create separate types for before and after deleting sentry property

Author: lobsterkatie

packages/nextjs/src/config/index.ts

@@ -16,13 +16,15 @@ export function withSentryConfig(
   // `defaults` in order to pass them along to the user's function
   if (typeof exportedUserNextConfig === 'function') {
     return function (phase: string, defaults: { defaultConfig: NextConfigObject }): NextConfigObject {
-      const userNextConfigObject = exportedUserNextConfig(phase, defaults);
+      let userNextConfigObject = exportedUserNextConfig(phase, defaults);
 
       // Next 12.2.3+ warns about non-canonical properties on `userNextConfig`, so grab and then remove the `sentry`
       // property there. Where we actually need it is in the webpack config function we're going to create, so pass it
       // to `constructWebpackConfigFunction` so that it will be in the created function's closure.
       const { sentry: userSentryOptions } = userNextConfigObject;
       delete userNextConfigObject.sentry;
+      // Remind TS that there's now no `sentry` property
+      userNextConfigObject = userNextConfigObject as NextConfigObject;
 
       return {
         ...userNextConfigObject,
@@ -41,9 +43,11 @@ export function withSentryConfig(
   // for a more thorough explanation of what we're doing here.)
   const { sentry: userSentryOptions } = exportedUserNextConfig;
   delete exportedUserNextConfig.sentry;
+  // Remind TS that there's now no `sentry` property
+  const userNextConfigObject = exportedUserNextConfig as NextConfigObject;
 
   return {
-    ...exportedUserNextConfig,
-    webpack: constructWebpackConfigFunction(exportedUserNextConfig, userSentryWebpackPluginOptions, userSentryOptions),
+    ...userNextConfigObject,
+    webpack: constructWebpackConfigFunction(userNextConfigObject, userSentryWebpackPluginOptions, userSentryOptions),
   };
 }

packages/nextjs/src/config/types.ts

@@ -8,7 +8,18 @@ export type SentryWebpackPlugin = WebpackPluginInstance & { options: SentryWebpa
  * Overall Nextjs config
  */
 
-export type ExportedNextConfig = NextConfigObject | NextConfigFunction;
+// The first argument to `withSentryConfig` (which is the user's next config) may contain a `sentry` key, which we'll
+// remove once we've captured it, in order to prevent nextjs from throwing warnings. Since it's only in there
+// temporarily, we don't include it in the main `NextConfigObject` or `NextConfigFunction` types.
+export type ExportedNextConfig = NextConfigObjectWithSentry | NextConfigFunctionWithSentry;
+
+type NextConfigObjectWithSentry = NextConfigObject & {
+  sentry?: UserSentryOptions;
+};
+type NextConfigFunctionWithSentry = (
+  phase: string,
+  defaults: { defaultConfig: NextConfigObject },
+) => NextConfigObjectWithSentry;
 
 export type NextConfigObject = {
   // custom webpack options
@@ -21,7 +32,9 @@ export type NextConfigObject = {
   basePath?: string;
   // config which will be available at runtime
   publicRuntimeConfig?: { [key: string]: unknown };
-  sentry?: UserSentryOptions;
+  // enforce the fact that we pull this property out and after that it's gone (see note by
+  // `NextConfigObjectWithSentry` type above )
+  sentry?: never;
 };
 
 export type UserSentryOptions = {