From 02bce8b7d8d34709abc1dacd96de01c9be95a2ce Mon Sep 17 00:00:00 2001
From: Jack Firth <jackhfirth@gmail.com>
Date: Fri, 30 Aug 2024 20:11:22 -0700
Subject: [PATCH] Add `map-to-for` refactoring (#254)

This is similar to `for-each-to-for` but for refactoring `map` into `for/list`.
---
 .../for-loop-shortcuts-test.rkt               | 99 +++++++++++++++++++
 .../for-loop-shortcuts.rkt                    | 10 ++
 2 files changed, 109 insertions(+)

diff --git a/default-recommendations/for-loop-shortcuts-test.rkt b/default-recommendations/for-loop-shortcuts-test.rkt
index a677f06..c2eba49 100644
--- a/default-recommendations/for-loop-shortcuts-test.rkt
+++ b/default-recommendations/for-loop-shortcuts-test.rkt
@@ -8,6 +8,105 @@ header:
 - #lang racket/base
 
 
+test: "map with short single-form body not refactorable"
+------------------------------
+(define some-list (list 1 2 3))
+(map (λ (x) (* x 2)) some-list)
+------------------------------
+
+
+test: "map with long single-form body to for/list"
+------------------------------
+(define some-list (list 1 2 3))
+(map
+ (λ (a-very-very-very-long-variable-name-thats-so-very-long)
+   (* a-very-very-very-long-variable-name-thats-so-very-long 2))
+ some-list)
+------------------------------
+------------------------------
+(define some-list (list 1 2 3))
+(for/list ([a-very-very-very-long-variable-name-thats-so-very-long (in-list some-list)])
+  (* a-very-very-very-long-variable-name-thats-so-very-long 2))
+------------------------------
+
+
+test: "map with multiple body forms to for/list"
+------------------------------
+(define some-list (list 1 2 3))
+(map
+ (λ (x)
+   (define y (* x 2))
+   (+ x y))
+ some-list)
+------------------------------
+------------------------------
+(define some-list (list 1 2 3))
+(for/list ([x (in-list some-list)])
+  (define y (* x 2))
+  (+ x y))
+------------------------------
+
+
+test: "map with let expression to for/list with definitions"
+------------------------------
+(define some-list (list 1 2 3))
+(map (λ (x) (let ([y 1]) (+ x y))) some-list)
+------------------------------
+------------------------------
+(define some-list (list 1 2 3))
+(for/list ([x (in-list some-list)])
+  (define y 1)
+  (+ x y))
+------------------------------
+
+
+test: "map range to for/list"
+------------------------------
+(require racket/list)
+(map
+ (λ (x)
+   (define y 1)
+   (+ x y))
+ (range 0 10))
+------------------------------
+------------------------------
+(require racket/list)
+(for/list ([x (in-range 0 10)])
+  (define y 1)
+  (+ x y))
+------------------------------
+
+
+test: "map string->list to for/list in-string"
+------------------------------
+(map
+ (λ (c)
+   (displayln c)
+   (char-upcase c))
+ (string->list "hello"))
+------------------------------
+------------------------------
+(for/list ([c (in-string "hello")])
+  (displayln c)
+  (char-upcase c))
+------------------------------
+
+
+test: "map bytes->list to for/list in-bytes"
+------------------------------
+(map
+ (λ (b)
+   (displayln b)
+   (* b 2))
+ (bytes->list #"hello"))
+------------------------------
+------------------------------
+(for/list ([b (in-bytes #"hello")])
+  (displayln b)
+  (* b 2))
+------------------------------
+
+
 test: "for-each with short single-form body not refactorable"
 ------------------------------
 (define some-list (list 1 2 3))
diff --git a/default-recommendations/for-loop-shortcuts.rkt b/default-recommendations/for-loop-shortcuts.rkt
index 81d123c..e6b1782 100644
--- a/default-recommendations/for-loop-shortcuts.rkt
+++ b/default-recommendations/for-loop-shortcuts.rkt
@@ -142,6 +142,15 @@
     #:with (body ...) #'(only-body)))
 
 
+(define-refactoring-rule map-to-for
+  #:description "This `map` operation can be replaced with a `for/list` loop."
+  #:literals (map)
+  [(map function:worthwhile-loop-body-function loop:for-clause-convertible-list-expression)
+   ((~if loop.flat? for/list for*/list)
+    (loop.leading-clause ... [function.x loop.trailing-expression])
+    function.body ...)])
+
+
 (define-refactoring-rule for-each-to-for
   #:description "This `for-each` operation can be replaced with a `for` loop."
   #:literals (for-each)
@@ -303,6 +312,7 @@
          for-each-to-for
          list->set-to-for/set
          list->vector-to-for/vector
+         map-to-for
          named-let-loop-to-for/first-in-vector
          nested-for-to-for*
          or-in-for/and-to-filter-clause