perf: avoid ToCharArray allocations in HtmlParser

- Pop(count): use Array.init instead of [| 0..n-1 |] |> Array.map
- EmitToAttributeValue: iterate string directly instead of ToCharArray()
- Cons(char array): use StringBuilder.Append(char[]) instead of Array.iter
- Cons(string): use StringBuilder.Append(string) directly
- CDATA marker: pass string literal to Cons instead of ToCharArray()

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

RELEASE_NOTES.md

@@ -1,5 +1,9 @@
 # Release Notes
 
+## 8.1.7 - Apr 7 2026
+
+- Performance: HTML parser avoids `ToCharArray()` allocations in several code paths: `EmitToAttributeValue` now iterates the substituted string directly; `Cons(char[])` and `Cons(string)` use `StringBuilder.Append` directly; `Pop(count)` uses `Array.init` instead of creating an integer range array; CDATA opening marker no longer creates a temporary `char[]`.
+
 ## 8.1.6 - Apr 5 2026
 
 - Performance: `NameUtils.nicePascalName` now writes directly to a `StringBuilder` instead of using lazy sequences and intermediate string allocations per segment; also removes a redundant per-segment `ToCharArray()` call. `NameUtils.trimHtml` no longer allocates an intermediate `char[]` for string iteration.

src/FSharp.Data.Html.Core/HtmlParser.fs

@@ -128,7 +128,7 @@ module internal HtmlParser =
         member x.Peek() = x.Reader.PeekChar()
 
         member x.Pop(count) =
-            [| 0 .. (count - 1) |] |> Array.map (fun _ -> x.Reader.ReadChar())
+            Array.init count (fun _ -> x.Reader.ReadChar())
 
         member x.Contents = x.Content.ToString()
         member x.ContentLength = x.Content.Length
@@ -221,7 +221,7 @@ module internal HtmlParser =
             assert (x.InsertionMode = InsertionMode.CharRefMode)
             let content = x.Content.ToString() |> HtmlCharRefs.substitute
 
-            for c in content.ToCharArray() do
+            for c in content do
                 x.ConsAttrValue c
 
             x.Content <- { Contents = StringBuilder() }
@@ -257,8 +257,12 @@ module internal HtmlParser =
 
         member x.Cons() = x.Content.Cons(x.Reader.ReadChar())
         member x.Cons(char: char) = x.Content.Cons(char)
-        member x.Cons(chars: char array) = Array.iter (x.Content.Cons) chars
-        member x.Cons(chars: string) = x.Cons(chars.ToCharArray())
+
+        member x.Cons(chars: char array) =
+            x.Content.Contents.Append(chars) |> ignore
+
+        member x.Cons(chars: string) =
+            x.Content.Contents.Append(chars) |> ignore
 
         member x.ConsTag() =
             match x.Reader.ReadChar() with
@@ -666,7 +670,7 @@ module internal HtmlParser =
                 match new String(Array.append current (state.Pop(5))) with
                 | "DOCTYPE" -> docType state
                 | "[CDATA[" ->
-                    state.Cons("<![CDATA[".ToCharArray())
+                    state.Cons("<![CDATA[")
                     cData 0 state
                 | _ -> bogusComment state