chore: Improve tests and typing & package d.ts files.

.c8rc.json

@@ -1,6 +1,6 @@
 {
-  "statements": "78",
-  "branches": "78",
-  "functions": "82",
-  "lines": "78"
+  "statements": "80",
+  "branches": "84",
+  "functions": "88",
+  "lines": "80"
 }

lib/allowlist.ts

@@ -1,5 +1,5 @@
 import type { GitHubAdvisoryId } from "audit-types";
-import { isGitHubAdvisoryId } from "./common";
+import { deduplicate, isGitHubAdvisoryId } from "./common";
 import type { AuditCiPreprocessedConfig } from "./config";
 
 class Allowlist {
@@ -37,12 +37,8 @@ class Allowlist {
     config: Pick<AuditCiPreprocessedConfig, "allowlist">
   ) {
     const { allowlist } = config;
-    // It's possible someone duplicated the inputs.
-    // The solution is to merge into one array, change to set, and back to array.
-    // This will remove duplicates.
-    const set = new Set(allowlist || []);
-    const input = [...set];
-    const allowlistObject = new Allowlist(input);
+    const deduplicatedAllowlist = deduplicate(allowlist || []);
+    const allowlistObject = new Allowlist(deduplicatedAllowlist);
     return allowlistObject;
   }
 }

lib/audit.ts

@@ -15,7 +15,9 @@ const PARTIAL_RETRY_ERROR_MSG = {
   yarn: "503 Service Unavailable",
 };
 
-function getAuditor(packageManager: "npm" | "yarn" | "pnpm") {
+function getAuditor(
+  packageManager: "npm" | "yarn" | "pnpm"
+): typeof yarnAuditer | typeof npmAuditer | typeof pnpmAuditer {
   switch (packageManager) {
     case "yarn":
       return yarnAuditer;

lib/common.ts

@@ -186,8 +186,8 @@ export function matchString(template: string, string_: string) {
     : template === string_;
 }
 
-export function isGitHubAdvisoryId(id: string): id is GitHubAdvisoryId {
-  return id.startsWith("GHSA");
+export function isGitHubAdvisoryId(id: unknown): id is GitHubAdvisoryId {
+  return typeof id === "string" && id.startsWith("GHSA");
 }
 
 export function gitHubAdvisoryUrlToAdvisoryId(url: string): GitHubAdvisoryId {
@@ -199,3 +199,7 @@ export function gitHubAdvisoryIdToUrl<T extends string>(
 ): `https://github.com/advisories/${T}` {
   return `https://github.com/advisories/${id}`;
 }
+
+export function deduplicate(array: readonly string[]) {
+  return [...new Set(array)];
+}