Preserve empty lines in snapshot output

[hadley]

Fixes #1509

[hadley]

The root cause is that some conditions implicitly add a trailing new line, and some implicitly swallow a trailing new line. This now matches the behaviour I see on the console.

[gaborcsardi]

FWIW this PR does not fix the test cases in cli. After removing the temporary cli::expect_snapshot() helper function now I get:

testthat::test_local(filter = "contain")

✔ | F W S  OK | Context
✖ | 1       6 | containers [0.3s]
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Failure (test-containers.R:78:3): margin is squashed
Snapshot of code has changed:
     old                 | new
[23] "  "                | "  "                [23]
[24] "  "                | "  "                [24]
[25] "  "                | "  "                [25]
[26] "  until here"      - "  "                [26]
[27] "  "                - "  until here"      [27]
[28] "  "                | "  "                [28]
[29] "  "                | "  "                [29]
[30] "  no space, still" - "  "                [30]
[31] "  "                | "  "                [31]
[32] "  "                - "  no space, still" [32]
 ... ...                   ...                 and 5 more ...

Run `snapshot_accept('containers')` if this is a deliberate change

Is this expected?

[hadley]

@gaborcsardi do you mind boiling that down to a more minimal reprex? I find it hard to reason about exactly what should occur given all the \r.

[gaborcsardi]

This test was actually not broken in version 3.1.1, but this PR breaks it. It is not about \r but messages that consist of only \n characters.

Example

library(testthat)
testthat::test_that("snapshots and whitespace", {
  local_edition(3)
  msgs <- list("start\n", "\n\n", "until here\n", "\n\n",
    "still\n", "\n\n", "again\n")
  expect_snapshot(local({
    for (m in msgs) message(m, domain = NA, appendLF = FALSE)
  }))
})

testthat 3.1.1 output

i Current value:
Code
  local({
    for (m in msgs) message(m, domain = NA, appendLF = FALSE)
  })
Message <simpleMessage>
  start

  until here

  still

  again

testthat #1524 output

i Current value:
Code
  local({
    for (m in msgs) message(m, domain = NA, appendLF = FALSE)
  })
Message <simpleMessage>
  start


  until here


  still


  again

[hadley]

I think this PR is correct, because when I run this at the console I see:

start


until here


still


again

But I think evaluate or knitr gets it wrong because this is the reprex:

msgs <- list("start\n", "\n\n", "until here\n", "\n\n",
             "still\n", "\n\n", "again\n")
local({
  for (m in msgs) message(m, domain = NA, appendLF = FALSE)
})
#> start
#> 
#> until here
#> 
#> still
#> 
#> again

^{Created on 2022-01-05 by the reprex package (v2.0.1)}

[hadley]

i.e. this is wrong:

msgs <- c("line 1", "\n", "line 4")
local({
  for (m in msgs) message(m)
})
#> line 1
#> 
#> line 4

^{Created on 2022-01-05 by the reprex package (v2.0.1)}