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feat(protein): add the protein subcommand and its sequence mode - #158

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BenjaminDEMAILLE:feat/protein-skeleton
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feat(protein): add the protein subcommand and its sequence mode#158
BenjaminDEMAILLE wants to merge 23 commits into
seqeralabs:mainfrom
BenjaminDEMAILLE:feat/protein-skeleton

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@BenjaminDEMAILLE BenjaminDEMAILLE commented Aug 28, 2026

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Part of #163.

First of a protein QC series. Stacked on #156, the tip of the DNA stack, because it reuses src/common from #152.

Adds rustqc protein sequence: protein FASTA quality control.

Parity against seqkit 2.13.0

The statistics table reproduces seqkit stats -a -T byte for byte on both fixtures, two small real protein FASTA files from nf-core/test-datasets totalling 16 kB.

Two of seqkit's conventions had to be recovered from its behaviour, and neither is what a statistics library gives you by default:

Quartiles are Tukey's halves. Q1 is the median of the lower half of the sorted lengths, not an interpolated value. On the yeast fixture that is 157, where linear interpolation gives 165 and inverse-ECDF agrees on Q1 but then disagrees on Q2.

Those halves round half-to-even. A median of 235.5 is reported as 236, but 376.5 and 516.5 are reported as 376 and 516. Ordinary rounding gets the first right and the other two wrong, which is exactly the kind of near-miss that looks like a passing test on one file.

Beyond seqkit

seqkit answers "how long are these sequences". The report answers "is this proteome usable":

  • per-residue composition, with the fractions summing to one over every residue seen;
  • stop codons anywhere but the final position, which truncate the protein;
  • residues that are not amino acids, reported once per sequence with the first offender;
  • byte-identical duplicate sequences, paired with the identifier they duplicate;
  • identifiers reused for different sequences.

Ambiguity codes (B, Z, J, X) are counted rather than flagged, since they are valid. Selenocysteine and pyrrolysine are treated as standard residues, because translated proteomes carry them.

Command shape

The subcommand takes an explicit mode:

rustqc protein sequence <FASTA>...

rather than inferring one from which flags were given. Two further modes are planned, coding (BAM plus GTF) and spectra (mzML), and they take entirely different inputs; a flat command would need a validation matrix explaining which flag applies when. Only sequence exists so far, and rustqc protein <file> is rejected rather than silently guessing.

Shared options keep the names, short flags and RUSTQC_* environment variables they have in rna and dna.

Tests

385 green, up from 353. Six are protein parity tests; the rest are unit tests over the parsing, the statistics conventions and each defect category.

🤖 Generated with Claude Code

BenjaminDEMAILLE and others added 22 commits August 28, 2026 18:26
These three modules carry no RNA-specific logic and are needed by the
forthcoming dna subcommand. src/rna re-exports them so every existing
crate::rna::... path and the published 0.2.x library surface keep working.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
bam_stat is read-level and needs no annotation, and the samtools stats,
flagstat and idxstats writers consume its result type, so all four move
together into src/common/. src/rna/rseqc re-exports them.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
BamStatAccum gathers the read-level counters behind bam_stat and the
samtools writers. Its process_read takes only a record and a MAPQ cutoff,
so it is assay-agnostic and the dna pipeline will drive the same struct.
The merge_vec_arrays helper moves with it, being its only consumer.
rna::rseqc::accumulators re-exports the type.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Also corrects the AGENTS.md claim that the crate has no lib.rs, which has
been untrue since seqeralabs#101.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
A real public human chr22 slice from nf-core/test-datasets, duplicate-marked
locally with samtools, plus mosdepth 0.3.14 and samtools 1.24 reference
outputs. The generation script pins both tool versions and refuses to run
against others, so fixtures and tool versions cannot drift apart.

380 kB in total, well inside the 10 MB fixture budget.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Shared options keep the same long name, short flag and RUSTQC_* environment
variable as their rna counterparts. The deliberate differences: no --gtf, no
--stranded, and --mapq defaults to 0 rather than 30 because that is
mosdepth's default.

run_dna is a stub for now; the pipeline lands in the following commits.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Config gains a `dna` block alongside `rna`, with mosdepth and samtools
sub-sections and a reuse of the existing PreseqConfig. Shared settings
(chromosome_prefix, chromosome_mapping, sample_name, flat_output) are
declared on DnaConfig itself, mirroring RnaConfig, so the two pipelines
can be configured independently in one file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
DepthAccum records aligned blocks as increments in a delta array the length
of the contig, then a prefix sum turns that into per-base depth in one linear
pass. Filters and CIGAR handling reproduce mosdepth 0.3.14 outside fast mode:
flags 1796 excluded, MAPQ floor applied, M/=/X cover the reference, D/N
advance without covering, and I/S/H/P do not advance.

