[metrics-bugs] #30351 [Metrics/Website]: Unknown error in prepare_* functions using the spread() function

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#30351: Unknown error in prepare_* functions using the spread() function
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     Reporter:  karsten          |      Owner:  metrics-team
         Type:  defect           |     Status:  new
     Priority:  High             |  Milestone:
    Component:  Metrics/Website  |    Version:
     Severity:  Normal           |   Keywords:
Actual Points:                   |  Parent ID:
       Points:                   |   Reviewer:
      Sponsor:                   |
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 This morning we received a [https://lists.torproject.org/pipermail
 /metrics-team/2019-May/001043.html report] that some of the graphs are not
 working anymore.

 Turns out that nine graphs were affected by this issue, all of which using
 the `spread()` function internally. Here's the error message when plotting
 one of these graphs:

 {{{
 Error in get("as_data_frame.matrix", asNamespace("tibble"), mode =
 "function") :
   object 'as_data_frame.matrix' of mode 'function' was not found
 Calls: plot_webstats_tm ... NextMethod -> spread_.data.frame ->
 as_data_frame_matrix -> get
 }}}

 I came up with a hotfix that replaces `spread()` with `cast()`, but that's
 going backwards from the tidyr package to its predecessor, the reshape
 package.

 Also, I didn't find a working fix for the Tor Messenger graph where
 `cast()` works slightly different than `spread()` with regard to missing
 data.

 We'll need to find a better fix. Ideally, we'd find out why `spread()`
 isn't working anymore, including why it stopped working in the first
 place.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30351>
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