fix: Resolve tsconfig.json for plugins file from the plugins directory

packages/server/lib/plugins/child/run_plugins.js

@@ -181,7 +181,7 @@ module.exports = (ipc, pluginsFile, projectRoot) => {
   })
 
   if (!tsRegistered) {
-    registerTsNode(projectRoot)
+    registerTsNode(projectRoot, pluginsFile)
 
     // ensure typescript is only registered once
     tsRegistered = true

packages/server/lib/project.js

@@ -101,7 +101,7 @@ class Project extends EE {
         return scaffold.plugins(path.dirname(cfg.pluginsFile), cfg)
       }
     }).then((cfg) => {
-      registerTsNode(this.projectRoot)
+      registerTsNode(this.projectRoot, cfg.pluginsFile)
 
       return cfg
     }).then((cfg) => {

packages/server/lib/util/ts-node.js

@@ -1,23 +1,27 @@
 const debug = require('debug')('cypress:server:ts-node')
+const path = require('path')
 const tsnode = require('ts-node')
 const resolve = require('resolve')
 
-const getTsNodeOptions = (tsPath) => {
+const getTsNodeOptions = (tsPath, pluginsFile) => {
   return {
     compiler: tsPath, // use the user's installed typescript
     compilerOptions: {
       module: 'CommonJS',
     },
+    // resolves tsconfig.json starting from the plugins directory
+    // instead of the cwd (the project root)
+    dir: path.dirname(pluginsFile),
     transpileOnly: true, // transpile only (no type-check) for speed
   }
 }
 
-const registerTsNode = (projectRoot) => {
+const registerTsNode = (projectRoot, pluginsFile) => {
   try {
     const tsPath = resolve.sync('typescript', {
       basedir: projectRoot,
     })
-    const tsOptions = getTsNodeOptions(tsPath)
+    const tsOptions = getTsNodeOptions(tsPath, pluginsFile)
 
     debug('typescript path: %s', tsPath)
     debug('registering project TS with options %o', tsOptions)

packages/server/test/e2e/1_typescript_plugins_spec.ts

@@ -23,4 +23,10 @@ describe('e2e typescript in plugins file', function () {
       project: Fixtures.projectPath('ts-proj-esmoduleinterop-true'),
     })
   })
+
+  it('loads tsconfig.json from plugins directory', function () {
+    return e2e.exec(this, {
+      project: Fixtures.projectPath('ts-proj-tsconfig-in-plugins'),
+    })
+  })
 })

packages/server/test/support/fixtures/projects/ts-proj-tsconfig-in-plugins/cypress.json

@@ -0,0 +1,3 @@
+{
+  "supportFile": false
+}

packages/server/test/support/fixtures/projects/ts-proj-tsconfig-in-plugins/cypress/integration/passing_spec.ts

@@ -0,0 +1,3 @@
+it('passes', () => {
+  expect(true).to.be.true
+})

packages/server/test/support/fixtures/projects/ts-proj-tsconfig-in-plugins/cypress/plugins/index.ts

@@ -0,0 +1,6 @@
+// this tests that the tsconfig.json is loaded from the plugins directory.
+// if it isn't, the lack of "downlevelIteration" support will cause this to
+// fail at runtime with "RangeError: Invalid array length"
+[...Array(100).keys()].map((x) => `${x}`)
+
+export default () => {}

packages/server/test/support/fixtures/projects/ts-proj-tsconfig-in-plugins/cypress/plugins/tsconfig.json

@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "downlevelIteration": true
+  }
+}

packages/server/test/support/fixtures/projects/ts-proj/cypress/plugins/index.ts

@@ -1,6 +1,6 @@
 /// <reference types="cypress" />
 
-import fn from './commonjs-export-function'
+import * as fn from './commonjs-export-function'
 
 // if esModuleInterop is forced to be true, this will error // with 'fn is
 // not a function'. instead, we allow the tsconfig.json to determine the value

packages/server/test/support/fixtures/projects/ts-proj/tsconfig.json

@@ -0,0 +1 @@
+{}

packages/server/test/unit/project_spec.js

@@ -349,13 +349,15 @@ This option will not have an effect in Some-other-name. Tests that rely on web s
         const { proj, register } = setupProject('default', tsProjPath)
 
         return proj.open().then(() => {
-          expect(register).to.be.calledWith({
+          expect(register).to.be.calledWithMatch({
             transpileOnly: true,
             compiler: projTsPath,
             compilerOptions: {
               module: 'CommonJS',
             },
           })
+
+          expect(register.lastCall.args[0].dir).to.include('ts-installed/cypress/plugins')
         })
       })