fix(tests): E2E

[sidharthv96]

📑 Summary

Fixes failing E2E tests

Resolves #

📏 Design Decisions

Describe the way your implementation works or what design decisions you made if applicable.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 🔖 targeted develop branch

[sidharthv96]

@knsv making render async has issues like this to handle externally.

[dwhelan]

FWIW, I believe that this will change existing behaviour where currently multiple diagrams load async with each other because render is async.

This change will cause initThrowsError to wait on each diagram to be rendered before the next one. So we could see a performance loss when there are multiple diagrams. It is possible that there is latent race condition in the original code when loading multiple diagrams because there is nothing explicitly waiting for the render promise to resolve AFAIK. Your change fixes that but possibly at the loss of parallel execution.

I think the idiomatic way to handle this would be to change the for loop to map each diagram to its corresponding Promise as returned from render and then use Promise.all to treat them collectively. Something like:

const rendered = nodesToProcess.map( (element) =>  {
    log.info('Rendering diagram: ' + element.id);
    ...      
    return mermaidAPI.render(...);
 }

return Promise.all(rendered);

[sidharthv96]

I don't think render is async, even though it “feels” like it is.

mermaid/packages/mermaid/src/diagrams/flowchart/flowDb.js

Lines 16 to 33 in 9f286b4

	let vertexCounter = 0;
	let config = configApi.getConfig();
	let vertices = {};
	let edges = [];
	let classes = [];
	let subGraphs = [];
	let subGraphLookup = {};
	let tooltips = {};
	let subCount = 0;
	let firstGraphFlag = true;
	let direction;
	let version; // As in graph
	// Functions to be run after graph rendering
	let funs = [];
	const sanitizeText = (txt) => common.sanitizeText(txt, config);

All diagrams use db's with module level state, so you can't render in parallel. (Well, you can, but your diagrams will be rendered wrong).

This is a drawback which should be fixed, but it'll be another MAJOR rewrite.

[sidharthv96]

Related: #3577