assert: validate the block return type

This makes sure the returned value when calling `block` is actually
of type promise in case `assert.rejects` or `assert.doesNotReject`
is called.

PR-URL: https://github.com/nodejs/node/pull/19886
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>

2 files changed, 17 insertions, 1 deletions

diff --git a/lib/assert.js b/lib/assert.js
index 62847e55c3..05b43b5b54 100644
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -30,7 +30,8 @@ const {
   errorCache,
   codes: {
     ERR_AMBIGUOUS_ARGUMENT,
-    ERR_INVALID_ARG_TYPE
+    ERR_INVALID_ARG_TYPE,
+    ERR_INVALID_RETURN_VALUE
   }
 } = require('internal/errors');
 const { openSync, closeSync, readSync } = require('fs');
@@ -455,6 +456,11 @@ async function waitForActual(block) {
   if (typeof block === 'function') {
     // Return a rejected promise if `block` throws synchronously.
     resultPromise = block();
+    // Fail in case no promise is returned.
+    if (!checkIsPromise(resultPromise)) {
+      throw new ERR_INVALID_RETURN_VALUE('instance of Promise',
+                                         'block', resultPromise);
+    }
   } else if (checkIsPromise(block)) {
     resultPromise = block;
   } else {
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
index 4823f0b65c..88c7f86eb9 100644
--- a/lib/internal/errors.js
+++ b/lib/internal/errors.js
@@ -904,6 +904,16 @@ E('ERR_INVALID_PROTOCOL',
   TypeError);
 E('ERR_INVALID_REPL_EVAL_CONFIG',
   'Cannot specify both "breakEvalOnSigint" and "eval" for REPL', TypeError);
+E('ERR_INVALID_RETURN_VALUE', (input, name, value) => {
+  let type;
+  if (value && value.constructor && value.constructor.name) {
+    type = `instance of ${value.constructor.name}`;
+  } else {
+    type = `type ${typeof value}`;
+  }
+  return `Expected ${input} to be returned from the "${name}"` +
+          ` function but got ${type}.`;
+}, TypeError);
 E('ERR_INVALID_SYNC_FORK_INPUT',
   'Asynchronous forks do not support Buffer, Uint8Array or string input: %s',
   TypeError);