Sorter: Extract validation out of scoring

.changeset/sweet-trainers-drop.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": minor
+---
+
+Split out validation function for the `sorter` widget. This can be used to check if the user has made any changes to the sorting order, confirming whether or not the question can be scored.

packages/perseus/src/widgets/sorter/score-sorter.test.ts

@@ -29,16 +29,4 @@ describe("scoreSorter", () => {
         const result = scoreSorter(userInput, rubric);
         expect(result).toHaveBeenAnsweredIncorrectly();
     });
-
-    it("is invalid when the user has not made any changes", () => {
-        const userInput: PerseusSorterUserInput = {
-            options: ["$15$ grams", "$55$ grams", "$0.005$ kilograms"],
-            changed: false,
-        };
-        const rubric: PerseusSorterRubric = {
-            correct: ["$0.005$ kilograms", "$15$ grams", "$55$ grams"],
-        };
-        const result = scoreSorter(userInput, rubric);
-        expect(result).toHaveInvalidInput();
-    });
 });

packages/perseus/src/widgets/sorter/score-sorter.ts

@@ -1,5 +1,7 @@
 import Util from "../../util";
 
+import validateSorter from "./validate-sorter";
+
 import type {PerseusScore} from "../../types";
 import type {
     PerseusSorterRubric,
@@ -10,17 +12,9 @@ function scoreSorter(
     userInput: PerseusSorterUserInput,
     rubric: PerseusSorterRubric,
 ): PerseusScore {
-    // If the sorter widget hasn't been changed yet, we treat it as "empty" which
-    // prevents the "Check" button from becoming active. We want the user
-    // to make a change before trying to move forward. This makes an
-    // assumption that the initial order isn't the correct order! However,
-    // this should be rare if it happens, and interacting with the list
-    // will enable the button, so they won't be locked out of progressing.
-    if (!userInput.changed) {
-        return {
-            type: "invalid",
-            message: null,
-        };
+    const validationError = validateSorter(userInput, rubric);
+    if (validationError) {
+        return validationError;
     }
 
     const correct = Util.deepEq(userInput.options, rubric.correct);

packages/perseus/src/widgets/sorter/validate-sorter.test.ts

@@ -0,0 +1,32 @@
+import validateSorter from "./validate-sorter";
+
+import type {
+    PerseusSorterRubric,
+    PerseusSorterUserInput,
+} from "../../validation.types";
+
+describe("validateSorter", () => {
+    it("is invalid when the user has not made any changes", () => {
+        const userInput: PerseusSorterUserInput = {
+            options: ["$15$ grams", "$55$ grams", "$0.005$ kilograms"],
+            changed: false,
+        };
+        const rubric: PerseusSorterRubric = {
+            correct: ["$0.005$ kilograms", "$15$ grams", "$55$ grams"],
+        };
+        const result = validateSorter(userInput, rubric);
+        expect(result).toHaveInvalidInput();
+    });
+
+    it("returns null when the user has made any changes", () => {
+        const userInput: PerseusSorterUserInput = {
+            options: ["$55$ grams", "$0.005$ kilograms", "$15$ grams"],
+            changed: true,
+        };
+        const rubric: PerseusSorterRubric = {
+            correct: ["$0.005$ kilograms", "$15$ grams", "$55$ grams"],
+        };
+        const result = validateSorter(userInput, rubric);
+        expect(result).toBeNull();
+    });
+});

packages/perseus/src/widgets/sorter/validate-sorter.ts

@@ -0,0 +1,26 @@
+import type {PerseusScore} from "../../types";
+import type {
+    PerseusSorterRubric,
+    PerseusSorterUserInput,
+} from "../../validation.types";
+
+function validateSorter(
+    userInput: PerseusSorterUserInput,
+    rubric: PerseusSorterRubric,
+): Extract<PerseusScore, {type: "invalid"}> | null {
+    // If the sorter widget hasn't been changed yet, we treat it as "empty" which
+    // prevents the "Check" button from becoming active. We want the user
+    // to make a change before trying to move forward. This makes an
+    // assumption that the initial order isn't the correct order! However,
+    // this should be rare if it happens, and interacting with the list
+    // will enable the button, so they won't be locked out of progressing.
+    if (!userInput.changed) {
+        return {
+            type: "invalid",
+            message: null,
+        };
+    }
+    return null;
+}
+
+export default validateSorter;