plotly_POST not embedding plot as expected

[solarchemist]

So this is a little weird, and I haven't been able to figure it out after reading the documentation (1, 2, 3, 4).

I generated a plot using ggplot2, which I then embed in a R Markdown document published as HTML on the web (Jekyll blog, but that's beside the point).

```{r lnb-160411-quality-fits, echo=FALSE, results="asis"}
p <- ggplot() + ...
plotly_POST(p, filename = "lnb-160411-poor-fits", fileopt = "overwrite", sharing = "public")

This produces the following HTML:

<iframe src="https://plot.ly/~chepec/151" width="800" height="600" id="igraph" scrolling="no" seamless="seamless" frameBorder="0">
</iframe>

Which does not produce the expected result, i.e., an embedded plot, but instead embeds the entire Plotly page (see below).

I confirmed that the URL in the iframe above is in fact the output of plotly_POST,

> x <- plotly_POST(p, filename = "lnb-160411-poor-fits", fileopt = "overwrite", sharing = "public")
No encoding supplied: defaulting to UTF-8.
Success! Modified your plotly here -> https://plot.ly/~chepec/151
> str(x)
List of 5
 $ url     : chr "https://plot.ly/~chepec/151"
 $ message : chr ""
 $ warning : chr ""
 $ filename: chr "lnb-160411-poor-fits"
 $ error   : chr ""
 - attr(*, "class")= chr "figure"

and I think I can confirm that Plotly shows the embed only when appending .embed to the URL (the HTML below produces the expected embedded plot):

<iframe src="https://plot.ly/~chepec/151.embed" width="800" height="600" id="igraph" scrolling="no" seamless="seamless" frameBorder="0">
</iframe>

I think this must be an issue with plotly_POST? It should return the URL of an embed plot, not the whole page. By the way, this behaviour must have changed quite recently because the very same plotly_POST(...) call produced a properly embedded plot just a month ago.

[cpsievert]

Thanks!!