From 040ccfe801583d6e8599ef739f0cb09ddd84e1c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Guychard?= <loic@sourcegraph.com>
Date: Fri, 29 Mar 2019 15:55:40 +0100
Subject: [PATCH] Fix withFallback to emit from main even if fallback has
 emitted

Fixes #3039

`withFallback()` used `rxjs.race()` to fallback to basic-code-intel if the language server had not emitted after 500ms. The problem is that `race()` works as follows:

> The observable to emit first is used.

This is an issue when pinning the hover tooltip, because if the basic-code-intel result is used first, the language server result will *never be used*.
---
 src/lang-go.ts | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/lang-go.ts b/src/lang-go.ts
index bafa53e..cdc41e8 100644
--- a/src/lang-go.ts
+++ b/src/lang-go.ts
@@ -22,6 +22,7 @@ import {
     combineLatest,
     ObservableInput,
     merge,
+    timer,
 } from 'rxjs'
 import {
     concatMap,
@@ -557,12 +558,14 @@ function withFallback<T>({
     fallback: ObservableInput<T>
     delayMilliseconds: number
 }): Observable<T> {
-    return race(
-        of(null).pipe(switchMap(() => from(main))),
+    const mainObservable = from(main).pipe(share())
+    return merge(
         of(null).pipe(
             delay(delayMilliseconds),
-            switchMap(() => from(fallback))
-        )
+            switchMap(() => from(fallback)),
+            takeUntil(mainObservable)
+        ),
+        mainObservable
     )
 }