fix(client): provide return types for get-completion-percentage (#49458)

fix: provide return types

I also moved the undefined check closer to the source, so it's clearer
what is missing

client/src/templates/Challenges/redux/selectors.js

@@ -94,30 +94,25 @@ export const challengeDataSelector = state => {
 export const currentBlockIdsSelector = state => {
   const { block, certification, challengeType } = challengeMetaSelector(state);
   const allChallengesInfo = allChallengesInfoSelector(state);
-  const currentBlockIds = getCurrentBlockIds(
+
+  return getCurrentBlockIds(
     allChallengesInfo,
     block,
     certification,
     challengeType
   );
-
-  if (!currentBlockIds) {
-    return [];
-  }
-
-  return currentBlockIds;
 };
 
 export const completedChallengesInBlockSelector = state => {
   const completedChallengesIds = completedChallengesIdsSelector(state);
   const currentBlockIds = currentBlockIdsSelector(state);
   const { id } = challengeMetaSelector(state);
-  const completedChallengesInBlock = getCompletedChallengesInBlock(
+
+  return getCompletedChallengesInBlock(
     completedChallengesIds,
     currentBlockIds,
     id
   );
-  return completedChallengesInBlock;
 };
 
 export const completedPercentageSelector = state => {

client/src/utils/get-completion-percentage.ts

@@ -23,7 +23,7 @@ export function getCompletedChallengesInBlock(
   completedChallengesIds: string[],
   currentBlockIds: string[],
   currentChallengeId: string
-) {
+): number {
   const oldCompletionCount = completedChallengesIds.filter(challengeId =>
     currentBlockIds.includes(challengeId)
   ).length;
@@ -39,13 +39,14 @@ export const getCurrentBlockIds = (
   block: string,
   certification: string,
   challengeType: number
-) => {
+): string[] => {
   const { challengeEdges, certificateNodes } = allChallengesInfo;
-  const currentCertificateIds = certificateNodes
-    .filter(
-      node => dasherize(node.challenge.certification) === certification
-    )[0]
-    ?.challenge.tests.map(test => test.id);
+  const currentCertificateIds =
+    certificateNodes
+      .filter(
+        node => dasherize(node.challenge.certification) === certification
+      )[0]
+      ?.challenge.tests.map(test => test.id) ?? [];
   const currentBlockIds = challengeEdges
     .filter(edge => edge.node.challenge.block === block)
     .map(edge => edge.node.challenge.id);