Update and Add Tests for Merging Versions

Author: srilman

conda_lock/src_parser/__init__.py

@@ -537,29 +537,43 @@ def aggregate_lock_specs(
         [lock_spec.dependencies for lock_spec in lock_specs]
     ):
         key = (dep.manager, dep.name)
+        new_dep = dep.copy()
         if key in unique_deps:
             prev_dep = unique_deps[key]
 
             # Override existing, but merge selectors
             previous_selectors = prev_dep.selectors
             previous_selectors |= dep.selectors
-            dep.selectors = previous_selectors
+            new_dep.selectors = previous_selectors
 
-            # If bold old and new are VersionedDependency, combine versions
+            # If bold old and new are VersionedDependency, combine version strings together
+            # If there are conflicting versions, they will be handled by the solver
             if isinstance(prev_dep, VersionedDependency) and isinstance(
                 dep, VersionedDependency
             ):
+                assert isinstance(new_dep, VersionedDependency)
+
+                # MatchSpecs are expressions in DNF form: `|` is OR and `,` is AND
                 prev_versions = [
-                    set(sec.split(",")) for sec in prev_dep.version.split("|")
+                    set(sec.split(","))
+                    for sec in prev_dep.version.split("|")
+                    if sec != ""
+                ]
+                new_versions = [
+                    set(sec.split(",")) for sec in dep.version.split("|") if sec != ""
                 ]
-                new_versions = [set(sec.split(",")) for sec in dep.version.split("|")]
+                # To AND two DNF expressions, we essentially perform the distributive law
+                # ORing every pair of terms in the individual expressions
+                # Ex: (AB | CD) (AC | BD) = ABAC | ABBD | CDAC | CDBC = ABC | ABD | ACD | BCD
                 cross_versions = [
                     prev | new for prev, new in product(prev_versions, new_versions)
                 ]
-                final_versions = set(",".join(subset) for subset in cross_versions)
-                dep.version = "|".join(final_versions)
+                final_versions = set(
+                    ",".join(sorted(subset, reverse=True)) for subset in cross_versions
+                )
+                new_dep.version = "|".join(sorted(final_versions, reverse=True))
 
-        unique_deps[key] = dep
+        unique_deps[key] = new_dep
 
     dependencies = list(unique_deps.values())
     try:

tests/test_conda_lock.py

@@ -1123,7 +1123,7 @@ def test_aggregate_lock_specs_multiple_platforms():
     assert actual.content_hash() == expected.content_hash()
 
 
-def test_aggregate_lock_specs_override_version():
+def test_aggregate_lock_specs_combine_version():
     base_spec = LockSpecification(
         dependencies=[_make_spec("package", "=1.0")],
         channels=[Channel.from_string("conda-forge")],
@@ -1139,8 +1139,28 @@ def test_aggregate_lock_specs_override_version():
     )
 
     agg_spec = aggregate_lock_specs([base_spec, override_spec])
+    assert agg_spec.dependencies == [_make_spec("package", "=2.0,=1.0")]
 
-    assert agg_spec.dependencies == override_spec.dependencies
+
+def test_aggregate_lock_specs_with_union_version():
+    base_spec = LockSpecification(
+        dependencies=[_make_spec("package", "=1.0|>2")],
+        channels=[Channel.from_string("conda-forge")],
+        platforms=["linux-64"],
+        sources=[Path("base.yml")],
+    )
+
+    override_spec = LockSpecification(
+        dependencies=[_make_spec("package", "=2.0,<3.0.0")],
+        channels=[Channel.from_string("internal"), Channel.from_string("conda-forge")],
+        platforms=["linux-64"],
+        sources=[Path("override.yml")],
+    )
+
+    agg_spec = aggregate_lock_specs([base_spec, override_spec])
+    assert agg_spec.dependencies == [
+        _make_spec("package", ">2,=2.0,<3.0.0|=2.0,=1.0,<3.0.0")
+    ]
 
 
 def test_aggregate_lock_specs_invalid_channels():