👍 Add echoerr to helper module

Author: lambdalisue

denops_std/helper/README.md

@@ -6,7 +6,7 @@
 
 ## Usage
 
-### echo
+### echo / echoerr
 
 Use `echo()` to show messages on the cmdline area. It is required while Vim
 won't show messages reported from channel commands and it won't pause multi-line
@@ -18,10 +18,11 @@ properly show multi-line messages with `echomsg` from asynchronous context.
 
 ```typescript
 import { Denops } from "https://deno.land/x/denops_std/mod.ts";
-import { echo } from "https://deno.land/x/denops_std/helper/mod.ts";
+import { echo, echoerr } from "https://deno.land/x/denops_std/helper/mod.ts";
 
 export async function main(denops: Denops): Promise<void> {
   await echo(denops, "Hello\nWorld!");
+  await echoerr(denops, "This is error message");
 }
 ```
 

denops_std/helper/echo.ts

@@ -1,5 +1,6 @@
 import { deferred, Denops } from "../deps.ts";
 import * as anonymous from "../anonymous/mod.ts";
+import { batch } from "../batch/mod.ts";
 import { load } from "./load.ts";
 
 /**
@@ -23,6 +24,20 @@ export function echo(denops: Denops, message: string): Promise<void> {
   }
 }
 
+/**
+ * Echo message as an error message.
+ *
+ * Note that this function just use ErrorMsg highlight and is not equivalent
+ * to `echoerr` command in Vim/Neovim.
+ */
+export async function echoerr(denops: Denops, message: string): Promise<void> {
+  await batch(denops, async (denops) => {
+    await denops.cmd("echohl ErrorMsg");
+    await echo(denops, message);
+    await denops.cmd("echohl None");
+  });
+}
+
 async function echoVim(denops: Denops, message: string): Promise<void> {
   await load(denops, new URL("./echo.vim", import.meta.url));
   const waiter = deferred<void>();