Add support default values for query variables, fixes #50 (#52)

Author: ivome

src/QueryComplexity.ts

@@ -7,6 +7,7 @@
 import {
   getArgumentValues,
   getDirectiveValues,
+  getVariableValues,
 } from 'graphql/execution/values';
 
 import {
@@ -121,6 +122,7 @@ export default class QueryComplexity {
   estimators: Array<ComplexityEstimator>;
   includeDirectiveDef: GraphQLDirective;
   skipDirectiveDef: GraphQLDirective;
+  variableValues: Record<string, any>;
 
   constructor(context: ValidationContext, options: QueryComplexityOptions) {
     if (
@@ -139,6 +141,7 @@ export default class QueryComplexity {
     this.includeDirectiveDef = this.context.getSchema().getDirective('include');
     this.skipDirectiveDef = this.context.getSchema().getDirective('skip');
     this.estimators = options.estimators;
+    this.variableValues = {};
 
     this.OperationDefinition = {
       enter: this.onOperationDefinitionEnter,
@@ -154,6 +157,14 @@ export default class QueryComplexity {
       return;
     }
 
+    // Get variable values from variables that are passed from options, merged
+    // with default values defined in the operation
+    this.variableValues = getVariableValues(
+      this.context.getSchema(),
+      operation.variableDefinitions ?? [],
+      this.options.variables ?? {}
+    ).coerced;
+
     switch (operation.operation) {
       case 'query':
         this.complexity += this.nodeComplexity(
@@ -246,7 +257,7 @@ export default class QueryComplexity {
                 const values = getDirectiveValues(
                   this.includeDirectiveDef,
                   childNode,
-                  this.options.variables || {}
+                  this.variableValues || {}
                 );
                 includeNode = values.if;
                 break;
@@ -255,7 +266,7 @@ export default class QueryComplexity {
                 const values = getDirectiveValues(
                   this.skipDirectiveDef,
                   childNode,
-                  this.options.variables || {}
+                  this.variableValues || {}
                 );
                 skipNode = values.if;
                 break;
@@ -282,7 +293,7 @@ export default class QueryComplexity {
                 args = getArgumentValues(
                   field,
                   childNode,
-                  this.options.variables || {}
+                  this.variableValues || {}
                 );
               } catch (e) {
                 return this.context.reportError(e);

src/__tests__/QueryComplexity-test.ts

@@ -37,6 +37,21 @@ describe('QueryComplexity analysis', () => {
     expect(complexity).to.equal(1);
   });
 
+  it('should respect @include(if: false) via default variable value', () => {
+    const ast = parse(`
+      query Foo ($shouldSkip: Boolean = false) {
+        variableScalar(count: 10) @include(if: $shouldSkip)
+      }
+    `);
+
+    const complexity = getComplexity({
+      estimators: [simpleEstimator({ defaultComplexity: 1 })],
+      schema,
+      query: ast,
+    });
+    expect(complexity).to.equal(0);
+  });
+
   it('should respect @include(if: false)', () => {
     const ast = parse(`
       query {
@@ -133,6 +148,25 @@ describe('QueryComplexity analysis', () => {
     expect(complexity).to.equal(50);
   });
 
+  it('should calculate complexity with variables and default value', () => {
+    const ast = parse(`
+      query Q($count: Int = 5) {
+        variableScalar(count: $count)
+      }
+    `);
+
+    const complexity = getComplexity({
+      estimators: [
+        fieldExtensionsEstimator(),
+        simpleEstimator({ defaultComplexity: 1 }),
+      ],
+      schema,
+      query: ast,
+      variables: {},
+    });
+    expect(complexity).to.equal(50);
+  });
+
   it('should not allow negative cost', () => {
     const ast = parse(`
       query {