noctcore-code-quality/no-elided-code-comments

Ban // ... existing code ... placeholders that stand in for deleted code.

Recommended preset: error · Autofix: no · Suggestions: no · Type information: not needed

Why

When an agent rewrites a file from an abbreviated draft, it writes placeholders like // ... existing code ... or // rest of the function unchanged where it skipped code. If the edit is applied as a whole-file write instead of a patch, the placeholder lands in the file and the code it stood for is gone. The file still parses and often still type-checks, so nothing else notices: a method disappears, a case goes missing, and the only trace is a comment claiming nothing changed. VS Code’s agent mode shipped with this failure (microsoft/vscode#254789).

The comment is a strong signal on its own. Nobody writes “rest of the code unchanged” on purpose in a file they are keeping.

What it flags

Line and block comments (JSDoc /** … */ blocks are exempt, @example code included) whose whole text is an elision placeholder, matched case-insensitively and with ... or … allowed around it:

• A reference to left-out code: rest of the code, rest of the function unchanged, ... existing code ..., ... other methods ..., other handlers omitted for brevity, keep existing imports .... The generic forms (“other methods”, “more tests”) only count with an ellipsis or a word such as unchanged, omitted, here or as before, because on their own they read as section headers. Data nouns (fields, props, state, config, …) need more: omitted / here / for brevity, or ellipses on both sides (// ... other props ...), since a test that writes // other fields unchanged above its assertions is describing data, not skipping code.
• A fill-in placeholder: your code here, add your own logic here, implementation goes here.
• A claim that the rest did not change: everything else stays the same, (unchanged), ... same as before.

Incorrect · 3 reports

class Cart {
  add(item: Item) {
    this.items.push(item);
  }

  // ... other methods ...
}

function total(cart: Cart) {
  /* rest of the function unchanged */
}

function checkout() {
  // your code here
}

Correct

class Cart {
  add(item: Item) {
    this.items.push(item);
  }

  remove(id: string) {
    this.items = this.items.filter((item) => item.id !== id);
  }
}

// Other helpers
function total(cart: Cart) {
  return cart.items.reduce((sum, item) => sum + item.price, 0);
}

How to fix

Restore the missing code from version control (git diff shows what the edit removed), then delete the comment. If the code really was meant to go, delete the comment alone.

What it does not flag

It is deliberately narrow: the comment has to be the placeholder and nothing else. An ellipsis in prose (// wait... this is intentional), commented-out spread syntax (// return { ...rest }), a bare /* ... */, a sentence that happens to say “the rest of the function assumes…”, and a plain // unchanged note next to a value are all left alone. So are comments that start with TODO, FIXME, XXX or HACK: a tracked placeholder is a known gap, not a silent deletion.

Correct

function sum(values: number[]) {
  // wait... this is intentional: an empty list sums to zero.
  // The rest of the function assumes the list is sorted.
  return values.reduce((total, value) => total + value, 0);
}

const next = {
  ...previous,
  // unchanged
  retries: 3,
};

// TODO: implementation goes here

When not to use it

In documentation or code-generation templates where a // your code here placeholder is the intended output. Disable it for those files.