assert: minor error message improvements

Adjust indentations and fix a typo.

PR-URL: #20315
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>

lib/internal/errors.js

@@ -360,13 +360,10 @@ function createErrDiff(actual, expected, operator) {
 
   // Strict equal with identical objects that are not identical by reference.
   if (identical === maxLines) {
-    let base = 'Input object identical but not reference equal:';
-
-    if (operator !== 'strictEqual') {
-      // This code path should not be possible to reach.
-      // The output is identical but it is not clear why.
-      base = 'Input objects not identical:';
-    }
+    // E.g., assert.deepStrictEqual(Symbol(), Symbol())
+    const base = operator === 'strictEqual' ?
+      'Input objects identical but not reference equal:' :
+      'Input objects not identical:';
 
     // We have to get the result again. The lines were all removed before.
     const actualLines = inspectValue(actual);
@@ -380,7 +377,7 @@ function createErrDiff(actual, expected, operator) {
       }
     }
 
-    return `${base}\n\n  ${actualLines.join('\n  ')}\n`;
+    return `${base}\n\n${actualLines.join('\n')}\n`;
   }
   return `${msg}${skipped ? skippedMsg : ''}\n${res}${other}${end}`;
 }
@@ -448,7 +445,7 @@ class AssertionError extends Error {
         if (res.length === 1) {
           super(`${base} ${res[0]}`);
         } else {
-          super(`${base}\n\n  ${res.join('\n  ')}\n`);
+          super(`${base}\n\n${res.join('\n')}\n`);
         }
       } else {
         let res = util.inspect(actual);

test/parallel/test-assert.js

@@ -599,14 +599,13 @@ assert.throws(
   });
 
   // notDeepEqual tests
-  message = 'Identical input passed to notDeepStrictEqual:\n\n' +
-            '  [\n    1\n  ]\n';
+  message = 'Identical input passed to notDeepStrictEqual:\n\n[\n  1\n]\n';
   assert.throws(
     () => assert.notDeepEqual([1], [1]),
     { message });
 
   message = 'Identical input passed to notDeepStrictEqual:' +
-        `\n\n  [${'\n    1,'.repeat(25)}\n  ...\n`;
+        `\n\n[${'\n  1,'.repeat(25)}\n...\n`;
   const data = Array(31).fill(1);
   assert.throws(
     () => assert.notDeepEqual(data, data),
@@ -901,7 +900,7 @@ assert.throws(() => { throw null; }, 'foo');
 assert.throws(
   () => assert.strictEqual([], []),
   {
-    message: 'Input object identical but not reference equal:\n\n  []\n'
+    message: 'Input objects identical but not reference equal:\n\n[]\n'
   }
 );