build_install_test: use fields in read.dcf to explicitely read the package name

[cstepper]

Hi,

just stumbled across this, as I tried to use build_install_test on a package with a DESCRIPTION file being formatted like this:

Type: Package
Package: jap
Title: Just another package
Version: 0.0.1
...

Running tinytest::build_install_test() locally resulted in the following error:

> tinytest::build_install_test()
* checking for file ‘/home/christoph/packages/jap/DESCRIPTION’ ... OK
* preparing ‘jap’:
* checking DESCRIPTION meta-information ... OK
* cleaning src
* checking for LF line-endings in source and make files and shell scripts
* checking for empty or unneeded directories
* building ‘jap_0.0.1.tar.gz’

Error in library(pkgname, lib.loc = tdir, character.only = TRUE) : 
  there is no package called ‘Package’
Calls: suppressPackageStartupMessages -> withCallingHandlers -> library
Execution halted
Warning in gzfile(file, "rb") :
  cannot open compressed file '/tmp/RtmplJlFgQ/file37c317b5bbcf/output.RDS', probable reason 'No such file or directory'
Error in gzfile(file, "rb") : cannot open the connection
Backtrace:
    █
 1. └─tinytest::build_install_test()
 2.   └─base::readRDS(file.path(tdir, "output.RDS"))
 3.     └─base::gzfile(file, "rb")

I know that the Type field in the DESCRIPTION file is optional. But if it is listed on top, pkgname <- read.dcf(file.path(pkg, "DESCRIPTION"))[1], just returns Package.

To make this more robust, I suggest to rather make use of the fields argument in read.dcf for querying the package name.

[markvanderloo]

Thanks!! good point.