Rotor: A Tool for Renaming Values in OCamls Module System Reuben N. - - PowerPoint PPT Presentation

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Rotor: A Tool for Renaming Values in OCamls Module System Reuben N. - - PowerPoint PPT Presentation

Sep 03, 2023 120 likes •420 views

Rotor: A Tool for Renaming Values in OCamls Module System Reuben N. S. Rowe, Hugo Fre, Simon J. Thompson, Scott Owens University of Kent, Canterbury Third International Workshop on Refactoring Tuesday 28 th May 2019, Montral, Canada

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SLIDE 1

Rotor: A Tool for Renaming Values in OCaml’s Module System

Reuben N. S. Rowe, Hugo Férée, Simon J. Thompson, Scott Owens University of Kent, Canterbury Third International Workshop on Refactoring Tuesday 28th May 2019, Montréal, Canada

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SLIDE 2

Why OCaml?

  • OCaml is a functional programming language
  • It is industrially relevant
  • Used by over 50 companies
  • 600 publicly released pacakges/libraries
  • > 11,000 open source projects
  • The module system presents interesting challenges
  • No existing tool support for refactoring

1/10

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SLIDE 3

Renaming: A First Step

  • Only substitute identifiers (no new code)
  • Preserve behaviour/correctness (incl. compilability)
  • Keep the footprint minimal (not simply ‘replace all’)
  • This requires a ‘whole program’ analysis

2/10

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SLIDE 4

Renaming in OCaml is Hard!

Expressiveness of the module system introduce complications:

  • Explicit module type annotations (i.e. interfaces)
  • Module and module type include
  • Module and module type aliasing
  • Module type constraints
  • Functors

3/10

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SLIDE 5

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;;

4/10

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SLIDE 6

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;;

4/10

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SLIDE 7

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;;

4/10

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SLIDE 8

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;; reference to parent module

4/10

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SLIDE 9

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;; reference to parent module

4/10

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SLIDE 10

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;; reference to parent module

4/10

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SLIDE 11

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;;

4/10

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SLIDE 12

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;;

4/10

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SLIDE 13

Example: Module Includes and Aliases

module A = struct let foo = 2 let bar = "hello" end module B = struct include A let bar = "world" end module C = (A : sig val foo : int end) ;; print_int (A.foo + B.foo + C.foo) ;; print_string (A.bar ^ " " ^ B.bar) ;; dependencies: A.foo, B.foo, C.foo

4/10

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SLIDE 14

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 15

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 16

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 17

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 18

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 19

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 20

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 21

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;;

5/10

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SLIDE 22

Example: Functors

module type Stringable = sig type t val to_string : t -> string end module Pair(X : Stringable)(Y : Stringable) = struct type t = X.t * Y.t let to_string (x, y) = (X.to_string x) ^ " " ^ (Y.to_string y) end module Int = struct type t = int let to_string i = string_of_int i end module String = struct type t = string let to_string s = s end module P = Pair(Int)(String) ;; print_endline (P.to_string (5, "Gold Rings!")) ;; dependencies: Int.to_string, String.to_string, Stringable.to_string, Pair[1].to_string, Pair[2].to_string

5/10

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SLIDE 23

Rotor: Main Features

  • Implemented in OCaml itself
  • Visitor classes used to manipulate ASTs
  • Performs fine-grained module dependency analysis
  • Outputs detailed information on renaming dependencies

6/10

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SLIDE 24

Experimental Evaluation

  • OCaml compiler

(~500 files, ~2650 test cases)

  • Re-compilation successful for 70% of cases
  • Jane Street standard library overlay

(~900 files, ~3000 test cases)

  • Re-compilation successful for 37% of cases
  • 46% fail due to use of language preprocessor
  • 5% require changes in external libraries

7/10

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SLIDE 25

Experimental Evaluation

OCaml Compiler Codebase Files Hunks Deps

  • Avg. Hunks/File

Max 19 59 35 15.0 Mean 3.8 5.9 1.6 1.5 Mode 3 3 1 1.0 Jane Street Standard Library Overlay Files Hunks Deps

  • Avg. Hunks/File

Max 50 128 1127 5.7 Mean 5.0 7.5 24.0 1.3 Mode 3 3 19 1.0

8/10

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SLIDE 26

Conclusions

  • Big impact for automatic refactoring in functional

programming

  • OCaml’s module system introduces much complexity
  • Require a notion of refactoring dependency
  • Much work still to be done!

9/10

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SLIDE 27

Future Work

  • Handle more language features
  • first-class modules, module type extraction,

type-level module aliases

  • Other renamings
  • modules, module types, types, record fields, constructors,

classes/methods

  • More sophisticated renamings strategies
  • Other refactorings
  • rename/add/remove function parameter,

function generalisation, etc.

  • IDE/build system integration

10/10

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SLIDE 28

Thank You!

https://gitlab.com/trustworthy-refactoring/refactorer