Mate-overlap correction, the other half of mosdepth's default behaviour,
lands in the next commit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
mosdepth counts a base once when both mates of a pair cover it, unless
--fast-mode is given. On the test dataset this is the difference between
469875 and 247878 total covered bases, so it is the dominant behaviour
rather than an edge case.

Pending mates are held in a map keyed by read name, indexed by the position
the outstanding mate was announced at so entries that can never be claimed
are evicted as the coordinate-ordered scan moves past them. A test asserts
the map empties.

Includes an engine-level parity check against the committed mosdepth
fixture: total covered bases and maximum depth both match exactly.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Six writers plus the per-contig summarisation that feeds them: summary,
global and region distributions, per-base runs, per-window means and
per-window threshold counts. Compressed outputs are bgzf, matching mosdepth.

The distribution emission rule was reverse-engineered from the fixtures and
is the non-obvious part: every depth from 0 up to min(300, max) gets a row
whether or not any base sits at it, above 300 only depths that occur and lie
strictly below the maximum do. So the maximum gets a row when it falls inside
the dense range and none when it does not. The global distribution tops out
at 866 with a maximum of 867, while the region distribution does emit its
maximum of 204.

The region distribution is over windows and their rounded mean depth, not
over bases.

Parity tests drive the library directly and compare every mosdepth output
against the committed fixtures: all eight match, including the 1094-line
global distribution and the 721-interval per-base BED.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
One rayon worker per contig, each holding its own depth array, feeding a
DepthAccum, a BamStatAccum and a PreseqAccum from the same record stream, so
the alignment is read once. A separate pass over unmapped records feeds the
counters flagstat and idxstats report. Workers run longest contig first and
their number is bounded by --max-depth-workers, defaulting to a 4 GB budget
divided by the largest contig, because each worker costs four bytes per base.

Outputs land under mosdepth/, samtools/ and preseq/, or flat with
--flat-output. Input without duplicate marks is rejected unless
--skip-dup-check is passed.

Also fixes the samtools stats header, which hardcoded "rustqc rna" and so
labelled DNA output as RNA output.

End-to-end parity tests run the binary and compare against the fixtures:
all six mosdepth files match byte for byte, flagstat and idxstats match
exactly, and all 1889 data lines of samtools stats match. The stats header
differs by design, RustQC naming itself rather than reproducing samtools'
version banner, so that comparison is on data lines.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
InputSummary gains an optional dna block carrying genome length, covered
bases, mean, median and maximum coverage, the percentage of the reference at
or above each requested threshold, and the duplicate rate. An input carries
either the RNA fields or this one, never both.

Coverage thresholds are a list of objects rather than a map so the requested
order survives serialisation; a map keyed by the threshold would sort "10"
before "5".

CITATIONS.md for a dna run cites mosdepth, samtools and preseq, and none of
the RNA-only tools. The header is now shared between both writers.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
…n used

Closes two gaps left open in this PR.

The bgzf BED outputs now get a .csi index built through htslib's
tbx_index_build, as mosdepth writes and as tabix needs to seek into them. CSI
rather than TBI because CSI carries no 512 Mb coordinate ceiling.

Indexes are not compared byte for byte: an index is binary metadata over the
compressed blocks, and two writers answering the same queries need not produce
the same bytes. The test asserts instead that a region query returns the same
rows through our index as through mosdepth's, going through the tabix binary
because rust-htslib's tabix reader ends a fetched region with a
TabixTruncatedRecord rather than stopping, and does so at different points for
the two files. It skips where tabix is absent.

CITATIONS.md for a dna run now cites samtools v1.24, the version its fixtures
were generated with, instead of the v1.22.1 the rna pipeline was validated
against. Each pipeline cites the version it was actually compared with rather
than both claiming the newer one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Matches Picard 3.4.0 byte for byte on the project fixture, metrics row and
all 170 histogram lines.

