Prefer License-Expression with --from=mixed

piplicenses.py

@@ -625,21 +625,18 @@ def select_license_by_source(
     license_meta: str,
     license_expression: str,
 ) -> set[str]:
+    if license_expression != LICENSE_UNKNOWN:
+        return {license_expression}
+
     license_classifier_set = set(license_classifier) or {LICENSE_UNKNOWN}
     if (
         from_source == FromArg.CLASSIFIER
         or from_source == FromArg.MIXED
         and len(license_classifier) > 0
     ):
         return license_classifier_set
-    elif (
-        from_source == FromArg.META
-        or from_source == FromArg.MIXED
-        and license_meta != LICENSE_UNKNOWN
-    ):
-        return {license_meta}
     else:
-        return {license_expression}
+        return {license_meta}
 
 
 def get_output_fields(args: CustomNamespace) -> list[str]:

test_piplicenses.py

@@ -334,6 +334,15 @@ def test_select_license_by_source(self) -> None:
                 FromArg.MIXED, [], LICENSE_UNKNOWN, "MIT"
             ),
         )
+        self.assertEqual(
+            {"Apache-2.0"},
+            select_license_by_source(
+                FromArg.MIXED,
+                ["Apache License 2.0"],
+                "Apache",
+                "Apache-2.0",
+            ),
+        )
         self.assertEqual(
             {"Apache-2.0"},
             select_license_by_source(