Meituan-Dianping/mpvue · error

It seems there are duplicate keys that is causing an update

Error message

It seems there are duplicate keys that is causing an update error. Make sure each v-for item has a unique key.

What it means

Same keyed-diff warning as the core build, emitted by the weex-vue-framework patcher's updateChildren when duplicate/missing v-for keys defeat the key-to-index map and the list diff misbehaves. It indicates list keys are not unique, causing update errors during element reuse.

Source

Thrown at packages/weex-vue-framework/factory.js:5161

        canMove && nodeOps.insertBefore(parentElm, oldStartVnode.elm, nodeOps.nextSibling(oldEndVnode.elm));
        oldStartVnode = oldCh[++oldStartIdx];
        newEndVnode = newCh[--newEndIdx];
      } else if (sameVnode(oldEndVnode, newStartVnode)) { // Vnode moved left
        patchVnode(oldEndVnode, newStartVnode, insertedVnodeQueue);
        canMove && nodeOps.insertBefore(parentElm, oldEndVnode.elm, oldStartVnode.elm);
        oldEndVnode = oldCh[--oldEndIdx];
        newStartVnode = newCh[++newStartIdx];
      } else {
        if (isUndef(oldKeyToIdx)) { oldKeyToIdx = createKeyToOldIdx(oldCh, oldStartIdx, oldEndIdx); }
        idxInOld = isDef(newStartVnode.key) ? oldKeyToIdx[newStartVnode.key] : null;
        if (isUndef(idxInOld)) { // New element
          createElm(newStartVnode, insertedVnodeQueue, parentElm, oldStartVnode.elm);
          newStartVnode = newCh[++newStartIdx];
        } else {
          elmToMove = oldCh[idxInOld];
          /* istanbul ignore if */
          if (process.env.NODE_ENV !== 'production' && !elmToMove) {
            warn(
              'It seems there are duplicate keys that is causing an update error. ' +
              'Make sure each v-for item has a unique key.'
            );
          }
          if (sameVnode(elmToMove, newStartVnode)) {
            patchVnode(elmToMove, newStartVnode, insertedVnodeQueue);
            oldCh[idxInOld] = undefined;
            canMove && nodeOps.insertBefore(parentElm, elmToMove.elm, oldStartVnode.elm);
            newStartVnode = newCh[++newStartIdx];
          } else {
            // same key but different element. treat as new element
            createElm(newStartVnode, insertedVnodeQueue, parentElm, oldStartVnode.elm);
            newStartVnode = newCh[++newStartIdx];
          }
        }
      }
    }
    if (oldStartIdx > oldEndIdx) {

View on GitHub (pinned to 6c5d78ee04)

Solutions

  1. Use a unique stable key per v-for item
  2. Avoid index-based keys on reorderable lists
  3. Sanitize data to remove duplicate identifiers
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at packages/weex-vue-framework/factory.js:5161 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Meituan-Dianping/mpvue@6c5d78ee04 (2026-09-02). Data as JSON: /api/errors/614fce557ae37610. Report an issue: GitHub.