Mutate "less destructively"

The value that is sometimes mutated by addCucumberPreprocessorPlugin(),
is read by compile() as it attempts to calculate a common ancestor
path of all the files.

It would erroneously use the filtered specs to determine this value and
this obviously adversely affected the ability to resolve step
definitions.

This fixes #785.

Author: badeball

CHANGELOG.md

@@ -8,6 +8,8 @@ All notable changes to this project will be documented in this file.
 
 - Correct some path handling on Windows, fixes [#788](https://github.com/badeball/cypress-cucumber-preprocessor/issues/788).
 
+- Correct calculation of common ancestor path, even when specs are filtered, fixes [#785](https://github.com/badeball/cypress-cucumber-preprocessor/issues/785).
+
 ## v12.0.0
 
 Breaking changes:

features/issues/785.feature

@@ -0,0 +1,42 @@
+# https://github.com/badeball/cypress-cucumber-preprocessor/issues/785
+
+Feature: omit filtered tests, creating a different common ancestor path
+  Background:
+    Given additional preprocessor configuration
+      """
+      {
+        "stepDefinitions": "cypress/e2e/[filepath].js",
+        "filterSpecs": true
+      }
+      """
+    And a file named "cypress/e2e/foo/bar.feature" with:
+      """
+      Feature: a feature
+        Scenario: a scenario
+          Given a step
+      """
+    And a file named "cypress/e2e/foo/bar.js" with:
+      """
+      const { Given } = require("@badeball/cypress-cucumber-preprocessor");
+      Given("a step", () => {})
+      """
+    And a file named "cypress/e2e/baz/qux.feature" with:
+      """
+      @qux
+      Feature: a feature
+        Scenario: a scenario
+          Given a step
+      """
+    And a file named "cypress/e2e/baz/qux.js" with:
+      """
+      const { Given } = require("@badeball/cypress-cucumber-preprocessor");
+      Given("a step", () => {})
+      """
+
+  Scenario: no filtering
+    When I run cypress
+    Then it passes
+
+  Scenario: with filtering
+    When I run cypress with "--env tags=@qux"
+    Then it passes

lib/add-cucumber-preprocessor-plugin.ts

@@ -27,6 +27,7 @@ import {
 
 import {
   HOOK_FAILURE_EXPR,
+  INTERNAL_PROPERTY_NAME,
   TASK_APPEND_MESSAGES,
   TASK_CREATE_STRING_ATTACHMENT,
   TASK_TEST_STEP_STARTED,
@@ -268,6 +269,29 @@ type AddOptions = {
   omitAfterScreenshotHandler?: boolean;
 };
 
+type PreservedPluginConfigOptions = ICypressConfiguration & {
+  [INTERNAL_PROPERTY_NAME]?: Partial<ICypressConfiguration>;
+};
+
+export function mutateConfigObjectPreservingly<
+  K extends keyof ICypressConfiguration
+>(
+  config: PreservedPluginConfigOptions,
+  property: K,
+  value: PreservedPluginConfigOptions[K]
+) {
+  const preserved =
+    config[INTERNAL_PROPERTY_NAME] ?? (config[INTERNAL_PROPERTY_NAME] = {});
+  preserved[property] = config[property];
+  config[property] = value;
+}
+
+export function rebuildOriginalConfigObject(
+  config: PreservedPluginConfigOptions
+): ICypressConfiguration {
+  return Object.assign({}, config, config[INTERNAL_PROPERTY_NAME]);
+}
+
 export default async function addCucumberPreprocessorPlugin(
   on: Cypress.PluginEvents,
   config: Cypress.PluginConfigOptions,
@@ -345,9 +369,7 @@ export default async function addCucumberPreprocessorPlugin(
   if (tags !== null && preprocessor.filterSpecs) {
     const node = parse(tags);
 
-    const propertyName = "specPattern" in config ? "specPattern" : "testFiles";
-
-    (config as any)[propertyName] = getTestFiles(
+    const testFiles = getTestFiles(
       config as unknown as ICypressConfiguration
     ).filter((testFile) => {
       const content = syncFs.readFileSync(testFile).toString("utf-8");
@@ -374,6 +396,14 @@ export default async function addCucumberPreprocessorPlugin(
         node.evaluate(pickle.tags?.map((tag) => tag.name).filter(notNull) ?? [])
       );
     });
+
+    const propertyName = "specPattern" in config ? "specPattern" : "testFiles";
+
+    mutateConfigObjectPreservingly(
+      config,
+      propertyName as keyof ICypressConfiguration,
+      testFiles
+    );
   }
 
   return config;

lib/template.ts

@@ -24,6 +24,8 @@ import { notNull } from "./type-guards";
 
 import { ensureIsRelative } from "./helpers";
 
+import { rebuildOriginalConfigObject } from "./add-cucumber-preprocessor-plugin";
+
 const { stringify } = JSON;
 
 export async function compile(
@@ -32,6 +34,8 @@ export async function compile(
   data: string,
   uri: string = this.resourcePath
 ) {
+  configuration = rebuildOriginalConfigObject(configuration);
+
   const options = {
     includeSource: false,
     includeGherkinDocument: true,