
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class MethodTrackingProcessor < MinimalSexpProcessor
attr_reader :method_locations
def initialize
super
@default_method = :process_until_empty
@warn_on_default = false
@class_stack = []
@method_stack = []
@method_locations = {}
end
def process_defn(exp)
exp.shift # node type
name = exp.shift
in_method(name, exp.file, exp.line) do
process_until_empty(exp)
end
s()
end
def process_class(exp)
exp.shift # node type
in_klass(exp.shift) do
process_until_empty(exp)
end
s()
end
def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
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class MethodTrackingProcessor < MinimalSexpProcessor
attr_reader :method_locations
def initialize
super
@default_method = :process_until_empty
@warn_on_default = false
@class_stack = []
@method_stack = []
@method_locations = {}
end
def process_defn(exp)
exp.shift # node type
name = exp.shift
in_method(name, exp.file, exp.line) do
process_until_empty(exp)
end
s()
end
def process_class(exp)
exp.shift # node type
in_klass(exp.shift) do
process_until_empty(exp)
end
s()
end
def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
def in_method(name, file, line)
method_name = Regexp === name ? name.inspect : name.to_s
@method_stack.unshift(method_name)
@method_locations[signature] = "#{file}:#{line}"
yield
ensure
@method_stack.shift
end
def in_klass(name)
@class_stack.unshift(name)
with_new_method_stack do
yield
end
ensure
@class_stack.shift
end
def with_new_method_stack
old_method_stack, @method_stack = @method_stack, []
yield
ensure
@method_stack = old_method_stack
end
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class MethodTrackingProcessor < MinimalSexpProcessor
attr_reader :method_locations
def initialize
super
@default_method = :process_until_empty
@warn_on_default = false
@class_stack = []
@method_stack = []
@method_locations = {}
end
def process_defn(exp)
exp.shift # node type
name = exp.shift
in_method(name, exp.file, exp.line) do
process_until_empty(exp)
end
s()
end
def process_class(exp)
exp.shift # node type
in_klass(exp.shift) do
process_until_empty(exp)
end
s()
end
def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
def in_method(name, file, line)
method_name = Regexp === name ? name.inspect : name.to_s
@method_stack.unshift(method_name)
@method_locations[signature] = "#{file}:#{line}"
yield
ensure
@method_stack.shift
end
def in_klass(name)
@class_stack.unshift(name)
with_new_method_stack do
yield
end
ensure
@class_stack.shift
end
def with_new_method_stack
old_method_stack, @method_stack = @method_stack, []
yield
ensure
@method_stack = old_method_stack
end
def klass_name
@class_stack.first
end
def method_name
@method_stack.first
end
def signature
"#{klass_name}##{method_name}"
end
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class MethodTrackingProcessor < MinimalSexpProcessor
attr_reader :method_locations
def initialize
super
@default_method = :process_until_empty
@warn_on_default = false
@class_stack = []
@method_stack = []
@method_locations = {}
end
def process_defn(exp)
exp.shift # node type
name = exp.shift
in_method(name, exp.file, exp.line) do
process_until_empty(exp)
end
s()
end
def process_class(exp)
exp.shift # node type
in_klass(exp.shift) do
process_until_empty(exp)
end
s()
end
def process_until_empty(exp)
until exp.empty?
sexp = exp.shift
process(sexp) if Sexp === sexp
end
end
def in_method(name, file, line)
method_name = Regexp === name ? name.inspect : name.to_s
@method_stack.unshift(method_name)
@method_locations[signature] = "#{file}:#{line}"
yield
ensure
@method_stack.shift
end
def in_klass(name)
@class_stack.unshift(name)
with_new_method_stack do
yield
end
ensure
@class_stack.shift
end
def with_new_method_stack
old_method_stack, @method_stack = @method_stack, []
yield
ensure
@method_stack = old_method_stack
end
def klass_name
@class_stack.first
end
def method_name
@method_stack.first
end
def signature
"#{klass_name}##{method_name}"
end
end
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1 class Person
2 def greet(name)
3 puts "Hello #{name}!"
4 end
5
6 def say_goodbye(name)
7 puts "Goodbye, #{name}!"
8 end
9 end
10
11 class Dog
12 def bark!
13 puts "Woof!"
14 end
15 end
16
17 person = Person.new
18 person.greet("RubyKaigi")
example2.rb
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5 path = ARGV[0]
6 file = File.read(path)
7 sexp = RubyParser.for_current_ruby.process(file, path)
8
9 processor = MethodTrackingProcessor.new
10 processor.process(sexp)
11 pp processor.method_locations
method_tracking_demo.rb
$ ruby minimal_parser_demo.rb example2.rb
{ "Person#greet" => "example2.rb:2",
"Person#say_goodbye" => "example2.rb:6",
“Dog#bark!" => "example2.rb:12" }
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ruby_parser
racc
Ruby code (.rb)
Ruby23Parser
MethodTrackingProcessor
MinimalSexpProcessor
Parsing
Generic processing
File.read()
s-expression (parse tree)
Call processing and reporting
? ? ?
