[Bioc-devel] VariantAnnotation::readVcf(fl, seqinfo(scanVcfHeader(fl)) problem

hi there,

in my package VariantFiltering i have an example VCF file from a Hapmap
CEU trio including three chromosomes only to illustrate its vignette.
i've come across a problem with the function readVcf() in
VariantAnnotation that may be specific of the situation of a VCF file
not having all chromosomes, but which it will be great for me if this
could be addressed.

the problem is reproduced as follows:

===========================
library(VariantAnnotation)

fl <- file.path(system.file("extdata", package="VariantFiltering"),
"CEUtrio.vcf.bgz")

vcf <- readVcf(fl, seqinfo(scanVcfHeader(fl)))
Error in GenomeInfoDb:::makeNewSeqnames(x, new2old = new2old,
seqlevels(value)) :
   when 'new2old' is NULL, the first elements in the
   supplied 'seqlevels' must be identical to 'seqlevels(x)'
====================

this is caused because although i'm providing the Seqinfo object derived
from the header of the VCF file itself, at some point the ordering of
the seqlevels between the header and the rest of the VCF file differs
due to the smaller subset of chromosomes in the VCF file.

This can be easily fixed by replacing the line:

                 if (length(newsi) > length(oldsi)) {

within the .scanVcfToVCF() function in methods-readVcf.R, by

                 if (length(newsi) >= length(oldsi)) {

this is happening both in release and devel. i'm pasting below my
sessionInfo() for the release.

let me know if you think this fix is feasible or i'm wrongly using the
function readVcf(). i'm basically trying to use readVcf() without having
to figure out the appropriate value for the argument 'genome', i.e.,
without knowing beforehand what version of the genome was used to
produce the VCF file.

thanks!!
robert.


sessionInfo()
R version 3.1.1 Patched (2014-10-13 r66751)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
  [1] LC_CTYPE=en_US.UTF8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF8        LC_COLLATE=en_US.UTF8
  [5] LC_MONETARY=en_US.UTF8    LC_MESSAGES=en_US.UTF8
  [7] LC_PAPER=en_US.UTF8       LC_NAME=C
  [9] LC_ADDRESS=C              LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF8 LC_IDENTIFICATION=C

attached base packages:
[1] stats4    parallel  stats     graphics  grDevices
[6] utils     datasets  methods   base

other attached packages:
  [1] VariantAnnotation_1.12.0 Rsamtools_1.18.0
  [3] Biostrings_2.34.0        XVector_0.6.0
  [5] GenomicRanges_1.18.0     GenomeInfoDb_1.2.0
  [7] IRanges_2.0.0            S4Vectors_0.4.0
  [9] BiocGenerics_0.12.0      vimcom_1.0-0
[11] setwidth_1.0-3           colorout_1.0-3

loaded via a namespace (and not attached):
  [1] AnnotationDbi_1.28.0    base64enc_0.1-2
  [3] BatchJobs_1.4           BBmisc_1.7
  [5] Biobase_2.26.0          BiocParallel_1.0.0
  [7] biomaRt_2.22.0          bitops_1.0-6
  [9] brew_1.0-6              BSgenome_1.34.0
[11] checkmate_1.4           codetools_0.2-9
[13] DBI_0.3.1               digest_0.6.4
[15] fail_1.2                foreach_1.4.2
[17] GenomicAlignments_1.2.0 GenomicFeatures_1.18.0
[19] iterators_1.0.7         RCurl_1.95-4.3
[21] RSQLite_0.11.4          rtracklayer_1.26.0
[23] sendmailR_1.2-1         stringr_0.6.2
[25] tools_3.1.1             XML_3.98-1.1
[27] zlibbioc_1.12.0