From 2132a9034dd823c5844792551cef81f3e86adaf3 Mon Sep 17 00:00:00 2001
From: Xi Ge <xi_ge@apple.com>
Date: Wed, 28 Jul 2021 17:32:21 -0700
Subject: [PATCH] DependenciesScanner: include -sdk in Swift module building
 command

Swift module building commands need -sdk because dependencies sometimes use
sdk-relative paths (prebuilt modules for example). Without -sdk, the command
will not be able to local these dependencies, leading to unnecessary
rebuilding from textual interfaces.

rdar://81177968
---
 lib/Frontend/ModuleInterfaceLoader.cpp             |  7 +++++++
 test/ScanDependencies/include-sdk-in-command.swift | 11 +++++++++++
 test/ScanDependencies/module_deps.swift            |  1 -
 3 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 test/ScanDependencies/include-sdk-in-command.swift

diff --git a/lib/Frontend/ModuleInterfaceLoader.cpp b/lib/Frontend/ModuleInterfaceLoader.cpp
index 8f3f1448f1b73..13ff2e7798313 100644
--- a/lib/Frontend/ModuleInterfaceLoader.cpp
+++ b/lib/Frontend/ModuleInterfaceLoader.cpp
@@ -1290,6 +1290,13 @@ void InterfaceSubContextDelegateImpl::inheritOptionsForBuildingInterface(
   genericSubInvocation.setImportSearchPaths(SearchPathOpts.ImportSearchPaths);
   genericSubInvocation.setFrameworkSearchPaths(SearchPathOpts.FrameworkSearchPaths);
   if (!SearchPathOpts.SDKPath.empty()) {
+    // Add -sdk arguments to the module building commands.
+    // Module building commands need this because dependencies sometimes use
+    // sdk-relative paths (prebuilt modules for example). Without -sdk, the command
+    // will not be able to local these dependencies, leading to unnecessary
+    // building from textual interfaces.
+    GenericArgs.push_back("-sdk");
+    GenericArgs.push_back(ArgSaver.save(SearchPathOpts.SDKPath));
     genericSubInvocation.setSDKPath(SearchPathOpts.SDKPath);
   }
 
diff --git a/test/ScanDependencies/include-sdk-in-command.swift b/test/ScanDependencies/include-sdk-in-command.swift
new file mode 100644
index 0000000000000..eefe5a51c21fb
--- /dev/null
+++ b/test/ScanDependencies/include-sdk-in-command.swift
@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -scan-dependencies %s -o %t/deps.json -sdk %t/mysecretsdk.sdk
+
+// Check the contents of the JSON output
+// RUN: %FileCheck %s < %t/deps.json
+
+func foo() { print(1) }
+
+// CHECK: "-sdk",
+// CHECK-NEXT: mysecretsdk.sdk
diff --git a/test/ScanDependencies/module_deps.swift b/test/ScanDependencies/module_deps.swift
index e39f376020e5e..c9c46e435991e 100644
--- a/test/ScanDependencies/module_deps.swift
+++ b/test/ScanDependencies/module_deps.swift
@@ -213,7 +213,6 @@ import SubE
 /// --------Clang module SwiftShims
 // CHECK-LABEL: "modulePath": "SwiftShims.pcm",
 
-// CHECK-NO-SEARCH-PATHS-NOT: "-sdk"
 // CHECK-NO-SEARCH-PATHS-NOT: "-prebuilt-module-cache-path"
 
 // Check make-style dependencies