assert: limit string inspection when logging assertion errors

This makes sure long strings as `actual` or `expected` values on an
`AssertionError` won't be logged completely. This is important as
the actual value is somewhat redundant in combination with the error
message which already logs the difference between the input values.

PR-URL: #28058
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/internal/assert/assertion_error.js

@@ -429,11 +429,37 @@ class AssertionError extends Error {
   }
 
   [inspect.custom](recurseTimes, ctx) {
+    // Long strings should not be fully inspected.
+    const tmpActual = this.actual;
+    const tmpExpected = this.expected;
+
+    for (const name of ['actual', 'expected']) {
+      if (typeof this[name] === 'string') {
+        const lines = this[name].split('\n');
+        if (lines.length > 10) {
+          lines.length = 10;
+          this[name] = `${lines.join('\n')}\n...`;
+        } else if (this[name].length > 512) {
+          this[name] = `${this[name].slice(512)}...`;
+        }
+      }
+    }
+
     // 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 });
+    const result = inspect(this, {
+      ...ctx,
+      customInspect: false,
+      depth: 0
+    });
+
+    // Reset the properties after inspection.
+    this.actual = tmpActual;
+    this.expected = tmpExpected;
+
+    return result;
   }
 }