enables loading locales before Plotly

[antoinerg]

This PR enables loading locales before plotly.js is on the page and partially fixes#4146.

In the following Codepens, we expect months to be in French (it should be Mai instead of May):
Before
After

[etpinard]

if(window.PlotlyLocales&&Array.isArray(window.PlotlyLocales)){// ...}

would be safer. Note that Plotly.register([]) is handled correctly (essentially a noop) at the moment.

[antoinerg]

Done in f169380

[etpinard]

This is an interesting solution. I'm not a fan of us polluting the window namespace once more with this new PlotlyLocales global, but I can't really think of a better solution, so 👌

[etpinard]

Maybe we could after this line have:

deletewindow.PlotlyLocales;

to de-pollute the window namespaces after we're done registering the locales.

[antoinerg]

Done in f169380

[archmoj]

Since it is a temporary variable, it may be better to add an underscore i.e. window._PlotlyLocales.

[antoinerg]

Thanks for the suggestion! I'll let @etpinard choose between the different options (see also #4453 (comment))

[archmoj]

Wondering using sessionStorage may be a possibility?

[antoinerg]

This is an interesting solution. I'm not a fan of us polluting the window namespace once more with this new PlotlyLocales global, but I can't really think of a better solution, so

@etpinard Would you prefer me using a locales key in the window.PlotlyConfig object. I know it is used to configure MathJax here.

[etpinard]

Would you prefer me using a locales key in the window.PlotlyConfig object. I know it is used to configure MathJax here.

I forgot about PlotlyConfig. Thanks for pointing this out! Yes, I'd vote for putting your new locales stash in PlotlyConfig.

[alexcjohnson]

Only issue with using PlotlyConfig is if a user includes window.PlotlyConfig = {MathJaxConfig: 'local'} - which is the documented way to support parallel MathJax usage - we'll still have some order-dependent behavior because that will wipe out the locales if they're loaded before the PlotlyConfig script and that script is loaded before plotly.js. I think it'd be better to keep PlotlyConfig reserved for explicitly user-provided behavior. I think window.PlotlyLocales is fine. That said, if we want to be really clever (and hard to debug...) we might even be able to use window.Plotly, as this won't exist yet during the execution of the plotly.js script, right?

[antoinerg]

That's a very good point @alexcjohnson. I reverted b4b20a7 to use window.PlotlyLocales. Should we underscore it or is it OK as it is?

[alexcjohnson]

I'm OK with window.PlotlyLocales, unless anyone feels strongly about the underscore.

[etpinard]

I'm OK with window.PlotlyLocales, unless anyone feels strongly about the underscore.

Yeah, that's fine 👌

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@antoinerg can you merge the latest master into your branch to get the syntax (header) tests to pass?

[etpinard]

Nicely done @antoinerg - 💃 !