Factor parsing is incorrect when escaping backslashes

[mllg]

In the following example, the first escaped quote disappears in the first column. I expected to maybe get an error here because I've not set escape_backslash:

Even worse, the "A" in the first row now is a "B". 😟

path = tempfile()

writeLines(c(
  "'\\'A\\'',T",
  "'\\'B\\'',F"
), con = path)
vroom::vroom(path, col_names = c("x", "y"), col_types = list(vroom::col_factor(), vroom::col_factor()), quote = "'")

# A tibble: 2 x 2
  x        y
  <fct>    <fct>
1 "\\B\\'" T
2 "\\B\\'" F

The later also happens with escapse_backslash:

vroom::vroom(path, col_names = c("x", "y"), col_types = list(vroom::col_factor(), vroom::col_factor()), quote = "'", escape_backslash = TRUE)

# A tibble: 2 x 2
  x     y
  <fct> <fct>
1 'B'   F
2 'B'   F

Another example without escapes:

writeLines(c(
  "''A'',T",
  "''B'',F"
), con = path)
vroom::vroom(path, col_names = c("x", "y"), col_types = list(vroom::col_factor(), vroom::col_factor()), quote = "'", escape_backslash = TRUE)

# A tibble: 2 x 2
  x     y
  <fct> <fct>
1 B'    F
2 B'    F

> sessionInfo()
R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Arch Linux

Matrix products: default
BLAS/LAPACK: /usr/lib/libopenblas_haswellp-r0.3.6.so

locale:
 [1] LC_CTYPE=de_DE.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8     LC_MONETARY=en_US.UTF-8
 [6] LC_MESSAGES=de_DE.UTF-8    LC_PAPER=de_DE.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=de_DE.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] nvimcom_0.9-83    gtfo_0.0.0.9000   data.table_1.12.4

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.2       fansi_0.4.0      assertthat_0.2.1 utf8_1.1.4       crayon_1.3.4     withr_2.1.2      magrittr_1.5     pillar_1.4.2     cli_1.1.0
[10] rlang_0.4.0      vroom_1.0.2      tools_3.6.1      glue_1.3.1       purrr_0.3.2      parallel_3.6.1   compiler_3.6.1   pkgconfig_2.0.3  tidyselect_0.2.5
[19] tibble_2.1.3

[mllg]

Seems like it is not related to quotes, this also reads in the data incorrectly:

path = tempfile()
writeLines(c(
  "A,T",
  "B,F"
), con = path)
vroom::vroom(path, col_names = c("x", "y"), col_types = list(vroom::col_factor(), vroom::col_factor()), escape_backslash = TRUE)

# A tibble: 2 x 2
  x     y
  <fct> <fct>
1 B     F
2 B     F

There are duplicated factor levels:

Classes 'tbl_df', 'tbl' and 'data.frame':       2 obs. of  2 variables:
 $ x: Factor w/ 2 levels "B","B": 1 2
 $ y: Factor w/ 2 levels "F","F": 1 2
 - attr(*, "spec")=
  .. cols(
  ..   x = col_factor(levels = NULL, ordered = FALSE, include_na = FALSE),
  ..   y = col_factor(levels = NULL, ordered = FALSE, include_na = FALSE)
  .. )

[jimhester]

A minimal reprex is

vroom::vroom("A,T\nB,F\n", col_names = FALSE, col_types = list("f", "f"), escape_backslash = TRUE)
#> # A tibble: 2 x 2
#>   X1    X2   
#>   <fct> <fct>
#> 1 B     F    
#> 2 B     F
vroom::vroom("A,T\nB,F\n", col_names = FALSE, col_types = list("f", "f"), escape_backslash = FALSE)
#> # A tibble: 2 x 2
#>   X1    X2   
#>   <fct> <fct>
#> 1 A     T    
#> 2 B     F

^{Created on 2019-10-14 by the reprex package (v0.3.0)}