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Part III: Building the dead method finder
(or, drawing the rest of the damn owl)
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ruby_parser
racc
Ruby code (.rb)
Ruby23Parser
Parsing
Generic processing
File.read()
s-expression (parse tree)
Call processing and reporting
Our tool DeadMethodFinder
MethodTrackingProcessor
MinimalSexpProcessor
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class DeadMethodFinder < MethodTrackingProcessor
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class DeadMethodFinder < MethodTrackingProcessor
attr_reader :known
attr_reader :called
def initialize
super
@known = Hash.new { |h,k| h[k] = Set.new }
@called = Set.new
end
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class DeadMethodFinder < MethodTrackingProcessor
attr_reader :known
attr_reader :called
def initialize
super
@known = Hash.new { |h,k| h[k] = Set.new }
@called = Set.new
end
def process_defn(exp)
super do
known[plain_method_name] << klass_name
process_until_empty(exp)
end
end
def process_call(exp)
method_name = exp[2]
called << method_name
process_until_empty(exp)
exp
end
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class DeadMethodFinder < MethodTrackingProcessor
attr_reader :known
attr_reader :called
def initialize
super
@known = Hash.new { |h,k| h[k] = Set.new }
@called = Set.new
end
def process_defn(exp)
super do
known[plain_method_name] << klass_name
process_until_empty(exp)
end
end
def process_call(exp)
method_name = exp[2]
called << method_name
process_until_empty(exp)
exp
end
def uncalled
not_called = known.keys - called.to_a
by_class = Hash.new { |h,k| h[k] = [] }
not_called.each do |meth|
known[meth].each do |klass|
by_class[klass] << meth
end
end
by_class
end
# #method_name -> :method_name
def plain_method_name
method_name.to_s.sub(/^::|#/, "").to_sym
end
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class DeadMethodFinder < MethodTrackingProcessor
attr_reader :known
attr_reader :called
def initialize
super
@known = Hash.new { |h,k| h[k] = Set.new }
@called = Set.new
end
def process_defn(exp)
super do
known[plain_method_name] << klass_name
process_until_empty(exp)
end
end
def process_call(exp)
method_name = exp[2]
called << method_name
process_until_empty(exp)
exp
end
def uncalled
not_called = known.keys - called.to_a
by_class = Hash.new { |h,k| h[k] = [] }
not_called.each do |meth|
known[meth].each do |klass|
by_class[klass] << meth
end
end
by_class
end
# #method_name -> :method_name
def plain_method_name
method_name.to_s.sub(/^::|#/, "").to_sym
end
end
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
example3.rb
=> Hello RubyKaigi!
Bark!
Ahhh…
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
example3.rb
> processor = DeadMethodFinder.new
> processor.process(sexp)
> puts processor.uncalled
=> {"Person"=>[:say_goodbye], "Dog"=>[:pet]}
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s(:call, s(:lvar, :dog), :send, s(:lit, :pet))
dog.send(:pet)
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def process_call(exp)
method_name = exp[2]
case method_name
when :send, :public_send, :__send__
msg_arg = exp[3]
if Sexp === msg_arg && [:lit, :str].include?(msg_arg.sexp_type)
called << msg_arg.last.to_sym
end
end
called << method_name
process_until_empty(exp)
exp
end
s(:call, s(:lvar, :dog), :send, s(:lit, :pet))
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
example3.rb
> processor = DeadMethodFinder.new
> processor.process(sexp)
> puts processor.uncalled
=> {"Person"=>[:say_goodbye]}
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s(:call, nil, :attr_accessor, s(:lit, :fed))
attr_accessor :fed
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s(:call, nil, :attr_accessor, s(:lit, :fed))
def process_call(exp)
method_name = exp[2]
case method_name
when :attr_accessor
_, _, _, *args = exp
file, line = exp.file, exp.line
args.each do |(_, name)|
record_known_method(name, file, line)
record_known_method("#{name}=".to_sym, file, line)
end
when :send, :public_send, :__send__
_, _, _, msg_arg, * = exp
if Sexp === msg_arg && [:lit, :str].include?(msg_arg.sexp_type)
called << msg_arg.last.to_sym
end
end
called << method_name
process_until_empty(exp)
exp
end
def record_known_method(name, file, line)
signature = "#{klass_name}##{name}"
method_locations[signature] = "#{file}:#{line}"
known[name] << klass_name
end
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def report
puts "These methods MIGHT not be called:"
uncalled.each do |klass, methods|
not_called_methods = methods.map do |method|
location = method_locations["#{klass}##{method}"]
" %-35s %s" % [method, location]
end
not_called_methods.compact!
next if not_called_methods.empty?
puts "\n#{klass}"
puts not_called_methods.join "\n"
end
end
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> processor = DeadMethodFinder.new
> processor.process(sexp)
> processor.report
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
example2.rb
These methods MIGHT not be called:
Person
say_goodbye example2.rb:7
Dog
fed example2.rb:21
fed= example2.rb:21
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6
7
8
9
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
# Never used
def say_goodbye(name)
speak "Goodbye, #{name}!"
end
attr_accessor :fed # Never used
-
-
-
-
-
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✌
Done?
