Explicitly set Cytoscape's elements default values, fix interactions test

[xhluca]

About

This fixes the problem where creating a cyto.Cytoscape() without specifying elements would throw an error.

Description of changes

Pre-Merge checklist

• The project was correctly built with npm run build:all.
• If there was any conflict, it was solved correctly
• All changes were documented in CHANGELOG.md.
• All tests on CircleCI have passed.
• All Percy visual changes have been approved.
• Two people have 💃'd the pull request. You can be one of these people if you are a Dash Cytoscape core contributor.

Reference Issues

Closes #61

Other comments

[alexcjohnson]

Not []?

[alexcjohnson]

Both {} and [] are fine since 0.1, so I don't think it matters a lot.

Not according to the propType:

dash-cytoscape/src/lib/components/Cytoscape.react.js

Line 534 in 4cba5bc

elements: PropTypes.arrayOf(PropTypes.object),

So either we should change this to something like

elements: PropTypes.oneOfType([PropTypes.arrayOf(PropTypes.object), PropTypes.object])

Or we should change the default to []

[xhluca]

Good catch. I'll update the proptypes.

[xhluca]

Both {} and [] are fine since 0.1, so I don't think it matters a lot.

…

On Mon, Jul 6, 2020, 3:27 PM alexcjohnson ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In src/lib/components/Cytoscape.react.js <#96 (comment)>: > @@ -818,7 +818,8 @@ Cytoscape.defaultProps = { autoRefreshLayout: true, generateImage: {}, imageData: null, - responsive: false + responsive: false, + elements: {} Not []? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#96 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFBTAWMIXW74NXUSONYA7UDR2IQQ3ANCNFSM4OQCXMHQ> .

[xhluca]

By the way, this is the PR that added support for {}: plotly/react-cytoscapejs#2

Re-reading that PR, i realize that perhaps setting [] as default is a good idea, since {} is not the "preferred" way to define empty elements. Furthermore, we might end up going into a use case like:

app.callback(Output('cytoscape', 'elements'), Input('dropdown', 'value'), [State('cytoscape', 'elements'])
def add_new_node(elements):
  node = ...
  elements.append(node)
  return elements

in which case initializing an empty cytoscape graph with {} might pose problem.

[alexcjohnson]

in which case initializing an empty cytoscape graph with {} might pose problem.

Default prop values don't come back in callbacks, so I think for a use case like this you'll still need to do something like return (elements or []) + [node]. But I agree that the default should reflect the preferred syntax.

[alexcjohnson]

I haven't looked into the test failures, but assuming those get sorted out this looks good to me. 💃