Galata's setCell helper does not work reliably

[krassowski]

Description

As seen in #15171 galata's setCell helper does not always set cell content correctly. This was also seen in other, older pull requests. A temporary workaround of calling it twice was introduced in fb079b7 which works but is hinting at some problem.

The problematic runs locally exhibited an odd behaviour of switching the code cell type to raw even though this was never requested. It might be that the problem is not in setCell but in setCellType which is the first call of the former:

jupyterlab/galata/src/helpers/notebook.ts

Lines 1053 to 1094 in 2ff6899

	/**
	* Set the input source of a cell
	*
	* @param cellIndex Cell index
	* @param cellType Cell type
	* @param source Source
	* @returns Action success status
	*/
	async setCell(
	cellIndex: number,
	cellType: nbformat.CellType,
	source: string
	): Promise<boolean> {
	if (!(await this.isAnyActive())) {
	return false;
	}
	await this.setCellType(cellIndex, cellType);
	if (
	!(await this.isCellSelected(cellIndex)) &&
	!(await this.selectCells(cellIndex))
	) {
	return false;
	}
	await this.enterCellEditingMode(cellIndex);
	const keyboard = this.page.keyboard;
	await keyboard.press('Control+A');
	// give CodeMirror time to style properly
	await keyboard.type(source, { delay: cellType === 'code' ? 100 : 0 });
	await this.leaveCellEditingMode(cellIndex);
	// give CodeMirror time to style properly
	if (cellType === 'code') {
	await this.page.waitForTimeout(500);
	}
	return true;
	}

Further, from debugging with playwright it seemed that it could have been due to the notebook in panel not being returned at the first attempt leading to incorrect result of cell type null on getCellType check:

jupyterlab/galata/src/helpers/notebook.ts

Lines 1103 to 1112 in 2ff6899

	async setCellType(
	cellIndex: number,
	cellType: nbformat.CellType
	): Promise<boolean> {
	const nbPanel = await this.activity.getPanel();
	if (!nbPanel) {
	return false;
	}
	if ((await this.getCellType(cellIndex)) === cellType) {

jupyterlab/galata/src/helpers/notebook.ts

Lines 1147 to 1151 in 2ff6899

	async getCellType(cellIndex: number): Promise<nbformat.CellType | null> {
	const notebook = await this.getNotebookInPanel();
	if (!notebook) {
	return null;
	}

but I am not sure if the runs with instrumentation were representative of what is happening without it.

JupyterLab main head 4.1.0a1

[fcollonval]

Thanks for digging this one up Mike. I agree on your conclusion that unfortunately instrumentation introduces biases.

[krassowski]

I think this is no longer a problem after recent refactors.