fs: support pseudofiles in promises.readFile

PR-URL: https://github.com/nodejs/node/pull/21497
Fixes: https://github.com/nodejs/node/issues/21331
Refs: http://pubs.opengroup.org/onlinepubs/9699919799/functions/read.html
Refs: https://groups.google.com/forum/#!topic/nodejs-dev/rxZ_RoH1Gn0
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

1 files changed, 31 insertions, 13 deletions

diff --git a/test/parallel/test-fs-promises-readfile.js b/test/parallel/test-fs-promises-readfile.js
index 4334673c30..b1186ad217 100644
--- a/test/parallel/test-fs-promises-readfile.js
+++ b/test/parallel/test-fs-promises-readfile.js
@@ -12,17 +12,35 @@ const fn = path.join(tmpdir.path, 'large-file');
 
 common.crashOnUnhandledRejection();
 
-// Creating large buffer with random content
-const buffer = Buffer.from(
-  Array.apply(null, { length: 16834 * 2 })
-    .map(Math.random)
-    .map((number) => (number * (1 << 8)))
-);
-
-// Writing buffer to a file then try to read it
-writeFile(fn, buffer)
-  .then(() => readFile(fn))
-  .then((readBuffer) => {
-    assert.strictEqual(readBuffer.equals(buffer), true);
-  })
+async function validateReadFile() {
+  // Creating large buffer with random content
+  const buffer = Buffer.from(
+    Array.apply(null, { length: 16834 * 2 })
+      .map(Math.random)
+      .map((number) => (number * (1 << 8)))
+  );
+
+  // Writing buffer to a file then try to read it
+  await writeFile(fn, buffer);
+  const readBuffer = await readFile(fn);
+  assert.strictEqual(readBuffer.equals(buffer), true);
+}
+
+async function validateReadFileProc() {
+  // Test to make sure reading a file under the /proc directory works. Adapted
+  // from test-fs-read-file-sync-hostname.js.
+  // Refs:
+  // - https://groups.google.com/forum/#!topic/nodejs-dev/rxZ_RoH1Gn0
+  // - https://github.com/nodejs/node/issues/21331
+
+  // Test is Linux-specific.
+  if (!common.isLinux)
+    return;
+
+  const hostname = await readFile('/proc/sys/kernel/hostname');
+  assert.ok(hostname.length > 0);
+}
+
+validateReadFile()
+  .then(() => validateReadFileProc())
   .then(common.mustCall());