switch from fs-ext to an ffi implementation

fs-ext is problematic since it requires native .node files but doesn’t provide prebuilds, which makes it hard to use it with a github action and with our Electron app.

Author: mxcl

.github/deno-to-node.ts

@@ -13,7 +13,7 @@ dependencies:
   npmjs.com: '*'
 ---*/
 
-import { build, emptyDir } from "https://deno.land/x/dnt@0.35.0/mod.ts";
+import { build, emptyDir } from "https://deno.land/x/dnt@0.36.0/mod.ts";
 import SemVer from "../src/utils/semver.ts";
 
 await emptyDir("./dist");
@@ -61,9 +61,6 @@ await build({
       "is-what": "^4",
       "outdent": "^0.8",
     },
-    devDependencies: {
-      "@types/fs-ext": "^2"
-    },
   },
   postBuild() {
     Deno.copyFileSync("LICENSE.txt", "dist/LICENSE.txt");

src/prefab/install.test.ts

@@ -1,6 +1,6 @@
 import { useTestConfig as useTestConfigBase } from "../hooks/useConfig.test.ts"
-import { assert, assertEquals } from "deno/testing/asserts.ts"
-import install, { ConsoleLogger } from "./install.ts"
+import { assert, assertEquals, assertFalse } from "deno/testing/asserts.ts"
+import install, { ConsoleLogger, Logger } from "./install.ts"
 import { stub } from "deno/testing/mock.ts"
 import SemVer from "../utils/semver.ts"
 import { Package } from "../types.ts"
@@ -41,16 +41,25 @@ Deno.test("install()", async runner => {
   })
 })
 
-Deno.test("install lock tests", async () => {
+Deno.test("install locks", async () => {
   const pkg: Package = {
     project: "tea.xyz/brewkit",
     version: new SemVer("0.30.0")
   }
 
   const conf = useTestConfig()
 
-  const installer1 = install(pkg)
-  const installer2 = install(pkg)
+  let unlocked_once = false
+  const logger: Logger = {
+    downloading: () => assertFalse(unlocked_once),
+    locking: () => {},
+    installed: () => {},
+    installing: () => assertFalse(unlocked_once),
+    unlocking: () => unlocked_once = true
+  }
+
+  const installer1 = install(pkg, logger)
+  const installer2 = install(pkg, logger)
 
   const [install1, install2] = await Promise.all([installer1, installer2])
 

src/prefab/install.ts

@@ -52,8 +52,8 @@ export default async function install(pkg: Package, logger?: Logger): Promise<In
   const shelf = tea_prefix.join(pkg.project)
 
   logger?.locking(pkg)
-  const { rid } = await Deno.open(shelf.mkdir('p').string)
-  await flock(rid, 'ex')
+  const { rid: fd } = await Deno.open(shelf.mkdir('p').string)
+  await flock(fd, 'ex')
 
   try {
     const already_installed = await cellar.has(pkg)
@@ -125,8 +125,8 @@ export default async function install(pkg: Package, logger?: Logger): Promise<In
     throw err
   } finally {
     logger?.unlocking(pkg)
-    await flock(rid, 'un')
-    Deno.close(rid)  // docs aren't clear if we need to do this or not
+    await flock(fd, 'un')
+    Deno.close(fd)  // docs aren't clear if we need to do this or not
   }
 }
 

src/utils/flock.node.ts

@@ -1,15 +1,21 @@
-import { flock as flock_base } from "npm:fs-ext@2.0.0"
-
-function flock(fd: number, op: 'ex' | 'un') {
-  return new Promise<void>((resolve, reject) => {
-    flock_base(fd, op, (err: Error | null) => {
-      if (err) {
-        reject(err)
-      } else {
-        resolve()
-      }
-    })
-  })
+import koffi from 'npm:koffi@2'
+import * as util from "node:util"
+import host from "./host.ts"
+
+const filename = host().platform == 'darwin' ? 'libSystem.dylib' : 'libc.so.6'
+const libc = koffi.load(filename)
+
+const LOCK_EX = 2;
+const LOCK_UN = 8;
+
+const cflock = libc.func('int flock(int, int)');
+const flockAsync = util.promisify(cflock.async);
+
+async function flock(fd: number, op: 'un' | 'ex') {
+  const rv = await flockAsync(fd, op == 'ex' ? LOCK_EX : LOCK_UN);
+  if (rv === -1) {
+    throw new Error("flock failed") // TODO read errno
+  }
 }
 
 export { flock }