[Flight] Clarify that location field is a FunctionLocation not a CallSite (facebook#33141)

Follow up to facebook#33136.

This clarifies in the types where the conversion happens from a CallSite
which we use to simulate getting the enclosing line/col to a
FunctionLocation which doesn't represent a CallSite but actually just
the function which only has an enclosing line/col.

Author: sebmarkbage

packages/react-client/src/ReactFlightClient.js

@@ -15,7 +15,7 @@ import type {
   ReactAsyncInfo,
   ReactTimeInfo,
   ReactStackTrace,
-  ReactCallSite,
+  ReactFunctionLocation,
   ReactErrorInfoDev,
 } from 'shared/ReactTypes';
 import type {LazyComponent} from 'react/src/ReactLazy';
@@ -1074,7 +1074,7 @@ function loadServerReference<A: Iterable<any>, T>(
     bound: null | Thenable<Array<any>>,
     name?: string, // DEV-only
     env?: string, // DEV-only
-    location?: ReactCallSite, // DEV-only
+    location?: ReactFunctionLocation, // DEV-only
   },
   parentObject: Object,
   key: string,

packages/react-client/src/ReactFlightReplyClient.js

@@ -13,7 +13,7 @@ import type {
   FulfilledThenable,
   RejectedThenable,
   ReactCustomFormAction,
-  ReactCallSite,
+  ReactFunctionLocation,
 } from 'shared/ReactTypes';
 import type {LazyComponent} from 'react/src/ReactLazy';
 import type {TemporaryReferenceSet} from './ReactFlightTemporaryReferences';
@@ -1248,7 +1248,7 @@ export function createBoundServerReference<A: Iterable<any>, T>(
     bound: null | Thenable<Array<any>>,
     name?: string, // DEV-only
     env?: string, // DEV-only
-    location?: ReactCallSite, // DEV-only
+    location?: ReactFunctionLocation, // DEV-only
   },
   callServer: CallServerCallback,
   encodeFormAction?: EncodeFormActionCallback,
@@ -1309,7 +1309,7 @@ const v8FrameRegExp =
 // filename:0:0
 const jscSpiderMonkeyFrameRegExp = /(?:(.*)@)?(.*):(\d+):(\d+)/;
 
-function parseStackLocation(error: Error): null | ReactCallSite {
+function parseStackLocation(error: Error): null | ReactFunctionLocation {
   // This parsing is special in that we know that the calling function will always
   // be a module that initializes the server action. We also need this part to work
   // cross-browser so not worth a Config. It's DEV only so not super code size
@@ -1354,7 +1354,7 @@ function parseStackLocation(error: Error): null | ReactCallSite {
   const line = +(parsed[3] || parsed[6]);
   const col = +(parsed[4] || parsed[7]);
 
-  return [name, filename, line, col, line, col];
+  return [name, filename, line, col];
 }
 
 export function createServerReference<A: Iterable<any>, T>(

packages/react-server/src/ReactFlightServer.js

@@ -62,7 +62,7 @@ import type {
   ReactAsyncInfo,
   ReactTimeInfo,
   ReactStackTrace,
-  ReactCallSite,
+  ReactFunctionLocation,
   ReactErrorInfo,
   ReactErrorInfoDev,
 } from 'shared/ReactTypes';
@@ -2089,7 +2089,7 @@ function serializeServerReference(
   const bound = boundArgs === null ? null : Promise.resolve(boundArgs);
   const id = getServerReferenceId(request.bundlerConfig, serverReference);
 
-  let location: null | ReactCallSite = null;
+  let location: null | ReactFunctionLocation = null;
   if (__DEV__) {
     const error = getServerReferenceLocation(
       request.bundlerConfig,
@@ -2098,7 +2098,13 @@ function serializeServerReference(
     if (error) {
       const frames = parseStackTrace(error, 1);
       if (frames.length > 0) {
-        location = frames[0];
+        const firstFrame = frames[0];
+        location = [
+          firstFrame[0],
+          firstFrame[1],
+          firstFrame[2], // The line and col of the callsite represents the
+          firstFrame[3], // enclosing line and col of the function.
+        ];
       }
     }
   }
@@ -2108,7 +2114,7 @@ function serializeServerReference(
     bound: null | Promise<Array<any>>,
     name?: string, // DEV-only
     env?: string, // DEV-only
-    location?: ReactCallSite, // DEV-only
+    location?: ReactFunctionLocation, // DEV-only
   } =
     __DEV__ && location !== null
       ? {

packages/shared/ReactTypes.js

@@ -192,6 +192,13 @@ export type ReactCallSite = [
 
 export type ReactStackTrace = Array<ReactCallSite>;
 
+export type ReactFunctionLocation = [
+  string, // function name
+  string, // file name TODO: model nested eval locations as nested arrays
+  number, // enclosing line number
+  number, // enclosing column number
+];
+
 export type ReactComponentInfo = {
   +name: string,
   +env?: string,