`tests.Rraw` 1378.2, 1378.3 fail when the `.Rcheck` directory path contains spaces

[aitap]

mkdir 'code folder'
cd 'code folder'
R CMD check ../data.table_1.18.99.tar.gz

* checking tests ...
 Running ‘main.R’
 ERROR

test.data.table() running: /REDACTED/data.table/code folder/data.table.Rcheck/data.table/tests/tests.Rraw
sh: 1: file:///REDACTED/data.table/code: not found
Test 1378.2 produced 1 warnings but expected 0
Expected: 
Observed: error in running command
Test 1378.2 produced 1 errors but expected 0
Expected: 
Observed: External command failed with exit code 127. This can happen when the disk is full in the temporary directory ('/tmp/RtmpxJGGY8'). See ?fread for the tmpdir argument.
Test 1378.2 produced 1 messages but expected 0
Expected: 
Observed: Taking input= as a system command because it contains a space ('file:///REDACTED/data.table/code folder/data.table.Rcheck/data.table/tests/russellCRLF.csv'). If it's a filename please remove the space, or use file= explicitly. A variable is being passed to input= and when this is taken as a system command there is a security concern if you are creating an app, the app could have a malicious user, and the app is not running in a secure environment; e.g. the app is running as root. Please read item 5 in the NEWS file for v1.11.6 for more information and for the option to suppress this message.

sh: 1: file:///REDACTED/data.table/code: not found
Test 1378.3 produced 1 warnings but expected 0
Expected: 
Observed: error in running command
Test 1378.3 produced 1 errors but expected 0
Expected: 
Observed: External command failed with exit code 127. This can happen when the disk is full in the temporary directory ('/tmp/RtmpxJGGY8'). See ?fread for the tmpdir argument.
Test 1378.3 produced 1 messages but expected 0
Expected: 
Observed: Taking input= as a system command because it contains a space ('file:///REDACTED/data.table/code folder/data.table.Rcheck/data.table/tests/russellCRCRLF.csv'). If it's a filename please remove the space, or use file= explicitly. A variable is being passed to input= and when this is taken as a system command there is a security concern if you are creating an app, the app could have a malicious user, and the app is not running in a secure environment; e.g. the app is running as root. Please read item 5 in the NEWS file for v1.11.6 for more information and for the option to suppress this message.

Originally discovered by @sisyphuswastaken while working on #7543. Should probably use the file=... in the tests.

[MichaelChirico]

Hm, I wonder if the logic should be smarter instead -- fread("file://...") is clearly referring to a file, not a command.

So actually, the test is exposing an actual bug:

library(data.table)
d = file.path(tempdir(), "a dir")
dir.create(d)
f = file.path(d, "a.csv")

fwrite(mtcars, f)
u = sprintf("file://%s", f)
fread(u)

# Taking input= as a system command because it contains a space ('file:///tmp/RtmpyAROdr/a dir/a.csv'). If it's a filename please remove the space, or use file= explicitly. A variable is being passed to input= and when this is taken as a system command there is a security concern if you are creating an app, the app could have a malicious user, and the app is not running in a secure environment; e.g. the app is running as root. Please read item 5 in the NEWS file for v1.11.6 for more information and for the option to suppress this message.
# /bin/sh: line 1: file:///tmp/RtmpyAROdr/a: No such file or directory
# Null data.table (0 rows and 0 cols)
# Warning messages:
# 1: In (if (.Platform$OS.type == "unix") system else shell)(paste0("(", :
# error in running command
# 2: In fread(u) :
# File '/tmp/RtmpyAROdr/file16f89223e0e228' has size 0. Returning a NULL data.table.

# works
download.file(u, tmp<-tempfile())
# works, and fread is not thrown off by the space in 'f'
all.equal(fread(f), fread(tmp))
# [1] TRUE