refactor: undefined to null

Replace undefined with null as the return value for  tryGetLatestVersion since the null here represents an intentionally missing value. Also convert it to a named function to be more in line with other functions.

src/cli/output-formatting.ts

@@ -39,7 +39,7 @@ export function formatAsTable(
     if (packument.date) {
       date = packument.date.toISOString().slice(0, 10);
     }
-    assert(version !== undefined);
+    assert(version !== null);
     return [name, version, date];
   }
 
@@ -65,7 +65,7 @@ export function formatPackumentInfo(
 
   const versionCount = recordKeys(packument.versions).length;
   const ver = tryGetLatestVersion(packument);
-  assert(ver !== undefined);
+  assert(ver !== null);
   const verInfo = packument.versions[ver]!;
   const license = verInfo.license || "proprietary or unlicensed";
   const displayName = verInfo.displayName;

src/domain/packument.ts

@@ -90,15 +90,15 @@ const hasLatestDistTag = <T extends VersionedPackument>(
  * @param packument The package. All properties are assumed to be potentially
  * missing.
  */
-export const tryGetLatestVersion = function (
+export function tryGetLatestVersion(
   packument: VersionedPackument
-): SemanticVersion | undefined {
+): SemanticVersion | null {
   if (hasLatestDistTag(packument)) return packument["dist-tags"].latest;
 
   if (packument.version !== undefined) return packument.version;
 
-  return undefined;
-};
+  return null;
+}
 
 /**
  * Attempts to get a specific version from a packument.
@@ -193,7 +193,7 @@ export function tryResolvePackumentVersion(
   // Find the latest version
   if (requestedVersion === undefined || requestedVersion === "latest") {
     let latestVersion = tryGetLatestVersion(packument);
-    if (latestVersion === undefined) latestVersion = availableVersions.at(-1)!;
+    if (latestVersion === null) latestVersion = availableVersions.at(-1)!;
     return Ok(tryGetPackumentVersion(packument, latestVersion)!);
   }
 

test/unit/domain/packument.test.ts

@@ -38,7 +38,7 @@ describe("packument", () => {
 
       const version = tryGetLatestVersion(packument);
 
-      expect(version).toBeUndefined();
+      expect(version).toBeNull();
     });
   });