[JS] Add support for System.Array.Resize

src/Fable.Cli/CHANGELOG.md

@@ -103,6 +103,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
         * `DateTime.TryParse`
         * `DateTime.SpecifyKind`
 
+#### JavaScript
+
+* [GH-3715](https://github.com/fable-compiler/Fable/pull/3715) Add support for System.Array.Resize (by @chkn)
+
 ## 4.9.0 - 2023-12-14
 
 ### Fixed

src/Fable.Transforms/Replacements.fs

@@ -3369,6 +3369,22 @@ let arrays
         )
         |> Some
     | "GetEnumerator", Some arg, _ -> getEnumerator com r t arg |> Some
+    | "Resize", None, args ->
+        let args =
+            args @ [ getZero com ctx (List.head i.GenericArgs) ]
+            |> injectArg com ctx r "Array" "resize" i.GenericArgs
+
+        Helper.LibCall(
+            com,
+            "Array",
+            "resize",
+            Unit,
+            args,
+            i.SignatureArgTypes,
+            genArgs = i.GenericArgs,
+            ?loc = r
+        )
+        |> Some
     | _ -> None
 
 let arrayModule

src/Fable.Transforms/ReplacementsInject.fs

@@ -50,6 +50,7 @@ let fableReplacementsModules =
                     "insertAt", (Types.arrayCons, 0)
                     "insertManyAt", (Types.arrayCons, 0)
                     "updateAt", (Types.arrayCons, 0)
+                    "resize", (Types.arrayCons, 0)
                 ]
             "List",
             Map

src/fable-library/Array.fs

@@ -1405,3 +1405,29 @@ let updateAt
                 xs.[i]
 
     target
+
+let resize
+    (xs: byref<'T[]>)
+    (newSize: int)
+    ([<OptionalArgument>] zero: 'T option)
+    ([<OptionalArgument; Inject>] cons: Cons<'T>)
+    : unit
+    =
+    if newSize < 0 then
+        invalidArg "newSize" "The input must be non-negative."
+
+    let len = xs.Length
+
+    if newSize < len then
+        xs <- subArrayImpl xs 0 newSize
+
+    elif newSize > len then
+        let target = allocateArrayFromCons cons newSize
+        copyTo xs 0 target 0 len
+
+        xs <-
+            fillImpl
+                target
+                (defaultArg zero Unchecked.defaultof<_>)
+                len
+                (newSize - len)

tests/Js/Main/ArrayTests.fs

@@ -1190,4 +1190,13 @@ let tests =
         equal c1 true
         equal c2 -1
         equal c3 1
+
+    testCase "Array.Resize works" <| fun () ->
+        let mutable xs = [|1; 2; 3; 4; 5|]
+        Array.Resize(&xs, 3)
+        xs |> equal [|1; 2; 3|]
+        Array.Resize(&xs, 7)
+        xs |> equal [|1; 2; 3; 0; 0; 0; 0|]
+        Array.Resize(&xs, 0)
+        xs |> equal [||]
   ]