refactor(prepare_genome): drop dead ch_fai intermediate

Author: pinin4fjords

subworkflows/local/prepare_genome_references/main.nf

@@ -185,14 +185,15 @@ workflow PREPARE_GENOME_REFERENCES {
     //-------------------------------------------------------
     // 7) FAI / chrom.sizes only if we actually have a genome
     //-------------------------------------------------------
-    ch_fai         = channel.empty()
     ch_fasta_fai   = channel.empty()
     ch_chrom_sizes = channel.empty()
     if (fasta_provided) {
         SAMTOOLS_FAIDX(ch_fasta.map { item -> [ [:], item, [] ] }, true)
-        ch_fai         = SAMTOOLS_FAIDX.out.fai.map { tuple -> tuple[1] }
         ch_chrom_sizes = SAMTOOLS_FAIDX.out.sizes.map { tuple -> tuple[1] }
-        ch_fasta_fai   = ch_fasta.combine(ch_fai).map { fasta_file, fai_file -> [ [:], fasta_file, fai_file ] }.first()
+        ch_fasta_fai   = ch_fasta
+            .combine(SAMTOOLS_FAIDX.out.fai.map { _meta, fai_file -> fai_file })
+            .map { fasta_file, fai_file -> [ [:], fasta_file, fai_file ] }
+            .first()
     }
 
     //-------------------------------------------------------------