fix: tracing root use appDir as fallback (#2136)

* fix: add default values for relativeAppDir and outputFileTracingRoot

* fix: use `appDir` as fallback

* fix: add optional for potetially undefined variable

* fix: apparently not.toReject doesn't exist in newer versions of Jest

* fix: oops, order of paths was swapped!

* fix: toResolve is not a function

* fix: why do all these assertions not exist?

Author: Skn0tt

packages/runtime/src/helpers/functions.ts

@@ -229,14 +229,14 @@ export const setupImageFunction = async ({
 }
 
 const traceRequiredServerFiles = async (publish: string): Promise<string[]> => {
-  const {
-    files,
-    relativeAppDir,
-    config: {
-      experimental: { outputFileTracingRoot },
-    },
-  } = await getRequiredServerFiles(publish)
-  const appDirRoot = join(outputFileTracingRoot, relativeAppDir)
+  const requiredServerFiles = await getRequiredServerFiles(publish)
+
+  let appDirRoot = requiredServerFiles.appDir ?? join(publish, '..')
+  if (requiredServerFiles.relativeAppDir && requiredServerFiles.config?.experimental.outputFileTracingRoot) {
+    appDirRoot = join(requiredServerFiles.config.experimental.outputFileTracingRoot, requiredServerFiles.relativeAppDir)
+  }
+
+  const files = requiredServerFiles.files ?? []
   const absoluteFiles = files.map((file) => join(appDirRoot, file))
 
   absoluteFiles.push(join(publish, 'required-server-files.json'))

test/index.spec.ts

@@ -737,6 +737,28 @@ describe('onBuild()', () => {
 
     expect(netlifyConfig.functions['_api_*'].node_bundler).toEqual('nft')
   })
+
+  // eslint-disable-next-line jest/expect-expect
+  it('works when `relativeAppDir` is undefined', async () => {
+    await moveNextDist()
+
+    const initialConfig = await getRequiredServerFiles(netlifyConfig.build.publish)
+    delete initialConfig.relativeAppDir
+    await updateRequiredServerFiles(netlifyConfig.build.publish, initialConfig)
+
+    await nextRuntime.onBuild(defaultArgs)
+  })
+
+  // eslint-disable-next-line jest/expect-expect
+  it('works when `outputFileTracingRoot` is undefined', async () => {
+    await moveNextDist()
+
+    const initialConfig = await getRequiredServerFiles(netlifyConfig.build.publish)
+    delete initialConfig.config.experimental.outputFileTracingRoot
+    await updateRequiredServerFiles(netlifyConfig.build.publish, initialConfig)
+
+    await nextRuntime.onBuild(defaultArgs)
+  })
 })
 
 describe('onPostBuild', () => {