Merge pull request #859 from guardian/aa/lint-flatmap

Add linting rule to prefer `.flatMap(...)` over `.map(...).flat()`

package.json

@@ -25,6 +25,7 @@
     "esbuild-jest": "^0.5.0",
     "eslint": "^8.57.0",
     "eslint-plugin-prettier": "^5.1.3",
+    "eslint-plugin-unicorn": "^51.0.1",
     "jest": "^29.7.0",
     "npm-run-all": "^4.1.5",
     "tsx": "^4.7.1",
@@ -33,11 +34,13 @@
   "eslintConfig": {
     "extends": "@guardian/eslint-config-typescript",
     "plugins": [
-      "prettier"
+      "prettier",
+      "unicorn"
     ],
     "rules": {
       "prettier/prettier": "error",
-      "@typescript-eslint/no-non-null-assertion": "error"
+      "@typescript-eslint/no-non-null-assertion": "error",
+      "unicorn/prefer-array-flat-map": "error"
     }
   },
   "eslintIgnore": [

packages/repocop/src/evaluation/repository.ts

@@ -320,8 +320,7 @@ export function collectAndFormatUrgentSnykAlerts(
 		.map((project) => project.id);
 
 	const snykIssuesForRepo: SnykIssue[] = snykProjectIdsForRepo
-		.map((projectId) => getIssuesForProject(projectId, snykIssues))
-		.flat()
+		.flatMap((projectId) => getIssuesForProject(projectId, snykIssues))
 		.filter((i) => !i.attributes.ignored);
 
 	const processedVulns = snykIssuesForRepo.map((v) =>
@@ -470,8 +469,7 @@ export function snykAlertToRepocopVulnerability(
 	projects: SnykProject[],
 ): RepocopVulnerability {
 	const packages = (issue.attributes.coordinates ?? [])
-		.map((c) => c.representations)
-		.flat()
+		.flatMap((c) => c.representations)
 		.filter((r) => r !== null) as Dependency[];
 
 	const projectIdFromIssue = issue.relationships.scan_item.data.id;

packages/repocop/src/index.ts

@@ -82,7 +82,7 @@ export async function main() {
 	const repocopRules = evaluationResults.map((r) => r.repocopRules);
 	const severityPredicate = (x: RepocopVulnerability) => x.severity === 'high';
 	const [high, critical] = partition(
-		evaluationResults.map((r) => r.vulnerabilities).flat(),
+		evaluationResults.flatMap((r) => r.vulnerabilities),
 		severityPredicate,
 	);
 

packages/repocop/src/remediation/vuln-digest/vuln-digest.ts

@@ -56,7 +56,7 @@ export function createDigest(
 	results: EvaluationResult[],
 ): VulnerabilityDigest | undefined {
 	const resultsForTeam = getOwningRepos(team, repoOwners, results);
-	const vulns = resultsForTeam.map((r) => r.vulnerabilities).flat();
+	const vulns = resultsForTeam.flatMap((r) => r.vulnerabilities);
 
 	const totalVulnsCount = vulns.length;