assert: reduce diff noise

Assertion errors that produce a diff show a diff for identical entries
in case one side of the comparison has more object properties than the
other one. Those lines are now taken into account and will not show up
as diverging lines anymore.

Refs: nodejs#22763

Author: BridgeAR

lib/internal/assert.js

@@ -191,29 +191,42 @@ function createErrDiff(actual, expected, operator) {
       res += `\n${green}+${white} ${actualLines[i]}`;
       printedLines++;
     // Lines diverge
-    } else if (actualLines[i] !== expectedLines[i]) {
-      if (cur > 1 && i > 2) {
-        if (cur > 4) {
-          res += `\n${blue}...${white}`;
-          skipped = true;
-        } else if (cur > 3) {
-          res += `\n  ${actualLines[i - 2]}`;
+    } else {
+      const expectedLine = expectedLines[i];
+      let actualLine = actualLines[i];
+      let divergingLines = actualLine !== expectedLine &&
+                           (!actualLine.endsWith(',') ||
+                            actualLine.slice(0, -1) !== expectedLine);
+      if (divergingLines &&
+          expectedLine.endsWith(',') &&
+          expectedLine.slice(0, -1) === actualLine) {
+        divergingLines = false;
+        actualLine += ',';
+      }
+      if (divergingLines) {
+        if (cur > 1 && i > 2) {
+          if (cur > 4) {
+            res += `\n${blue}...${white}`;
+            skipped = true;
+          } else if (cur > 3) {
+            res += `\n  ${actualLines[i - 2]}`;
+            printedLines++;
+          }
+          res += `\n  ${actualLines[i - 1]}`;
+          printedLines++;
+        }
+        lastPos = i;
+        res += `\n${green}+${white} ${actualLine}`;
+        other += `\n${red}-${white} ${expectedLine}`;
+        printedLines += 2;
+      // Lines are identical
+      } else {
+        res += other;
+        other = '';
+        if (cur === 1 || i === 0) {
+          res += `\n  ${actualLine}`;
           printedLines++;
         }
-        res += `\n  ${actualLines[i - 1]}`;
-        printedLines++;
-      }
-      lastPos = i;
-      res += `\n${green}+${white} ${actualLines[i]}`;
-      other += `\n${red}-${white} ${expectedLines[i]}`;
-      printedLines += 2;
-    // Lines are identical
-    } else {
-      res += other;
-      other = '';
-      if (cur === 1 || i === 0) {
-        res += `\n  ${actualLines[i]}`;
-        printedLines++;
       }
     }
     // Inspected object to big (Show ~20 rows max)

test/parallel/test-assert-deep.js

@@ -65,9 +65,13 @@ assert.deepEqual(arr, buf);
     () => assert.deepStrictEqual(buf2, buf),
     {
       code: 'ERR_ASSERTION',
-      message: `${defaultMsgStartFull}\n\n` +
-               '  Buffer [Uint8Array] [\n    120,\n    121,\n    122,\n' +
-               '+   10,\n+   prop: 1\n-   10\n  ]'
+      message: `${defaultMsgStartFull} ... Lines skipped\n\n` +
+               '  Buffer [Uint8Array] [\n' +
+               '    120,\n' +
+               '...\n' +
+               '    10,\n' +
+               '+   prop: 1\n' +
+               '  ]'
     }
   );
   assert.deepEqual(buf2, buf);
@@ -80,9 +84,13 @@ assert.deepEqual(arr, buf);
     () => assert.deepStrictEqual(arr, arr2),
     {
       code: 'ERR_ASSERTION',
-      message: `${defaultMsgStartFull}\n\n` +
-               '  Uint8Array [\n    120,\n    121,\n    122,\n' +
-               '+   10\n-   10,\n-   prop: 5\n  ]'
+      message: `${defaultMsgStartFull} ... Lines skipped\n\n` +
+               '  Uint8Array [\n' +
+               '    120,\n' +
+               '...\n' +
+               '    10,\n' +
+               '-   prop: 5\n' +
+               '  ]'
     }
   );
   assert.deepEqual(arr, arr2);
@@ -822,7 +830,7 @@ assert.throws(
     code: 'ERR_ASSERTION',
     name: 'AssertionError [ERR_ASSERTION]',
     message: `${defaultMsgStartFull}\n\n  ` +
-             '{\n+   a: 4\n-   a: 4,\n-   b: true\n  }'
+             '{\n    a: 4,\n-   b: true\n  }'
   });
 assert.throws(
   () => assert.deepStrictEqual(['a'], { 0: 'a' }),
@@ -891,7 +899,7 @@ assert.deepStrictEqual(obj1, obj2);
   assert.throws(
     () => assert.deepStrictEqual(arrProxy, [1, 2, 3]),
     { message: `${defaultMsgStartFull}\n\n` +
-               '  [\n    1,\n+   2\n-   2,\n-   3\n  ]' }
+               '  [\n    1,\n    2,\n-   3\n  ]' }
   );
   util.inspect.defaultOptions = tmp;