Stack traces do not render in the dev tools UI when using RStudio's viewer pane #994
Description
RStudio's IDE does not allow embedding of iframe elements which include content from "external" URLs, as noted in rstudio/rstudioapi#2.
The way that dash-renderer currently handles stack traces places them into an iframe so that Werkzeug's CSS doesn't affect the display of the rest of the page:
dash/dash-renderer/src/components/error/FrontEnd/FrontEndError.react.js
Lines 111 to 143 in b3b9de9
This has the unfortunate consequence of showing no stack trace within RStudio, though it appears properly in standalone browsers:
The plot_ly function gets around this problem by embedding source from localhost, which is allowed:
<iframe class="gwt-Frame ace_editor_theme" src="http://localhost:29325/session/viewhtml98b753d4ffc6/index.html?viewer_pane=1" style="width: 100%; height: 100%; position: absolute; left: 0px; top: 0px; right: 0px; bottom: 0px; background-color: rgb(255, 255, 255);"></iframe>
We can preserve the existing behaviour in the renderer for Python apps by implementing a condition which checks whether the content of the stack trace begins with <!DOCTYPE HTML>, then enclose in an iframe if true.
Dash for R would then be modified to send back a stack trace that is raw text, which the renderer will insert directly within <pre> tags (since the above condition would be false), and this should enable support for stack trace display in the RStudio viewer as well as standalone browsers.