Leiningen engine fails to knit without additional plugin

[phillc73]

engine.R indicates that Clojure is supported through the Leiningen REPL

else paste(switch(
    engine, bash = '-c', coffee = '-e', groovy = '-e', lein = 'exec -e',
    mysql = '-e', node = '-e', perl = '-e', psql = '-c', python = '-c',
    ruby = '-e', scala = '-e', sh = '-c', zsh = '-c', NULL
  ), shQuote(paste(options$code, collapse = '\n')))

There is also a pull request in the knitr-examples repository with a Clojure example.

Unfortunately, knitting the example fails.

Error generated is:

processing file: test.Rmd
  |.......                                                          |  11%
  ordinary text without R code

  |..............                                                   |  22%
label: setup (with options) 
List of 1
 $ include: logi FALSE

  |......................                                           |  33%
  ordinary text without R code

  |.............................                                    |  44%
label: unnamed-chunk-1 (with options) 
List of 1
 $ engine: chr "lein"

running: lein  exec -e '(def x "Hello world!")
(println x)'

Quitting from lines 11-13 (test.Rmd) 
Error in engine(options) : 'exec' is not a task. See 'lein help'.

Did you mean this?
         new
         check
Calls: <Anonymous> ... process_group.block -> call_block -> block_exec -> in_dir -> engine
In addition: Warning message:
running command ''lein'  exec -e '(def x "Hello world!")
(println x)' 2>&1' had status 1 
Execution halted

Leiningen is in basic default configuration and the version information is:

Leiningen 2.6.1 on Java 1.8.0_72-internal OpenJDK 64-Bit Server VM

To fix this problem, the lein-exec plugin must be added to the leiningen ~/.lein/profiles.clj file:

{:user {:plugins [[lein-exec "0.3.6"]]}}

Once this is added, the example code chunk renders.

I didn't find this information anywhere else in knitr documentation, and I'm not sure where it should or could be added.

[yihui]

Yeah I guess it should be documented. I know nothing about Clojure, though. Thanks!

[github-actions]

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