feat(bun): tryWriteTextFile and tryRenamePath, total write and rename

lib/codegen_deno.ml

@@ -1331,6 +1331,13 @@ let () =
      is the check to make before them (added for kyX). *)
   b "pathExists"
     (fun a -> Printf.sprintf "__as_fs().existsSync(%s)" (arg 0 a));
+  (* Total write and rename: true on success, false on any host error
+     (permission, missing directory, disk full), never a throw. They let a
+     program stage outputs and publish them all or none (added for kyX). *)
+  b "tryWriteTextFile"
+    (fun a -> Printf.sprintf "((p, c) => { try { __as_fs().writeFileSync(p, c, \"utf8\"); return true; } catch (_e) { return false; } })(%s, %s)" (arg 0 a) (arg 1 a));
+  b "tryRenamePath"
+    (fun a -> Printf.sprintf "((f, t) => { try { __as_fs().renameSync(f, t); return true; } catch (_e) { return false; } })(%s, %s)" (arg 0 a) (arg 1 a));
   b "args" (fun _ -> "(globalThis.process?.argv?.slice(2) ?? [])");
   b "exit"
     (fun a -> Printf.sprintf "__as_process().exit(%s)" (arg 0 a));

stdlib/Deno.affine

@@ -82,6 +82,14 @@ pub extern fn statIsDirectory(path: String) -> Bool;
 /// Never throws: the total check to make before the stat predicates above.
 pub extern fn pathExists(path: String) -> Bool;
 
+/// Write `content` to `path` as UTF-8. True on success, false on any host
+/// error (permission, missing directory, disk full); never throws.
+pub extern fn tryWriteTextFile(path: String, content: String) -> Bool;
+
+/// Rename `from` to `to` (replacing `to` when it exists). True on success,
+/// false on any host error; never throws.
+pub extern fn tryRenamePath(from: String, to: String) -> Bool;
+
 /// Recursive walk under `root` — every file path beneath it, depth-first.
 /// Mirrors `std/fs/walk` for the common case (no glob filter; callers
 /// filter by extension). Throws on a missing root via `Deno.readDirSync`.

tests/codegen-bun/host_profile.affine

@@ -14,6 +14,8 @@ extern fn statSize(path: String) -> Int;
 extern fn statIsFile(path: String) -> Bool;
 extern fn statIsDirectory(path: String) -> Bool;
 extern fn pathExists(path: String) -> Bool;
+extern fn tryWriteTextFile(path: String, content: String) -> Bool;
+extern fn tryRenamePath(from: String, to: String) -> Bool;
 extern fn bytesLength(value: Bytes) -> Int;
 extern fn bytesByteAt(value: Bytes, offset: Int) -> Int;
 extern fn args() -> [String];
@@ -29,6 +31,8 @@ pub fn file_size(path: String) -> Int { statSize(path) }
 pub fn is_file(path: String) -> Bool { statIsFile(path) }
 pub fn is_directory(path: String) -> Bool { statIsDirectory(path) }
 pub fn exists(path: String) -> Bool { pathExists(path) }
+pub fn try_write(path: String, content: String) -> Bool { tryWriteTextFile(path, content) }
+pub fn try_rename(from: String, to: String) -> Bool { tryRenamePath(from, to) }
 pub fn argument_count() -> Int { len(args()) }
 
 pub fn environment_value(name: String) -> String {

tests/codegen-bun/host_profile.harness.mjs

@@ -49,6 +49,16 @@ try {
   // pathExists is the total check: false for the removed file, never a throw.
   if (subject.exists(file) !== false) throw new Error("pathExists on a missing path is not false");
   if (subject.exists(nested) !== true) throw new Error("pathExists on a directory is not true");
+  // tryWriteTextFile / tryRenamePath are total: false on a host error, never a throw.
+  const staged = join(nested, "staged.tmp");
+  const published = join(nested, "published.txt");
+  if (subject.try_write(staged, "v1") !== true) throw new Error("tryWriteTextFile failed on a writable path");
+  if (subject.try_write(join(root, "no-such-dir", "x"), "v") !== false) throw new Error("tryWriteTextFile into a missing directory is not false");
+  if (subject.try_write(published, "old") !== true) throw new Error("tryWriteTextFile could not create the target");
+  if (subject.try_rename(staged, published) !== true) throw new Error("tryRenamePath failed");
+  if (subject.read_text(published) !== "v1") throw new Error("tryRenamePath did not replace the target");
+  if (subject.exists(staged) !== false) throw new Error("tryRenamePath left the source behind");
+  if (subject.try_rename(staged, published) !== false) throw new Error("tryRenamePath of a missing source is not false");
 } finally {
   rmSync(root, { recursive: true, force: true });
 }