From 58e5ec69e06d44b72725d9f6c39a293e26b27309 Mon Sep 17 00:00:00 2001
From: Artem Chikin <achikin@apple.com>
Date: Fri, 25 Jun 2021 16:48:54 -0700
Subject: [PATCH] Do not emit a dependency-scanner fallback warning when in
 integrated-driver mode

This warning is mostly useful for debugging the driver, so let's hide it when libSwiftDriver is used, instead of a swift-driver executable.
There are also valid scenarios where the scanning action can succeed just-as-well using the fallback path where this warning is extraneous and may confuse users because it is not actionable.
---
 .../ExplicitModuleBuilds/ModuleDependencyScanning.swift     | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift b/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift
index 7d31c9479..38b78efa6 100644
--- a/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift
+++ b/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift
@@ -105,7 +105,11 @@ public extension Driver {
         .verifyOrCreateScannerInstance(fileSystem: fileSystem,
                                        swiftScanLibPath: scanLibPath) == false {
       fallbackToFrontend = true
-      diagnosticEngine.emit(.warn_scanner_frontend_fallback())
+      // This warning is mostly useful for debugging the driver, so let's hide it
+      // when libSwiftDriver is used, instead of a swift-driver executable.
+      if !integratedDriver {
+        diagnosticEngine.emit(.warn_scanner_frontend_fallback())
+      }
     }
     return fallbackToFrontend
   }