feat: add --outSAMattrRGline with @RG header and RG:Z tags#6
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Parses STAR's comma-separated multi-RG syntax (first field must be ID: on each block, `,` separates blocks, tokens are tab-joined into the SAM @rg body). Replicates a single RG line across N input files like STAR does, and errors on count mismatch or RG-in-outSAMattributes without a line. Auto-appends RG to sam_attribute_set() when a line is set (matches Parameters_samAttributes.cpp:201). SAM/BAM headers now emit one @rg per unique ID, and every record (mapped, unmapped, half-mapped, both- mates) carries RG:Z:<id> when attrs contain RG. Unblocks nf-core/rnaseq, which invokes STAR with `--outSAMattrRGline 'ID:X' 'SM:X'` and previously errored on the unknown flag. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
- Remove the `let _ = params.rg_ids()?;` early-validation line in
`align_reads_paired_end`. `validate()` already calls `rg_ids()` at
startup, so the second call was a no-op.
- Simplify `maybe_insert_rg_tag` to `(record, rg_id)` by dropping the
`attrs: &HashSet<String>` parameter and its `attrs.contains("RG")`
gate. `sam_attribute_set()` auto-inserts "RG" whenever an RG line is
configured, so `rg_id.is_some()` already implies the tag is wanted.
- Replace the inline `if let Some(id) = rg_id { ... }` block in
`build_unmapped_record` with a call to the simplified helper, so every
writer-side RG insertion goes through the same path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Add `Parameters::primary_rg_id() -> Result<Option<String>, Error>` that returns the first RG line's `ID:` value directly, and use it to replace the `let rg_ids = params.rg_ids()?; let rg_id = rg_ids.first()...` two-step pattern at every SAM/BAM writer callsite (5 in sam.rs, 1 in lib.rs). `rg_ids()` is retained because `validate()` still uses it for the 1-vs-N count check against `--readFilesIn`. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Replace the manual `while i < len` index-walk with a `out_sam_attr_rg_line.split(|tok| tok == ",")` that maps each block to its tab-joined body and propagates any `ID:`-prefix error via `collect::<Result<_,_>>()`. Same public signature and return value as before, but with half the local state. Behavior note: an empty block (adjacent `,`s or a trailing `,`) now returns a `Parameter` error instead of being silently skipped. This matches STAR's `Parameters_readFilesInit.cpp` which requires every RG block to begin with `ID:`. Existing tests still pass. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
`SamWriter::write_unmapped` had no production callers — the SE/PE write paths build unmapped records via `build_unmapped_record` and batch them through `write_batch`. The only caller was the method's own self-test. Delete both. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Fixes formatting drift inherited from main. No semantic changes. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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--outSAMattrRGline with @RG header and RG:Z tags
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Apr 24, 2026
- shuffle_tied_prefix: deterministic per-read RNG for tied primary selection - --runRNGseed param (default 777, matches STAR) - --outSAMattrRGline: @rg header + RG:Z tags - Various code simplifications and formatting
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Summary
Adds the
--outSAMattrRGlineCLI flag, emits@RGlines in the SAM header, and tags every record withRG:Z:<ID>. Matches STAR's semantics (Parameters_readFilesInit.cpp:65-93,samHeaders.cpp,ReadAlign_alignBAM.cpp:333).Part 2 of 3 branches unblocking nf-core/rnaseq's STAR_ALIGN step. Standalone PR; does not depend on the others.
Changes
src/params.rs:out_sam_attr_rg_line: Vec<String>arg +parsed_rg_lines()/rg_ids()/rg_line_set()helpers. STAR's comma-separated multi-RG syntax supported. Auto-appendsRGtosam_attribute_set()when a line is set;validate()errors onRGin attrs without a line (matches STAR).src/io/sam.rs:build_sam_header()now emits@RGlines (deduplicated by ID). Newmaybe_insert_rg_tag()helper insertsRG:Z:<id>on every record (main, mate2, half-mapped, unmapped).src/io/bam.rs: call-site updates for the new signatures.src/lib.rs: computes RG ID once per run; passes through SE and PE paths.Design note
The RG tag is inserted post-build via
maybe_insert_rg_tag()rather than threaded through every builder signature. Same output, less churn.Follow-up commits
attrsgate onmaybe_insert_rg_tag; addParameters::primary_rg_idhelper to replace a recurring allocation pattern; rewriteparsed_rg_lines()usingVec::split; remove deadSamWriter::write_unmappedmethod.cargo fmtcommit to fix pre-existing drift inherited frommain.Test plan
cargo test— 286 unit + 4 integration (−1 from removing the self-test of the deleted dead code)cargo clippy --lib -- -D warnings— cleancargo fmt --check— clean@RG+RG:Z:viasamtools view -Handsamtools view | grep RG:Z:)Notes
parsed_rg_lines()now errors on "empty block after trailing comma" instead of silently skipping. Stricter, matches STAR.🤖 Generated with Claude Code