refactor: undefined to null

Replace undefined with null as return value for splitPackageReference since this is an intentionally missing value.

Author: ComradeVanti

src/cli/cmd-deps.ts

@@ -97,17 +97,13 @@ openupm deps @`
 
         const [packageName, requestedVersion] = splitPackageReference(pkg);
 
-        if (
-          requestedVersion !== undefined &&
-          isZod(requestedVersion, PackageUrl)
-        ) {
+        if (requestedVersion !== null && isZod(requestedVersion, PackageUrl)) {
           log.error("", "cannot get dependencies for url-version");
           return process.exit(ResultCodes.Error);
         }
 
         const latestVersion =
-          requestedVersion !== undefined &&
-          isZod(requestedVersion, SemanticVersion)
+          requestedVersion !== null && isZod(requestedVersion, SemanticVersion)
             ? requestedVersion
             : (
                 await queryAllRegistriesLazy(sources, (source) =>

src/domain/package-reference.ts

@@ -60,12 +60,12 @@ export function isPackageReference(s: string): s is PackageReference {
  */
 export function splitPackageReference(
   reference: PackageReference
-): [DomainName, VersionReference | undefined] {
+): [DomainName, VersionReference | null] {
   const [name, version] = trySplitAtFirstOccurrenceOf(reference, "@") as [
     DomainName,
     VersionReference | null
   ];
-  return [name, version ?? undefined];
+  return [name, version];
 }
 
 /**

test/unit/domain/package-reference.test.ts

@@ -83,7 +83,7 @@ describe("package-reference", () => {
         makePackageReference(name, version)
       );
       expect(actualName).toEqual(name);
-      expect(actualVersion).toEqual(version);
+      expect(actualVersion).toEqual(version ?? null);
     }
 
     it("should split package without version", () =>