1217315 - Remove use of for-each from docshell/.

Status: RESOLVED FIXED

(Firefox :: General, defect)

Description

[Tooru Fujisawa [:arai]]

Need to replace non-standard for-each with one of:
  * for-of
  * for-in
  * array.map/array.filter for array-comprehension
as a part of bug 1083470.

converting rules are following:
  * for-each
    * for each (let x in array) { ... }
      -> for (let x of array) { ... }
    * for each (let x in object) { ... }
      -> for (let key in object) { let x = object[key]; ... }
    * for each (let [key, value] in Iterator(object)) { ... }
      -> for (let key in object) { let value = object[key]; ... }
    * for each (let x in array) { ... }
      where array can be null or undefined
      -> if (array) { for (let x of array) { ... } }

  * legacy array comprehension with for-each
    (newer array comprehension is now also a non-standard feature, I'd like to go with map/filter)
    * [EXPR for each (x in array)]
      -> array.map(x => EXPR)
    * [EXPR for each (x in array) if (COND)]
      -> array.filter(x => COND).map(x => EXPR)
    * [x for each (x in array) if (COND)]
      -> array.filter(x => COND)
    * [EXPR for each ([i, x] in Iterator(array)) if (g(x, i)]
      -> array.filter((x, i) => g(x, i)).map((x => EXPR)
    * [EXPR for each (x in arraylike)]
      -> Array.from(arraylike).map(x => EXPR)
    * [EXPR for each (x in string)]
      -> Array.prototype.slice.call(string).map(x => EXPR)
         // Array.from behaves differently for surrogate-pair

Comment 1

[Tooru Fujisawa [:arai]]

Attachment: Remove for-each from docshell/.

Almost green on try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=77c5563839da

Comment 2

[Tooru Fujisawa [:arai]]

Attachment: Types for some complicated cases.

here's the result of investigation for some complicated case.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Comment on attachment 8677295 [details] [diff] [review]
Remove for-each from docshell/.

Crazy inconsistency in the language if
'in' can deal with null/undefined but 'of' can't, IMHO.

Comment 4

[Tooru Fujisawa [:arai]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/05bb7ca32591b299a15588ac01440ad9a91f67f8
Bug 1217315 - Remove for-each from docshell/. r=smaug

Comment 5

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/05bb7ca32591