add a rule to capitalize named operations

README.md

@@ -399,6 +399,50 @@ module.exports = {
   ]
 }
 ```
+
+### Capitalization of a first letter of Named Operation rule
+
+The Capitalize Named Operation rule validates that all existing operation names are capitalized.
+
+**Pass**
+```
+query FetchUsername {
+  viewer {
+    name
+  }
+}
+```
+
+**Fail**
+```
+query fetchUsername {
+  viewer {
+    name
+  }
+}
+```
+
+The rule is defined as `graphql/capitalized-named-operations`.
+
+```js
+// In a file called .eslintrc.js
+module.exports = {
+  parser: "babel-eslint",
+  rules: {
+    "graphql/template-strings": ['error', {
+      env: 'apollo',
+      schemaJson: require('./schema.json'),
+    }],
+    "graphql/capitalized-named-operations": ['warn', {
+      schemaJson: require('./schema.json'),
+    }],
+  },
+  plugins: [
+    'graphql'
+  ]
+}
+```
+
 ### Required Fields Validation Rule
 
 The Required Fields rule validates that any specified required field is part of the query, but only if that field is available in schema. This is useful to ensure that query results are cached properly in the client.

src/customGraphQLValidationRules.js

@@ -1,5 +1,17 @@
 import { GraphQLError, getNamedType } from "graphql";
 
+export function OperationNamesMustBeCapitalized(context) {
+  return {
+    OperationDefinition(node) {
+      if (node.name && node.name.value && (node.name.value[0] == node.name.value[0].toLowerCase())) {
+        context.reportError(
+          new GraphQLError("All operations must be capitalized", [node])
+        );
+      }
+    }
+  };
+}
+
 export function OperationsMustHaveNames(context) {
   return {
     OperationDefinition(node) {

src/index.js

@@ -178,6 +178,29 @@ export const rules = {
       );
     }
   },
+  "capitalized-named-operations": {
+    meta: {
+      schema: {
+        type: "array",
+        items: {
+          additionalProperties: false,
+          properties: { ...defaultRuleProperties },
+          ...schemaPropsExclusiveness
+        }
+      }
+    },
+    create: context => {
+      return createRule(context, optionGroup =>
+        parseOptions(
+          {
+            validators: ["OperationNamesMustBeCapitalized"],
+            ...optionGroup
+          },
+          context
+        )
+      );
+    }
+  },
   "required-fields": {
     meta: {
       schema: {

test/validationRules/capitalized-named-operations.js

@@ -0,0 +1,41 @@
+import { rules } from "../../src";
+import schemaJson from "../schema.json";
+
+import { ruleTester, parserOptions } from "../helpers";
+
+const capitalizedNamedOperationsValidatorCases = {
+  pass: [
+    "const x = gql`query Test { sum(a: 1, b: 2) }`",
+    "const x = gql`query { sum(a: 1, b: 2) }`",
+  ],
+  fail: [{
+    code: "const x = gql`query test { sum(a: 1, b: 2) }`",
+    errors: [
+      {
+        message: "All operations must be capitalized",
+        type: "TaggedTemplateExpression"
+      }
+    ]
+  }]
+};
+
+// Validate the named-operations rule
+const options = [
+  {
+    schemaJson,
+    tagName: "gql"
+  }
+];
+ruleTester.run("testing capitalized-named-operations rule", rules["capitalized-named-operations"], {
+  valid: capitalizedNamedOperationsValidatorCases.pass.map(code => ({
+    options,
+    parserOptions,
+    code
+    })),
+  invalid: capitalizedNamedOperationsValidatorCases.fail.map(({ code, errors }) => ({
+    options,
+    parserOptions,
+    code,
+    errors
+  }))
+});

test/validationRules/index.js

@@ -1,4 +1,5 @@
 import './named-operations';
+import './capitalized-named-operations';
 import './required-fields';
 import './no-deprecated-fields';
 import './capitalized-type-name';