Only compute component stacks in DEV and prerenders

Author: sebmarkbage

packages/react-server/src/ReactFizzServer.js

@@ -765,12 +765,27 @@ type ThrownInfo = {
 export type ErrorInfo = ThrownInfo;
 export type PostponeInfo = ThrownInfo;
 
+type ThrownInfo = {
+  componentStack?: string,
+};
+export type ErrorInfo = ThrownInfo;
+export type PostponeInfo = ThrownInfo;
+
 // While we track component stacks in prod all the time we only produce a reified stack in dev and
 // during prerender in Prod. The reason for this is that the stack is useful for prerender where the timeliness
 // of the request is less critical than the observability of the execution. For renders and resumes however we
 // prioritize speed of the request.
-function getThrownInfo(node: null | ComponentStackNode): ThrownInfo {
-  if (node) {
+function getThrownInfo(
+  request: Request,
+  node: null | ComponentStackNode,
+): ThrownInfo {
+  if (
+    node &&
+    // Always produce a stack in dev
+    (__DEV__ ||
+      // Produce a stack in prod if we're in a prerender
+      request.trackedPostpones !== null)
+  ) {
     return {
       componentStack: getStackFromNode(node),
     };