Merge pull request #92 from vim-denops/imp-load

👍 Do NOT reload Vim script files on `load()`

Author: lambdalisue

denops_std/helper/README.md

@@ -167,3 +167,56 @@ export async function main(denops: Denops): Promise<void> {
   await load(denops, new URL("https://example.com/foo.vim"));
 }
 ```
+
+It does nothing if the `url` is already loaded unless `force` option is
+specified like:
+
+```typescript
+import { Denops } from "https://deno.land/x/denops_std/mod.ts";
+import { load } from "https://deno.land/x/denops_std/helper/mod.ts";
+
+export async function main(denops: Denops): Promise<void> {
+  const url = new URL("../../foo.vim", import.meta.url);
+
+  // Line below loads a script
+  await load(denops, url);
+
+  // Line below does nothing while `url` is already loaded.
+  await load(denops, url);
+
+  // Line below loads the script while `force` option is specified.
+  await load(denops, url, { force: true });
+}
+```
+
+It returns `true` when the script is loaded. Otherwise, it returns `false` like:
+
+```typescript
+import { Denops } from "https://deno.land/x/denops_std/mod.ts";
+import { load } from "https://deno.land/x/denops_std/helper/mod.ts";
+
+export async function main(denops: Denops): Promise<void> {
+  const url = new URL("../../foo.vim", import.meta.url);
+
+  console.log(await load(denops, url));
+  // -> true
+
+  console.log(await load(denops, url));
+  // -> false
+
+  console.log(await load(denops, url, { force: true }));
+  // -> true
+}
+```
+
+Note that denops plugins works on individual threads so developers should add a
+source guard on a Vim script as well like:
+
+```vim
+if has('g:loaded_xxxxx')
+  finish
+endif
+let g:loaded_xxxxx = 1
+
+" Define functions or whatever
+```

denops_std/helper/load.ts

@@ -1,19 +1,34 @@
 import { Denops, fs, hash, path } from "../deps.ts";
 import { execute } from "./execute.ts";
 
+const loaded = new Set<URL>();
+
+export type LoadOptions = {
+  force?: boolean;
+};
+
 /**
- * Load Vim script in local/remote URL
+ * Load a Vim script in a local/remote URL
+ *
+ * It does nothing if the `url` is already loaded unless `force` option is specified.
+ * It returns `true` when the script is loaded. Otherwise, it returns `false`.
  */
 export async function load(
   denops: Denops,
   url: URL,
-): Promise<void> {
+  options: LoadOptions = {},
+): Promise<boolean> {
+  if (!options.force && loaded.has(url)) {
+    return false;
+  }
   const scriptPath = await ensureLocalFile(url);
   await execute(
     denops,
     "execute printf('source %s', fnameescape(scriptPath)) ",
     { scriptPath },
   );
+  loaded.add(url);
+  return true;
 }
 
 async function ensureLocalFile(url: URL): Promise<string> {