[savedObjects/mappings] limit valid type names (elastic#17511)

src/server/mappings/__snapshots__/index_mappings.test.js.snap

@@ -0,0 +1,5 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`server/mapping/index_mapping constructor includes the pluginId from the extension in the _ error message if defined 1`] = `"Property names _foo registered by plugin abc123 are not allowed to start with an underscore (_)"`;
+
+exports[`server/mapping/index_mapping constructor throws if any of the new properties start with _ 1`] = `"Property names _foo are not allowed to start with an underscore (_)"`;

src/server/mappings/index_mappings.js

@@ -25,10 +25,12 @@ export class IndexMappings {
     mappingExtensions.forEach(({ properties, pluginId }) => {
       const rootProperties = getRootProperties(this._dsl);
 
-
       const conflicts = Object.keys(properties)
         .filter(key => rootProperties.hasOwnProperty(key));
 
+      const illegal = Object.keys(properties)
+        .filter(key => key.startsWith('_'));
+
       if (conflicts.length) {
         const props = formatListAsProse(conflicts);
         const owner = pluginId ? `registered by plugin ${pluginId} ` : '';
@@ -37,6 +39,14 @@ export class IndexMappings {
         );
       }
 
+      if (illegal.length) {
+        const props = formatListAsProse(illegal);
+        const owner = pluginId ? `registered by plugin ${pluginId} ` : '';
+        throw new Error(
+          `Property name${props.length > 1 ? 's' : ''} ${props} ${owner}are not allowed to start with an underscore (_)`
+        );
+      }
+
       this._setProperties({
         ...rootProperties,
         ...properties

src/server/mappings/index_mappings.test.js

@@ -132,6 +132,41 @@ describe('server/mapping/index_mapping', function () {
         new IndexMappings(initialMapping, extensions);
       }).toThrowError(/plugin abc123/);
     });
+
+    it('throws if any of the new properties start with _', () => {
+      const initialMapping = {
+        root: { properties: { foo: 'bar' } }
+      };
+      const extensions = [
+        {
+          properties: {
+            _foo: 'bar'
+          }
+        }
+      ];
+
+      expect(() => {
+        new IndexMappings(initialMapping, extensions);
+      }).toThrowErrorMatchingSnapshot();
+    });
+
+    it('includes the pluginId from the extension in the _ error message if defined', () => {
+      const initialMapping = {
+        root: { properties: { foo: 'bar' } }
+      };
+      const extensions = [
+        {
+          pluginId: 'abc123',
+          properties: {
+            _foo: 'bar'
+          }
+        }
+      ];
+
+      expect(() => {
+        new IndexMappings(initialMapping, extensions);
+      }).toThrowErrorMatchingSnapshot();
+    });
   });
 
   describe('#getDsl()', () => {