feat(core): add appendPlugins command-line option (#2385)

Add `--appendPlugins` command-line option that can append plugins without overriding the (default) `plugins`. This is a way for tools to add plugins without affecting anything else.

e2e/test/jasmine-ts-node/stryker.conf.json

@@ -6,9 +6,14 @@
   "testRunner": "jasmine",
   "concurrency": 2,
   "coverageAnalysis": "perTest",
-  "reporters": ["event-recorder", "clear-text"],
+  "reporters": [
+    "event-recorder",
+    "clear-text"
+  ],
+  "appendPlugins": [
+    "@stryker-mutator/typescript-checker"
+  ],
   "plugins": [
-    "@stryker-mutator/typescript-checker",
     "@stryker-mutator/jasmine-runner"
   ]
 }

packages/api/schema/stryker-core.json

@@ -320,6 +320,14 @@
         "@stryker-mutator/*"
       ]
     },
+    "appendPlugins": {
+      "description": "A list of additional plugins you want Stryker to load (`require`) without overwriting the (default) `plugins`.",
+      "type": "array",
+      "items": {
+        "type": "string"
+      },
+      "default": []
+    },
     "reporters": {
       "description": "With reporters, you can set the reporters for stryker to use.",
       "type": "array",

packages/core/src/StrykerCli.ts

@@ -79,6 +79,11 @@ export default class StrykerCli {
       .option('--testRunner <name>', 'The name of the test runner you want to use')
       .option('--reporters <name>', 'A comma separated list of the names of the reporter(s) you want to use', list)
       .option('--plugins <listOfPlugins>', 'A list of plugins you want stryker to load (`require`).', list)
+      .option(
+        '--appendPlugins <listOfPlugions>',
+        'A list of additional plugins you want Stryker to load (`require`) without overwriting the (default) `plugins`.',
+        list
+      )
       .option('--timeoutMS <number>', 'Tweak the absolute timeout used to wait for a test runner to complete', parseInt)
       .option('--timeoutFactor <number>', 'Tweak the standard deviation relative to the normal test run of a mutated test', parseFloat)
       .option('--maxConcurrentTestRunners <n>', 'Set the number of max concurrent test runner to spawn (default: cpuCount)', parseInt)

packages/core/src/di/buildMainInjector.ts

@@ -53,6 +53,7 @@ export function createPluginResolverProvider(parent: CliOptionsProvider): Plugin
 
 function pluginDescriptorsFactory(options: StrykerOptions): readonly string[] {
   options.plugins.push(require.resolve('../reporters'));
+  options.plugins = options.plugins.concat(options.appendPlugins);
   return options.plugins;
 }
 pluginDescriptorsFactory.inject = tokens(commonTokens.options);

packages/core/test/unit/StrykerCli.spec.ts

@@ -33,6 +33,7 @@ describe(StrykerCli.name, () => {
       [['--mutate', 'foo.js,bar.js'], { mutate: ['foo.js', 'bar.js'] }],
       [['--reporters', 'foo,bar'], { reporters: ['foo', 'bar'] }],
       [['--plugins', 'foo,bar'], { plugins: ['foo', 'bar'] }],
+      [['--appendPlugins', 'foo,bar'], { appendPlugins: ['foo', 'bar'] }],
       [['--timeoutMS', '42'], { timeoutMS: 42 }],
       [['--timeoutFactor', '42'], { timeoutFactor: 42 }],
       [['--maxConcurrentTestRunners', '42'], { maxConcurrentTestRunners: 42 }],

packages/core/test/unit/config/OptionsValidator.spec.ts

@@ -73,6 +73,18 @@ describe(OptionsValidator.name, () => {
     });
   });
 
+  describe('appendPlugins', () => {
+    it('should be invalid with non-array plugins', () => {
+      breakConfig('appendPlugins', '@stryker-mutator/typescript');
+      actValidationErrors('Config option "appendPlugins" has the wrong type. It should be a array, but was a string.');
+    });
+
+    it('should be invalid with non-string array elements', () => {
+      breakConfig('appendPlugins', ['stryker-jest', 0]);
+      actValidationErrors('Config option "appendPlugins[1]" has the wrong type. It should be a string, but was a number.');
+    });
+  });
+
   describe('mutator', () => {
     it('should be invalid with non-string mutator', () => {
       (testInjector.options.mutator as any) = 1;