added no-deprecated rule

Author: dotansimha

example/.eslintrc.json

@@ -7,6 +7,7 @@
   "rules": {
     "@graphql-eslint/validate-against-schema": "error",
     "@graphql-eslint/no-anonymous-operations": "error",
-    "@graphql-eslint/no-operation-name-suffix": "error"
+    "@graphql-eslint/no-operation-name-suffix": "error",
+    "@graphql-eslint/deprecation-must-have-reason": "error"
   }
 }

packages/plugin/src/rules/deprecation-must-have-reason.ts

@@ -0,0 +1,25 @@
+import { GraphQLESLintRule, valueFromNode } from '@graphql-eslint/types';
+
+const rule: GraphQLESLintRule = {
+  meta: {},
+  create(context) {
+    return {
+      Directive(node) {
+        if (node && node.name && node.name.value === 'deprecated') {
+          const args = node.arguments || [];
+          const reasonArg = args.find(arg => arg.name && arg.name.value === 'reason');
+          const value = reasonArg ? valueFromNode(reasonArg.value, {}) : null;
+
+          if (!value) {
+            context.report({
+              node: node.name,
+              message: `Directive "@deprecated" must have a reason!`,
+            });
+          }
+        }
+      },
+    }
+  }
+}
+
+export default rule;

packages/plugin/src/rules/index.ts

@@ -1,10 +1,12 @@
 import validate from "./validate-against-schema";
 import noAnonymousOperations  from "./no-anonymous-operations";
 import noOperationNameSuffix from "./no-operation-name-suffix";
+import deprecationMustHaveReason from "./deprecation-must-have-reason";
 
 export const rules = {
   'validate-against-schema': validate,
   'no-anonymous-operations': noAnonymousOperations,
   'no-operation-name-suffix': noOperationNameSuffix,
+  'deprecation-must-have-reason': deprecationMustHaveReason
 };
 

packages/types/src/utils.ts

@@ -1,5 +1,6 @@
 import { GraphQLESlintRuleContext } from "./rule";
-import { GraphQLSchema } from 'graphql';
+import { Kind, GraphQLSchema } from 'graphql';
+import { GraphQLESTree } from "./estree-ast"; 
 
 export function requireGraphQLSchemaFromContext(
   context: GraphQLESlintRuleContext
@@ -14,3 +15,44 @@ export function requireGraphQLSchemaFromContext(
 
   return context.parserServices.schema;
 }
+
+export default function keyValMap<T, V>(
+  list: ReadonlyArray<T>,
+  keyFn: (item: T) => string,
+  valFn: (item: T) => V,
+): Record<string, V> {
+  return list.reduce((map, item) => {
+    map[keyFn(item)] = valFn(item);
+    return map;
+  }, Object.create(null));
+}
+
+export function valueFromNode(
+  valueNode: GraphQLESTree.ValueNode,
+  variables?: Record<string, any>,
+): any {
+  switch (valueNode.type) {
+    case Kind.NULL:
+      return null;
+    case Kind.INT:
+      return parseInt(valueNode.value, 10);
+    case Kind.FLOAT:
+      return parseFloat(valueNode.value);
+    case Kind.STRING:
+    case Kind.ENUM:
+    case Kind.BOOLEAN:
+      return valueNode.value;
+    case Kind.LIST:
+      return valueNode.values.map((node) =>
+        valueFromNode(node, variables),
+      );
+    case Kind.OBJECT:
+      return keyValMap(
+        valueNode.fields,
+        (field) => field.name.value,
+        (field) => valueFromNode(field.value, variables),
+      );
+    case Kind.VARIABLE:
+      return variables?.[valueNode.name.value];
+  }
+}