English locales are refused by `config()`

[salim-b]

When trying to set a plot's locale to one of "en", "en-US" or "en-GB", an error is thrown. But according to the documentation, at least "en" and "en-US" should be valid locales!

I know that English is the default locale. But right now changing a plot's locale from the default EN to something else is kind of a "one way road":

library(magrittr)

plotly::plot_ly(data = iris,
                x = ~Sepal.Length,
                y = ~Petal.Length) %>%
    plotly::config(locale = "de-CH") %>%
    plotly::config(locale = "en-US")
#> Error: Invalid locale: 'en-US'.
#> 
#> Supported locales include: 'af', 'am', 'ar-dz', 'ar-eg', 'ar', 'az', 'bg', 'bs', 'ca', 'cs', 'cy', 'da', 'de-ch', 'de', 'el', 'eo', 'es-ar', 'es', 'es-pe', 'et', 'eu', 'fa', 'fi', 'fo', 'fr-ch', 'fr', 'gl', 'gu', 'he', 'hi-in', 'hr', 'hu', 'hy', 'id', 'is', 'it', 'ja', 'ka', 'km', 'ko', 'lt', 'lv', 'me', 'me-me', 'mk', 'ml', 'ms', 'mt', 'nl-be', 'nl', 'no', 'pa', 'pl', 'pt-br', 'rm', 'ro', 'ru', 'sk', 'sl', 'sq', 'sr', 'sr-sr', 'sv', 'sw', 'ta', 'th', 'tr', 'tt', 'uk', 'ur', 'vi', 'zh-cn', 'zh-hk', 'zh-tw'

^{Created on 2020-01-23 by the reprex package (v0.3.0)}

This is because the available locales are determined by this code:

sub("\\.js$", "", list.files(system.file(plotly:::dependency_dir("plotlyjs", "locales"), 
                                         package = "plotly")))
#>  [1] "af"    "am"    "ar-dz" "ar-eg" "ar"    "az"    "bg"    "bs"    "ca"   
#> [10] "cs"    "cy"    "da"    "de-ch" "de"    "el"    "eo"    "es-ar" "es"   
#> [19] "es-pe" "et"    "eu"    "fa"    "fi"    "fo"    "fr-ch" "fr"    "gl"   
#> [28] "gu"    "he"    "hi-in" "hr"    "hu"    "hy"    "id"    "is"    "it"   
#> [37] "ja"    "ka"    "km"    "ko"    "lt"    "lv"    "me"    "me-me" "mk"   
#> [46] "ml"    "ms"    "mt"    "nl-be" "nl"    "no"    "pa"    "pl"    "pt-br"
#> [55] "rm"    "ro"    "ru"    "sk"    "sl"    "sq"    "sr"    "sr-sr" "sv"   
#> [64] "sw"    "ta"    "th"    "tr"    "tt"    "uk"    "ur"    "vi"    "zh-cn"
#> [73] "zh-hk" "zh-tw"

^{Created on 2020-01-23 by the reprex package (v0.3.0)}

Obviously, the English strings aren't defined in separate .js files inside the directory htmlwidgets/lib/plotlyjs/locales (relative to the plotly R package path). So I think there should be a proper exception added for EN locales in R/layout.R:

https://github.com/ropensci/plotly/blob/c47c1f957f1783d6212842463b0722c9473093b7/R/layout.R#L136-L142