getParseData returns NULL within testthat

Question

I am trying to extract the SYMBOLs from a string that represents code using the getParseData() function. The code works when I run it in my normal session, but when I run it in a testthat::test_that it fails and returns a NULL.

Furthermore, when I execute the examples of getParseData(), I also get a NULL and not the expected parsed data.

E.g.

# from ?getParseData
fn <- function(x) {
  x + 1 # A comment, kept as part of the source
}

getParseData(fn)
#> NULL
# I would expect a data.frame here!

Note that when I click "Run Examples" in the RStudio helper tab, the expected result is shown...

Or with code as string (my main use case)

# this is what I expect; works when I execute it directly
getParseData(parse(text = code))
#>   line1 col1 line2 col2 id parent     token terminal text
#> 7     1    1     1    8  7      0      expr    FALSE     
#> 1     1    1     1    3  1      3    SYMBOL     TRUE  mpg
#> 3     1    1     1    3  3      7      expr    FALSE     
#> 2     1    5     1    5  2      7        GT     TRUE    >
#> 4     1    7     1    8  4      5 NUM_CONST     TRUE   10
#> 5     1    7     1    8  5      7      expr    FALSE

Similarly, when I use this in a testthat case

test_that("getPaseData", {

  code <- "mpg > 10"

  print("getParseData(parse(text = code))")
  print(getParseData(parse(text = code))) # for debugging
  expect_equal(class(getParseData(parse(text = code))), "data.frame")
})

The tests pass when I call the code directly, but when I click on "Run Tests" in RStudio it fails with NULL.

(eg in the picture below the purple arrows show what happens when I click RUN TESTS and it fails; the green arrow shows that the tests pass when I run it from the console.

Any idea what causes this?

getParseData returns NULL within testthat

Answers (1)

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