Allow outputting *only* messages

This fixes #724.

features/issues/724.feature

@@ -0,0 +1,27 @@
+# https://github.com/badeball/cypress-cucumber-preprocessor/issues/724
+
+Feature: outputting merely messages
+  Scenario: enabling *only* messages
+    Given additional preprocessor configuration
+      """
+      {
+        "messages": {
+          "enabled": true
+        }
+      }
+      """
+    And a file named "cypress/integration/a.feature" with:
+      """
+      Feature: a feature
+        Scenario: a scenario
+          Given a step
+      """
+    And a file named "cypress/support/step_definitions/steps.js" with:
+      """
+      const { Given } = require("@badeball/cypress-cucumber-preprocessor");
+      Given("a step", function() {})
+      """
+    When I run cypress
+    Then it passes
+    And there should be no JSON output
+    But there should be a messages report

features/step_definitions/json_steps.ts

@@ -60,9 +60,16 @@ Given("I've ensured cucumber-json-formatter is installed", async () => {
   });
 });
 
+Then("there should be a messages report", async function () {
+  await assert.doesNotReject(
+    () => fs.access(path.join(this.tmpDir, "cucumber-messages.ndjson")),
+    "Expected there to be a messages file"
+  );
+});
+
 Then("there should be no JSON output", async function () {
   await assert.rejects(
-    () => fs.readFile(path.join(this.tmpDir, "cucumber-messages.ndjson")),
+    () => fs.readFile(path.join(this.tmpDir, "cucumber-report.json")),
     {
       code: "ENOENT",
     },

lib/add-cucumber-preprocessor-plugin.ts

@@ -69,7 +69,7 @@ export async function beforeRunHandler(config: Cypress.PluginConfigOptions) {
 export async function afterRunHandler(config: Cypress.PluginConfigOptions) {
   const preprocessor = await resolve(config.projectRoot, config.env);
 
-  if (!preprocessor.messages.enabled) {
+  if (!preprocessor.json.enabled) {
     return;
   }