feat: add support for connections in complexity calculation (@freshjsw)

packages/plugins/cost-limit/src/index.ts

@@ -61,6 +61,7 @@ class CostLimitVisitor {
 
   onOperationDefinitionEnter(operation: OperationDefinitionNode): void {
     const complexity = this.computeComplexity(operation);
+
     if (complexity > this.config.maxCost) {
       const message = this.config.exposeLimits
         ? `Query Cost limit of ${this.config.maxCost} exceeded, found ${complexity}.`
@@ -101,6 +102,19 @@ class CostLimitVisitor {
     let cost = this.config.scalarCost;
     if ('selectionSet' in node && node.selectionSet) {
       cost = this.config.objectCost;
+
+      let setMultiplier = 1;
+      if ('arguments' in node && node.arguments) {
+        for (const arg of node.arguments) {
+          if (arg.name.value === 'first' || arg.name.value === 'last') {
+            if (arg.value.kind === 'IntValue') {
+              setMultiplier = Math.max(parseInt(arg.value.value, 10) ?? 1, setMultiplier);
+            }
+            break;
+          }
+        }
+      }
+
       for (const child of node.selectionSet.selections) {
         if (
           this.config.flattenFragments &&
@@ -111,6 +125,8 @@ class CostLimitVisitor {
           cost += this.config.depthCostFactor * this.computeComplexity(child, depth + 1);
         }
       }
+      // Apply setMultiplier to the total cost of current node and its children
+      cost *= setMultiplier;
     } else if (node.kind === Kind.FRAGMENT_SPREAD) {
       if (this.visitedFragments.has(node.name.value)) {
         const visitCost = this.visitedFragments.get(node.name.value) ?? 0;

packages/plugins/cost-limit/test/index.spec.ts

@@ -17,7 +17,7 @@ const typeDefinitions = `
   }
 
   type Query {
-    books: [Book]
+    books(first: Int, last: Int): [Book]
     getBook(title: String): Book
   }
 `;
@@ -35,7 +35,15 @@ const books = [
 
 const resolvers = {
   Query: {
-    books: () => books,
+    books: (_: any, { first, last }: { first?: number; last?: number }) => {
+      if (first !== undefined) {
+        return books.slice(0, first);
+      }
+      if (last !== undefined) {
+        return books.slice(-last);
+      }
+      return books;
+    },
     getBook: (_: any, { title }: { title: string }) => books.find((book) => book.title === title),
   },
 };
@@ -353,4 +361,74 @@ describe('costLimitPlugin', () => {
       `Syntax Error: Query Cost limit of ${maxCost} exceeded, found 12.`,
     ]);
   });
+
+  it('supports pagination using first or last', async () => {
+    const maxCost = 20;
+    const testkit = createTestkit(
+      [
+        costLimitPlugin({
+          maxCost: maxCost,
+          objectCost: 4,
+          scalarCost: 2,
+          depthCostFactor: 1.5,
+          ignoreIntrospection: true,
+        }),
+      ],
+      schema,
+    );
+    const result = await testkit.execute(`
+    query {
+      firstBooks: books(first: 1) {
+        title
+        author
+      }
+
+      lastBooks: books(last: 1) {
+        title
+        author
+      }
+    }
+    `);
+
+    assertSingleExecutionValue(result);
+    expect(result.errors).toBeUndefined();
+  });
+
+  it('rejects pagination using first or last when cost limit is exceeded', async () => {
+    const maxCost = 57;
+    const testkit = createTestkit(
+      [
+        costLimitPlugin({
+          maxCost: maxCost,
+          objectCost: 4,
+          scalarCost: 2,
+          depthCostFactor: 1.5,
+          ignoreIntrospection: true,
+        }),
+      ],
+      schema,
+    );
+    const result = await testkit.execute(`
+    query {
+      firstBooks: books(first: 2) {
+        title
+        author
+      }
+      ...BookFragmentLast3
+
+      fragment BookFragmentLast3 on Query {
+        books(last: 3) {
+          title
+          author
+        }
+      }
+    }
+    `);
+
+    assertSingleExecutionValue(result);
+    expect(result.errors).toBeDefined();
+    expect(result.errors?.map((error) => error.message)).toEqual([
+      `Syntax Error: Query Cost limit of ${maxCost} exceeded, found 77.`,
+    ]);
+  });
 });