fix(config): validate unique fields names under the same level (#3804)

packages/netlify-cms-core/package.json

@@ -27,6 +27,7 @@
     "@iarna/toml": "2.2.5",
     "ajv": "^6.10.0",
     "ajv-errors": "^1.0.1",
+    "ajv-keywords": "^3.4.1",
     "copy-text-to-clipboard": "^2.0.0",
     "diacritics": "^1.3.0",
     "fuzzy": "^0.1.1",

packages/netlify-cms-core/src/constants/__tests__/configSchema.spec.js

@@ -182,5 +182,44 @@ describe('config', () => {
         validateConfig(merge({}, validConfig, { collections: [{ sortableFields: [] }] }));
       }).not.toThrow();
     });
+
+    it('should throw if collection fields names are not unique', () => {
+      expect(() => {
+        validateConfig(
+          merge(validConfig, {
+            collections: [
+              {
+                fields: [
+                  { name: 'title', label: 'title', widget: 'string' },
+                  { name: 'title', label: 'other title', widget: 'string' },
+                ],
+              },
+            ],
+          }),
+        );
+      }).toThrowError("'collections[0].fields' fields names must be unique");
+    });
+
+    it('should not throw if collection fields are unique across nesting levels', () => {
+      expect(() => {
+        validateConfig(
+          merge(validConfig, {
+            collections: [
+              {
+                fields: [
+                  { name: 'title', label: 'title', widget: 'string' },
+                  {
+                    name: 'object',
+                    label: 'Object',
+                    widget: 'object',
+                    fields: [{ name: 'title', label: 'title', widget: 'string' }],
+                  },
+                ],
+              },
+            ],
+          }),
+        );
+      }).not.toThrow();
+    });
   });
 });

packages/netlify-cms-core/src/constants/configSchema.js

@@ -1,4 +1,5 @@
 import AJV from 'ajv';
+import uniqueItemProperties from 'ajv-keywords/keywords/uniqueItemProperties';
 import ajvErrors from 'ajv-errors';
 import { formatExtensions, frontmatterFormats, extensionFormatters } from 'Formats/formats';
 
@@ -19,6 +20,7 @@ const fieldsConfig = {
     },
     required: ['name'],
   },
+  uniqueItemProperties: ['name'],
 };
 
 const viewFilters = {
@@ -223,11 +225,20 @@ class ConfigError extends Error {
  */
 export function validateConfig(config) {
   const ajv = new AJV({ allErrors: true, jsonPointers: true });
+  uniqueItemProperties(ajv);
   ajvErrors(ajv);
 
   const valid = ajv.validate(getConfigSchema(), config);
   if (!valid) {
-    console.error('Config Errors', ajv.errors);
-    throw new ConfigError(ajv.errors);
+    const errors = ajv.errors.map(e => {
+      // TODO: remove after https://github.com/ajv-validator/ajv-keywords/pull/123 is merged
+      if (e.keyword === 'uniqueItemProperties') {
+        const newError = { ...e, message: 'fields names must be unique' };
+        return newError;
+      }
+      return e;
+    });
+    console.error('Config Errors', errors);
+    throw new ConfigError(errors);
   }
 }