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Done
Ruby is complex (to parse)
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Done?
Ruby is complex (to parse)
…but adding edge cases is easy.
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reuben.fed = true
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
39
example4.rb
Person
say_goodbye example2.rb:7
Dog
fed example2.rb:21
fed= example2.rb:21
reuben.fed = true
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Brought to you by: Julian Cheal
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s(:attrasgn, s(:lvar, :reuben), :fed=, s(:true))
def process_attrasgn(exp)
method_name = exp[2]
method_name = method_name.last if Sexp === method_name
called << method_name
process_until_empty exp
exp
end
reuben.fed = true
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1 class Person
2 def greet(name)
3 speak "Hello #{name}!"
4 end
5
6 # Never used
7 def say_goodbye(name)
8 speak "Goodbye, #{name}!"
9 end
10
11 def speak(text)
12 puts text
13 end
14
15 def pet_dog(dog)
16 dog.send(:pet)
17 end
18 end
19
20 class Dog
21 attr_accessor :fed # Never used
22
23 def bark!
24 puts "Bark!"
25 end
26
27 def pet
28 puts "Ahhh..."
29 end
30 end
31
32
33 chris = Person.new
34 reuben = Dog.new
35
36 chris.greet("RubyKaigi")
37 reuben.bark!
38 chris.pet_dog(reuben)
39 reuben.fed = true
example4.rb
Person
say_goodbye example2.rb:7
Dog
fed example2.rb:21
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What about Rails DSL?
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:after_commit
:before_create
:after_create
:before_destroy
:before_filter
:before_action
:after_validation
:before_update
:around_save
:validates
:validates_length_of
:validates_format_of
:validates_cuteness_of
:validates_confirmation_of
:validate
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:after_commit
:before_create
:after_create
:before_destroy
:before_filter
:before_action
:after_validation
:before_update
:around_save
:validates
:validates_length_of
:validates_format_of
:validates_cuteness_of
:validates_confirmation_of
:validate
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What about my own DSL?
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class Disk < ActiveRecord::Base
has_many :partitions
virtual_column :allocated_space,
type: :integer,
uses: :partitions
virtual_column :used_percent_of_provisioned,
type: :float
virtual_has_many :storage_systems,
class_name: "CimComputerSystem"
def allocated_space
# ...
end
def used_percent_of_provisioned
# ...
end
end
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RAILS_DSL_METHODS = [
:after_action,
:around_action,
:before_action,
...
...
]
def process_call(exp)
# ...
when *RAILS_DSL_METHODS + AR_VIRTUAL_DSL_METHODS
_, _, _, (_, new_name), possible_hash = exp
called << new_name
if Sexp === possible_hash && possible_hash.sexp_type == :hash
possible_hash.sexp_body.each_slice(2) do |key, val|
next unless Sexp === val
called << val.last if val.first == :lit
called << val.last.to_sym if val.first == :str
end
end
# ...
end
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As with most things, with the right tools,
the job isn’t very difficult.
Customization is easy.
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Other things that are easy:
Executing this code on your project, right now.
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debride
https://github.com/seattlerb/debride
debride (v): To remove dead, contaminated, or
adherent tissue and/or foreign material.
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ruby_parser
racc
Ruby code (.rb)
Ruby23Parser
Parsing
File.read()
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ruby_parser
racc
sexp_processor
Ruby code (.rb)
Ruby23Parser
MethodBasedSexpProcessor
SexpProcessor
Parsing
Generic processing
File.read()
s-expression (parse tree)
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ruby_parser
racc
sexp_processor
Ruby code (.rb)
Ruby23Parser
MethodBasedSexpProcessor
SexpProcessor
Parsing
Generic processing
File.read()
s-expression (parse tree)
Call processing and reporting
debride Debride
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$ debride [options] files_or_dirs
-e, --exclude FILE1,FILE2,ETC
-w, --whitelist PATTERN
-f, --focus PATH
-r, --rails
-v, --verbose
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- @called = Set.new
+ @called = Hash.new { |h,k| h[k] = 0 }
- called << method_name
+ called[method_name] += 1
- not_called = known.keys - called.to_a
+ called_once = called.select { |_, v| v == 1 }
API Quality Control - Single call methods
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Future considerations:
• Actually push the work I’ve done upstream
✴ Bug fixes
✴ Cleanup
✴ Potential features
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But wait, there’s more!
Unused by Josh Clayton
https://github.com/joshuaclayton/unused
Written in Haskell, this project utilizes ctags
to statically find unused code
OldeCodeFinder by Tom Copeland
https://github.com/tcopeland/olde_code_finder
A Ruby gem checking code content by date and authorship
Thanks, Juanito!
Here’s a few…
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No code is faster than no code.
No code has fewer bugs than no code.
No code is easier to understand than no code.
No code is more maintainable than no code.
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Thank you!
Questions?
chrisarcand
chrisarcand
www.chrisarcand.com