assert: make actual and expected getters

The `actual` and `expected` properties on an instance of
`AssertionError` is now a getter to prevent inspecting these when
inspecting the error. These values will be visible in the error
message and showing them otherwise would decrease the readability
of the error.

PR-URL: #25250
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/assert.js

@@ -395,6 +395,14 @@ class AssertionError extends Error {
  this.operator = operator;
  Error.captureStackTrace(this, stackStartFn);
  }
+
+ [inspect.custom](recurseTimes, ctx) {
+ // This limits the `actual` and `expected` property default inspection to
+ // the minimum depth. Otherwise those values would be too verbose compared
+ // to the actual error message which contains a combined view of these two
+ // input values.
+ return inspect(this, { ...ctx, customInspect: false, depth: 0 });
+ }
 }
 
 module.exports = {

test/parallel/test-assert.js

@@ -1139,3 +1139,14 @@ assert.throws(
  '{\n a: true\n}\n'
  }
 );
+
+{
+ let threw = false;
+ try {
+ assert.deepStrictEqual(Array(100).fill(1), 'foobar');
+ } catch (err) {
+ threw = true;
+ assert(/actual: \[Array],\n expected: 'foobar',/.test(inspect(err)));
+ }
+ assert(threw);
+}