Every rule was measured against Picard's own output rather than recalled. The
inclusion filter is paired, not secondary, supplementary, duplicate or
unmapped, mate mapped, and a positive TLEN so each pair counts once. Proper
pair is deliberately not required: requiring it drops one pair and shortens
the maximum from 300 to 239 on this data.

Mean and standard deviation are over the histogram trimmed to DEVIATIONS
median absolute deviations either side of the median, with the n-1
denominator; minimum and maximum are over the untrimmed set. WIDTH_OF_XX
grows a window symmetrically around the median until it covers the
percentile, reporting 2i+1; all eleven widths match.

The fixture does not exercise trimming, since nothing on it lies beyond ten
MADs of the median, so that path has its own unit test.

Fixtures are generated with the JVM locale pinned to English: a French
default writes "3,531312" where an English one writes "3.531312", which would
make them depend on the machine that produced them. Picard's four-line
preamble is stripped, holding only a command line and a timestamp.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Matches Picard 3.4.0 on every column and every one of the 251 histogram
lines, with two exceptions noted below.

The exclusion model was derived by reproducing Picard's own numbers until
each fraction matched, not recalled. Unmapped, secondary and supplementary
records never enter the calculation. Every other record's reference-consuming
bases form the denominator of all PCT_EXC_* columns, 670989 on the fixture.
Exclusions then apply in order: duplicate, low mapping quality and unpaired
remove a whole read; low base quality and mate overlap remove single bases;
depth beyond COVERAGE_CAP is counted as excess. What survives is the high
quality coverage the histogram reports. SD_COVERAGE is the sample standard
deviation over every base of the territory, uncovered ones included.

This needs its own depth accumulator rather than a correction applied to the
mosdepth one, because the two tools do not agree on which reads or which
bases count. That was the design's reason for keeping the accumulators
separate and it holds up.

HET_SNP_SENSITIVITY and HET_SNP_Q come from Picard's TheoreticalSensitivity,
a Monte Carlo simulation whose draws would have to be reproduced bit for bit.
Both are written as "?", the marker Picard itself uses for a value it cannot
compute, and the parity test permits a difference in exactly those two
columns and nowhere else.

CollectWgsMetrics needs --reference to count the reference's non-N bases;
without one it is skipped with a warning rather than reported against a wrong
genome territory.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Matches Picard 3.4.0 byte for byte: the 101-row detail table and the summary,
AT_DROPOUT, GC_DROPOUT and the GC_NC columns included.

An earlier attempt to infer the rules from Picard's output failed, so these
come from its source, GcBiasUtils and GcBiasMetricsCollector. Three of them
would not have been guessed:

Windows slide over positions 1 to len - window_size - 1. Both ends are
clipped, so a 40001 base reference gives 39900 windows of 100 bases rather
than the 39902 a naive reading produces, and the GC value truncates rather
than rounds.

A read is assigned to the window at its alignment start, except on the
reverse strand, where it goes to alignment_end - window_size. That is not the
read's 5' end, and no offset applied to either end reproduces it.

Only unmapped reads and reads with an empty sequence are skipped. Secondary
and supplementary alignments count, which is the difference between 5640 and
5642 read starts here. Unmapped reads still count towards TOTAL_CLUSTERS even
though they reach nothing else.

Two further details came out of the fixture: GC_NC_x_y is a mean weighted by
each bin's window count rather than a plain average over bins, and the GC
tables carry two trailing blank lines where the other Picard tables carry one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
--targets switches the run into targeted mode and produces hs_metrics.txt;
--baits defaults to the same intervals. BED input is parsed and merged, since
overlapping targets would otherwise inflate the territory and double-count
on-target bases.

All 58 computable columns match Picard 3.4.0 exactly, including
HS_LIBRARY_SIZE, which solves the Lander-Waterman equation by bisection the
way Picard's own estimator does.

The reason an earlier attempt missed by 0.8 percent is that HsMetrics does
not filter the way CollectWgsMetrics does. It clips overlapping mates first,
at the read level, and only then applies the base quality floor; WgsMetrics
does the opposite. That is why the two report different PCT_EXC_BASEQ and
PCT_EXC_OVERLAP on the same file. Two further details came from htsjdk:
only the left-most mate is clipped, losing everything from its mate's start
onwards, and htsjdk's MATCH_OR_MISMATCH is the M operator alone, so = and X
lose their whole element rather than a partial one.

