feat(enforce-system-id): detect duplicate system IDs

Author: rlaffers

lib/rules/enforce-system-id.js

@@ -20,12 +20,14 @@ module.exports = {
       invalidSystemId: 'Property "systemId" should be a non-empty string.',
       systemIdNotAllowedBeforeVersion5:
         'Property "systemId" is not supported in xstate < 5.',
+      duplicateSystemId: 'The systemId "{{systemId}}" is not unique.',
     },
   },
 
   create(context) {
     const { version } = getSettings(context)
     const prefix = getSelectorPrefix(context.sourceCode)
+    const systemIds = new Set()
 
     return {
       [`${prefix}Property[key.name='invoke'] > ObjectExpression`]: (node) => {
@@ -79,8 +81,20 @@ module.exports = {
         }
       },
 
-      // TODO another check should make sure that the systemId is unique
-      // code here
+      [`${prefix}Property[key.name='invoke'] > ObjectExpression > Property[key.name="systemId"]`]:
+        (node) => {
+          if (systemIds.has(node.value.value)) {
+            context.report({
+              node,
+              messageId: 'duplicateSystemId',
+              data: { systemId: node.value.value },
+            })
+          } else {
+            systemIds.add(node.value.value)
+          }
+        },
+
+      // TODO check use of systemId in spawns
     }
   },
 }