bvaughn/react-virtualized · critical · Error

Invalid size returned for cell ${i} of value ${size}

Error message

Invalid size returned for cell ${i} of value ${size}

What it means

The cell size getter (`_cellSizeGetter`) returned undefined or NaN for a cell index, which the manager treats as a logic error and throws. null is allowed (it means CellMeasurer hasn't measured that index yet and yields a 0-size placeholder), but undefined/NaN indicate a broken size function. This is a hard error because layout math cannot proceed.

Source

Thrown at source/Grid/utils/CellSizeAndPositionManager.js:112

    if (index < 0 || index >= this._cellCount) {
      throw Error(
        `Requested index ${index} is outside of range 0..${this._cellCount}`,
      );
    }

    if (index > this._lastMeasuredIndex) {
      let lastMeasuredCellSizeAndPosition = this.getSizeAndPositionOfLastMeasuredCell();
      let offset =
        lastMeasuredCellSizeAndPosition.offset +
        lastMeasuredCellSizeAndPosition.size;

      for (var i = this._lastMeasuredIndex + 1; i <= index; i++) {
        let size = this._cellSizeGetter({index: i});

        // undefined or NaN probably means a logic error in the size getter.
        // null means we're using CellMeasurer and haven't yet measured a given index.
        if (size === undefined || isNaN(size)) {
          throw Error(`Invalid size returned for cell ${i} of value ${size}`);
        } else if (size === null) {
          this._cellSizeAndPositionData[i] = {
            offset,
            size: 0,
          };

          this._lastBatchedIndex = index;
        } else {
          this._cellSizeAndPositionData[i] = {
            offset,
            size,
          };

          offset += size;

          this._lastMeasuredIndex = index;
        }
      }

View on GitHub (pinned to c737715486)

Solutions

1. Make the size getter return a number for every index < cellCount; add a fallback default.
2. Coerce with Number() and validate with Number.isFinite before returning.
3. Ensure any data the getter depends on is loaded before rendering, or use CellMeasurer (returning null) instead.
4. Check for missing-return branches in the size function.

Example fix

// before
rowHeight={({index}) => heights[index]}

// after
rowHeight={({index}) => {
  const h = heights[index];
  return typeof h === 'number' && Number.isFinite(h) ? h : 32;
}}

const safeSize = (i) => {
  const s = getSize(i);
  if (s === null) return null; // CellMeasurer pending
  const n = Number(s);
  if (!Number.isFinite(n)) throw new Error(`size getter returned invalid value for cell ${i}: ${s}`);
  return n;
};

const isValidSize = (s) => s === null || (typeof s === 'number' && Number.isFinite(s));

try { grid.forceUpdate() } catch (e) { if (String(e.message).startsWith('Invalid size returned for cell')) { resetToDefaultSizes(); } else { throw e; } }

When it happens

Trigger: `rowHeight`/`columnHeight` (or cellSizeGetter) returning undefined for an index — e.g. a function that looks up a per-row height array that is shorter than rowCount; returning a non-numeric value; async size lookup without a fallback; size getter reading a record that doesn't exist yet.

Common situations: Passing `rowHeight={({index}) => heights[index]}` where heights isn't yet populated; returning a numeric string that fails after arithmetic; custom size functions with early-return paths that skip the return statement.

Related errors

• Rendered cell should include style property for positioning.
• Invalid metadata returned for cell ${index}: x:${cel
• Unexpected child type registered; only Grid/MultiGrid childr
• Requested index ${index} is outside of range 0..${this._cell

AI-assisted analysis of bvaughn/react-virtualized@c737715486 (2026-08-30). Data as JSON: /api/errors/a029cad62f7594f2. Report an issue: GitHub.