Unmapped records reach no contig worker but still count towards TOTAL_READS,
PF_BASES and the cluster count, so they are fed to both accumulators during
the unmapped pass.

Seven columns are not computed: HET_SNP_SENSITIVITY, HET_SNP_Q, the six
HS_PENALTY levels and FOLD_80_BASE_PENALTY all derive from Picard's Monte
Carlo theoretical sensitivity, and AT_DROPOUT and GC_DROPOUT from a
per-target GC binning not implemented here. Each is written the way Picard
writes a value it cannot compute.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Three pages under docs/dna: an overview of what the pipeline runs and writes,
a mosdepth page, and a Picard page covering all four collectors.

They document the things that actually catch people out rather than restating
the flags: that --mapq defaults to 0 here and to 30 for rna, that mate-overlap
correction is often a factor of two rather than a rounding detail, that the
distribution files always emit depths 0 to 300 and never the maximum above
that range, that reverse-strand reads are GC-binned by their far end, and that
CollectHsMetrics and CollectWgsMetrics filter in opposite orders so their
coverage figures are not comparable to each other.

Each page also states plainly which columns are not reproduced and why.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Writes genome_results.txt, ten of the raw data tables and an HTML summary.
genome_results.txt matches Qualimap 2.3 on every line but four, and the
clipping profile, nucleotide content and mapping quality histogram match byte
for byte.

Several of Qualimap's rules are surprising and none were guessable from its
output alone. The reference is split into ceil(len / ceil(len / 400)) windows,
so 397 rather than 400. Coverage counts every primary mapped record with no
filtering at all, counts deletions, and does not correct mate overlaps, which
is why it reports 16.77 where mosdepth reports 6.20. The global mean mapping
quality is the mean of the per-window means with empty windows contributing
zero, hence 2.4178 rather than about 60, while the per-position histogram
truncates that mean instead of rounding it. Mismatches are NM less inserted
bases only. Base composition is counted in reference orientation while the
clipped span selecting which positions count is taken in sequencing
orientation; mixing the two is what Qualimap does and matching it is the only
way the composition agrees.

Four residuals are documented rather than papered over. The mean mapping
quality and the coverage standard deviation differ in the fourth decimal
because Qualimap accumulates them per window. About five reference positions
of 40001 sit one deeper here, which carries into the coverage histogram and
the fractions derived from it. The homopolymer indel classification differs
outright: Qualimap reads a reference context this does not reconstruct, and
reports two polyC indels that no read-derived rule produces, since the deleted
bases are not in the read.

Qualimap's GC content distribution and duplication rate histogram are not
written. The first is computed over a 679-read subsample whose selection rule
is undocumented, the second uses a definition that is not a read-start count.
Emitting tables under those names with different numbers would be worse than
leaving them out.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
rustqc protein sequence reads protein FASTA and reports length statistics,
amino acid composition and defects. The statistics table reproduces
seqkit 2.13.0's `stats -a -T` byte for byte on both fixtures.

Two of seqkit's conventions had to be recovered from its behaviour, and
neither is what a statistics library gives by default. Its quartiles are
Tukey's halves, so Q1 is the median of the lower half rather than an
interpolated value: on the yeast fixture that is 157 where linear
interpolation gives 165. And those halves round half-to-even, so a median of
235.5 is reported as 236 while 376.5 and 516.5 are reported as 376 and 516.
Ordinary rounding gets the first right and the other two wrong.

Beyond seqkit, the report carries per-residue composition and the defects that
make a proteome unusable downstream: stop codons anywhere but the final
position, residues that are not amino acids, byte-identical duplicate
sequences and reused identifiers. Ambiguity codes are counted rather than
flagged, and selenocysteine and pyrrolysine are treated as standard.

The subcommand takes an explicit mode rather than inferring one from which
flags were given, because the three planned modes take entirely different
inputs. Only `sequence` exists so far.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
seqkit walks the distinct lengths from longest down and reports how many it
consumed. Three sequences of lengths 10, 10 and 3 give 1, not 2, because the
two tens are one length.

Both project fixtures happen to have every length distinct, which makes the
two definitions agree and hid this entirely. The discriminating case now has
its own test.

Found while extending the same statistics to FASTQ, where thousands of reads
share a length and the wrong definition reported 3945 against seqkit's 1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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