System version doesn't need to match when assigning a code

A code assigned with a system may include a version as part of the
system. This is generally intended to refer to the system's published
version in the world, and is not guaranteed to match the version of the
CodeSystem FHIR resource. Fish for any version when resolving the
system, and do not emit a warning even if the versions don't match.

src/fhirtypes/common.ts

@@ -942,9 +942,12 @@ export function replaceReferences<T extends AssignmentRule | CaretValueRule>(
       }
     }
   } else if (value instanceof FshCode) {
+    // the version on a CodeSystem resource is not the same as the system's actual version out in the world.
+    // so, they don't need to match.
+    const baseSystem = value.system?.split('|')[0];
     const codeSystemMeta = fishForMetadataBestVersion(
       fisher,
-      value.system,
+      baseSystem,
       rule.sourceInfo,
       Type.CodeSystem
     );

test/export/InstanceExporter.test.ts

@@ -6287,6 +6287,36 @@ describe('InstanceExporter', () => {
       ]);
     });
 
+    it('should assign a code with a version while replacing the code system name with its url regardless of the specified version', () => {
+      // the version on a CodeSystem resource is not the same as the system's actual version out in the world.
+      // so, they don't need to match.
+      const brightInstance = new Instance('BrightObservation');
+      brightInstance.instanceOf = 'Observation';
+      const assignedCodeRule = new AssignmentRule('code');
+      assignedCodeRule.value = new FshCode('bright', 'Visible|1.2.3');
+      brightInstance.rules.push(assignedCodeRule);
+      doc.instances.set(brightInstance.name, brightInstance);
+
+      const visibleSystem = new FshCodeSystem('Visible');
+      const visibleSystemUrl = new CaretValueRule('');
+      visibleSystemUrl.caretPath = 'url';
+      visibleSystemUrl.value = 'http://hl7.org/fhir/us/minimal/CodeSystem/Visible';
+      const visibleSystemVersion = new CaretValueRule('');
+      visibleSystemVersion.caretPath = 'version';
+      visibleSystemVersion.value = '1.0.0';
+      visibleSystem.rules.push(visibleSystemUrl, visibleSystemVersion);
+      doc.codeSystems.set(visibleSystem.name, visibleSystem);
+      const exported = exportInstance(brightInstance);
+      expect(exported.code.coding).toEqual([
+        {
+          code: 'bright',
+          version: '1.2.3',
+          system: 'http://hl7.org/fhir/us/minimal/CodeSystem/Visible'
+        }
+      ]);
+      expect(loggerSpy.getAllMessages('warn')).toHaveLength(0);
+    });
+
     it('should assign a code to a top level element if the code system was defined as an instance of usage definition', () => {
       const visibleSystem = new Instance('Visible');
       visibleSystem.instanceOf = 'CodeSystem';