MRG: Fix manifest nhashes (#575)

* use n_hashes sig fn for accurate manifest n_hashes

* use sigstrait isntead

* back to v3 for lockfile

src/python/tests/test_sketch.py

@@ -573,10 +573,10 @@ def test_zip_manifest(runtmp, capfd):
     assert len(manifest) == len(rows)
     assert len(manifest) == 3
 
-    md5_list = [row["md5"] for row in manifest.rows]
-    assert "9191284a3a23a913d8d410f3d53ce8f0" in md5_list
-    assert "d663bb55b2a0f8782c53c8af89f20fff" in md5_list
-    assert "bf752903d635b1eb83c53fe4aae951db" in md5_list
+    md5_nhashes = [(row["md5"], row["n_hashes"]) for row in manifest.rows]
+    assert ("9191284a3a23a913d8d410f3d53ce8f0", 970) in md5_nhashes
+    assert ("d663bb55b2a0f8782c53c8af89f20fff", 925) in md5_nhashes
+    assert ("bf752903d635b1eb83c53fe4aae951db", 955) in md5_nhashes
 
     for sig in siglist:
         assert sig in manifest

src/utils/buildutils.rs

@@ -12,6 +12,7 @@ use sourmash::errors::SourmashError;
 use sourmash::manifest::Record;
 use sourmash::selection::Selection;
 use sourmash::signature::Signature;
+use sourmash::signature::SigsTrait;
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::fmt::Display;
@@ -888,7 +889,7 @@ impl BuildCollection {
                 record.set_filename(Some(filename.clone()));
                 record.set_md5(Some(sig.md5sum()));
                 record.set_md5short(Some(sig.md5sum()[0..8].into()));
-                record.set_n_hashes(Some(sig.size()));
+                record.set_n_hashes(Some(sig.minhash().map(|mh| mh.size()).unwrap_or(0)));
 
                 // note, this needs to be set when writing sigs (not here)
                 // record.set_internal_location("")