invalidation of Jupyter notebook cells

invalidation.js

// Find deepest DOM ancestor that does not change on reexecute
const findParentOutputDiv = (el) => {
    let candidate = el;
    while (candidate) {
        candidate = candidate.parentElement
        if (candidate.className === 'output') {
            return candidate;
        }
    }
    throw Error("parent output div not found");
}

// Find shallowest DOM ancestor that is removed on delete
const findParentCell = (el) => {
        let candidate = el;
        while (candidate) {
            candidate = candidate.parentElement
            if (candidate.classList.contains('cell')) {
                return candidate;
            }
        }
        throw Error("cell not found not found");
    }

const onCellReexecuteOrDelete = (element, cb) => {
    
    const outputDiv = findParentOutputDiv(element);
    const cellDiv = findParentCell(element);
    const notebookContainer = cellDiv.parentElement;
    let onEither = () => { throw Error('callback not initialized yet'); }

    const reexecuteDetector = function(mutationsList, observer) {
        for(let mutation of mutationsList) {
            if (mutation.type === 'childList') {
                onEither('cell reexecute');
                return;
            }
        }
    };
    
    const cellDeleteDetector = function(mutationsList, observer) {
        for (let mutation of mutationsList) {
            if (mutation.type === 'childList') {
                for (let node of mutation.removedNodes) {
                    if (node === cellDiv) {
                        onEither('cell delete')
                        return;
                    }
                }

            }
        }
    };

    const outputMutationObserver =  new MutationObserver(reexecuteDetector);
    const notebookMutationObserver = new MutationObserver(cellDeleteDetector);
    
    onEither = (reason) => {
        outputMutationObserver.disconnect();
        notebookMutationObserver.disconnect();
        cb(reason);
    }
    
    outputMutationObserver.observe(outputDiv, { childList: true });
    notebookMutationObserver.observe(notebookContainer, { childList: true });
}

window.onCellReexecuteOrDelete = onCellReexecuteOrDelete;