Stop warning that a breakend has no END/SVLEN (#497)

eidolon/src/gen_reads/utils/runner.rs

@@ -3678,8 +3678,8 @@ fn alt_haplotype_window(
 /// Builds a sorted, contiguous list of `(start, end, multiplier)` coverage
 /// segments spanning `[0, block_end)`. Default multiplier is `1.0`; each
 /// symbolic SV multiplies the multiplier in its span (overlapping SVs compose
-/// multiplicatively). SVs without a usable span (no END / SVLEN) or with a
-/// multiplier of `1.0` are skipped silently.
+/// multiplicatively). Breakends and SVs with a multiplier of `1.0` are skipped; an
+/// SV without a usable span (no END / SVLEN) is skipped with a warning.
 fn build_coverage_multipliers(
     sv_variants: &[Variant],
     ploidy: usize,
@@ -3699,6 +3699,13 @@ fn build_coverage_multipliers(
         // Convert the 0-based-stored location back to the VCF's 1-based POS
         // so SvData::span() (which expects 1-based) returns the right count.
         let pos_1based = v.location.saturating_add(1);
+        if sv.sv_type == SvType::Bnd {
+            // A breakend is a point (VCF 4.2 §5.4) with no copy-number change, so it has
+            // no span to modulate. Missing END/SVLEN is expected here, not a defect in the
+            // input, and the warning below is for SVs that should have one (#497).
+            debug!("Breakend at 1-based POS {pos_1based}: a point event, no coverage modulation");
+            continue;
+        }
         let span_bases = match sv.span(pos_1based) {
             Some(n) if n > 0 => n,
             _ => {

eidolon/tests/bnd_no_span_warning.rs

@@ -0,0 +1,87 @@
+//! A well-formed breakend has no END or SVLEN (VCF 4.2 §5.4: it is a point), so the
+//! coverage pass must not warn that one is missing. A symbolic SV that does need a span and
+//! lacks it must still warn (#497).
+//!
+//! The breakend case asserts the DEBUG line as well as the missing WARN: without it, a
+//! breakend that never reached the coverage pass would pass the test for the wrong reason.
+//! Both tests read the written log: the terminal logger sends WARN to stdout, not stderr.
+
+mod common;
+use common::{GenReadsConfig, eidolon, fresh_workdir, h1n1_reference};
+use std::io::Write as _;
+
+const MISSING_SPAN_WARN: &str = "has no END/SVLEN";
+const BND_DEBUG: &str = "Breakend at 1-based POS 600: a point event";
+
+fn write_vcf(path: &std::path::Path, records: &[&str]) {
+    let mut f = std::fs::File::create(path).unwrap();
+    writeln!(f, "##fileformat=VCFv4.2").unwrap();
+    writeln!(
+        f,
+        "##FORMAT=<ID=GT,Number=1,Type=String,Description=\"Genotype\">"
+    )
+    .unwrap();
+    writeln!(
+        f,
+        "#CHROM\tPOS\tID\tREF\tALT\tQUAL\tFILTER\tINFO\tFORMAT\tS"
+    )
+    .unwrap();
+    for r in records {
+        writeln!(f, "{r}").unwrap();
+    }
+}
+
+/// Runs gen-reads on `records` at debug log level and returns the written log.
+fn run(records: &[&str]) -> String {
+    let (_dir, work) = fresh_workdir();
+    let vcf = work.join("in.vcf");
+    write_vcf(&vcf, records);
+    let mut config = GenReadsConfig::new(h1n1_reference(), work.clone(), "run");
+    config.coverage = 5;
+    config.produce_fastq = true;
+    config.input_vcf = Some(vcf);
+    config.sv_rate_scale = Some(0.0); // only the supplied records, no de novo SVs
+    let yaml = config.write_yaml();
+    let log = work.join("run.log");
+    let out = eidolon()
+        .args(["--log-level", "debug", "--log-dest"])
+        .arg(&log)
+        .args(["gen-reads", "-c"])
+        .arg(yaml.path())
+        .output()
+        .unwrap();
+    assert!(
+        out.status.success(),
+        "gen-reads failed: {}",
+        String::from_utf8_lossy(&out.stderr)
+    );
+    std::fs::read_to_string(&log).unwrap()
+}
+
+#[test]
+fn a_breakend_without_end_or_svlen_does_not_warn() {
+    // REF bases are the actual reference at those positions.
+    let log = run(&[
+        "H1N1_HA\t600\t.\tT\tT[H1N1_PB2:900[\t60\tPASS\tSVTYPE=BND\tGT\t1/1",
+        "H1N1_PB2\t900\t.\tG\t]H1N1_HA:600]G\t60\tPASS\tSVTYPE=BND\tGT\t1/1",
+    ]);
+    assert!(
+        log.contains(BND_DEBUG),
+        "the breakend must reach the coverage pass and be skipped there:\n{log}"
+    );
+    assert!(
+        !log.contains(MISSING_SPAN_WARN),
+        "a breakend is not missing a span:\n{log}"
+    );
+}
+
+#[test]
+fn a_deletion_without_end_or_svlen_still_warns() {
+    let log = run(&["H1N1_HA\t600\t.\tT\t<DEL>\t60\tPASS\tSVTYPE=DEL\tGT\t1/1"]);
+    assert!(
+        log.contains(&format!(
+            "Symbolic SV at 1-based POS 600 {MISSING_SPAN_WARN}"
+        )),
+        "a <DEL> with no span is under-specified and must say so:\n{log}"
+    );
+}