From 7579b81b978f4ed5240a7eb0b70c3fb8bdad5abd Mon Sep 17 00:00:00 2001
From: Lorenzo Blasa <lblasa@fb.com>
Date: Mon, 17 Jan 2022 09:56:36 -0800
Subject: [PATCH] Add a bit of defence checks as to minimise exception
 likelihood when no medium is known

Summary:
^

Changelog: Minimises the probability of throwing an exception if no exchange medium is known

Reviewed By: passy

Differential Revision: D33620655

fbshipit-source-id: e03e7fed0607c376add218ee98dcd2bd0f8880f1
---
 xplat/Flipper/ConnectionContextStore.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/xplat/Flipper/ConnectionContextStore.cpp b/xplat/Flipper/ConnectionContextStore.cpp
index a19f0d82a..04f5547ab 100644
--- a/xplat/Flipper/ConnectionContextStore.cpp
+++ b/xplat/Flipper/ConnectionContextStore.cpp
@@ -114,9 +114,16 @@ std::string ConnectionContextStore::getDeviceId() {
 folly::Optional<FlipperCertificateExchangeMedium>
 ConnectionContextStore::getLastKnownMedium() {
   try {
-    std::string config =
-        loadStringFromFile(absoluteFilePath(CONNECTION_CONFIG_FILE));
-    auto maybeMedium = folly::parseJson(config)["medium"];
+    auto configurationFilePath = absoluteFilePath(CONNECTION_CONFIG_FILE);
+    if (!fileExists(configurationFilePath)) {
+      return folly::none;
+    }
+    std::string data = loadStringFromFile(configurationFilePath);
+    auto config = folly::parseJson(data);
+    if (config.count("medium") == 0) {
+      return folly::none;
+    }
+    auto maybeMedium = config["medium"];
     return maybeMedium.isInt()
         ? folly::Optional<FlipperCertificateExchangeMedium>{static_cast<
               FlipperCertificateExchangeMedium>(maybeMedium.getInt())}