Merge pull request #119 from vim-denops/feat-helper

Add `echoerr` and `friendlyCall` 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 +18,35 @@ 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");
+}
+```
+
+### friendlyCall
+
+Use `friendlyCall()` to call given function and print a friendly error message
+(without stack trace) on failure. It's mainly designed for `dispatcher`
+functions.
+
+Note that it prints a stack trace when denops is running in debug mode.
+
+```typescript
+import { Denops } from "https://deno.land/x/denops_std/mod.ts";
+import { friendlyCall } from "https://deno.land/x/denops_std/helper/mod.ts";
+
+export async function main(denops: Denops): Promise<void> {
+  denops.dispatcher = {
+    "say": () => {
+      return friendlyCall(denops, async () => {
+        // Do whatever you want.
+        throw new Error("Some error occured");
+      });
+    },
+  };
 }
 ```
 

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 +24,44 @@ 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");
+  });
+}
+
+/**
+ * Call given function and print a friendly error message (without stack trace) on failure.
+ *
+ * Print a stack trace when denops is running in debug mode.
+ */
+export async function friendlyCall(
+  denops: Denops,
+  fn: () => Promise<unknown>,
+): Promise<unknown> {
+  if (denops.meta.mode === "debug") {
+    return await fn();
+  }
+  try {
+    return await fn();
+  } catch (e: unknown) {
+    if (e instanceof Error) {
+      const err: Error = e;
+      await echoerr(denops, `[${denops.name}]: ${err.message}`);
+    } else {
+      throw e;
+    }
+  }
+}
+
 async function echoVim(denops: Denops, message: string): Promise<void> {
   await load(denops, new URL("./echo.vim", import.meta.url));
   const waiter = deferred<void>();