fix(std/node): fix readFile types, add encoding types (#6451)

1 files changed, 29 insertions, 7 deletions

diff --git a/std/node/_fs/_fs_common.ts b/std/node/_fs/_fs_common.ts
index bf7c0f675..43d3b8064 100644
--- a/std/node/_fs/_fs_common.ts
+++ b/std/node/_fs/_fs_common.ts
@@ -4,11 +4,32 @@ import { notImplemented } from "../_utils.ts";
 
 export type CallbackWithError = (err?: Error | null) => void;
 
+export type TextEncodings =
+  | "ascii"
+  | "utf8"
+  | "utf-8"
+  | "utf16le"
+  | "ucs2"
+  | "ucs-2"
+  | "base64"
+  | "latin1"
+  | "hex";
+export type BinaryEncodings = "binary";
+export type Encodings = TextEncodings | BinaryEncodings;
+
 export interface FileOptions {
-  encoding?: string;
+  encoding?: Encodings;
   flag?: string;
 }
 
+export type TextOptionsArgument =
+  | TextEncodings
+  | ({ encoding: TextEncodings } & FileOptions);
+export type BinaryOptionsArgument =
+  | BinaryEncodings
+  | ({ encoding: BinaryEncodings } & FileOptions);
+export type FileOptionsArgument = Encodings | FileOptions;
+
 export interface WriteFileOptions extends FileOptions {
   mode?: number;
 }
@@ -26,8 +47,8 @@ export function isFileOptions(
 }
 
 export function getEncoding(
-  optOrCallback?: FileOptions | WriteFileOptions | Function | string
-): string | null {
+  optOrCallback?: FileOptions | WriteFileOptions | Function | Encodings | null
+): Encodings | null {
   if (!optOrCallback || typeof optOrCallback === "function") {
     return null;
   }
@@ -38,13 +59,15 @@ export function getEncoding(
   return encoding;
 }
 
-export function checkEncoding(encoding: string | null): string | null {
+export function checkEncoding(encoding: Encodings | null): Encodings | null {
   if (!encoding) return null;
   if (encoding === "utf8" || encoding === "utf-8") {
     return "utf8";
   }
-  if (encoding === "buffer") {
-    return "buffer";
+  if (encoding === "binary") {
+    return "binary";
+    // before this was buffer, however buffer is not used in Node
+    // node -e "require('fs').readFile('../world.txt', 'buffer', console.log)"
   }
 
   const notImplementedEncodings = [
@@ -53,7 +76,6 @@ export function checkEncoding(encoding: string | null): string | null {
     "base64",
     "hex",
     "ascii",
-    "binary",
     "ucs2",
   ];