[Dependency Scanning] Remove Unnecessary Code that Computes Module Output Path (#79752)

#79297 implemented current working directory pruning but left some unnecessary code
that computes Swift interface module output path prematurely. This PR removes the code that computes the output path too 
early. The `ExplicitModuleDependencyResolver` now adds the path to the command line after it can correctly compute it. 

Context: https://github.com/swiftlang/swift/pull/79297/files#r1955314542

Author: qiongsiwu

lib/DependencyScan/ScanDependencies.cpp

@@ -172,7 +172,7 @@ class ExplicitModuleDependencyResolver {
     SwiftInterfaceModuleOutputPathResolution::ResultTy swiftInterfaceOutputPath;
     if (resolvingDepInfo.isSwiftInterfaceModule()) {
       pruneUnusedVFSOverlay(swiftInterfaceOutputPath);
-      updateSwiftInterfaceModuleOutputPath(swiftInterfaceOutputPath);
+      addSwiftInterfaceModuleOutputPathToCommandLine(swiftInterfaceOutputPath);
     }
 
     // Update the dependency in the cache with the modified command-line.
@@ -455,19 +455,12 @@ class ExplicitModuleDependencyResolver {
     return;
   }
 
-  void updateSwiftInterfaceModuleOutputPath(
+  void addSwiftInterfaceModuleOutputPathToCommandLine(
       const SwiftInterfaceModuleOutputPathResolution::ResultTy &outputPath) {
     StringRef outputName = outputPath.outputPath.str();
 
-    bool isOutputPath = false;
-    for (auto &A : commandline) {
-      if (isOutputPath) {
-        A = outputName.str();
-        break;
-      } else if (A == "-o") {
-        isOutputPath = true;
-      }
-    }
+    commandline.push_back("-o");
+    commandline.push_back(outputName.str());
 
     return;
   }

lib/Serialization/ScanningLoaders.cpp

@@ -205,15 +205,6 @@ SwiftModuleScanner::scanInterfaceFile(Twine moduleInterfacePath,
           Args.push_back(candidate);
         }
 
-        // Compute the output path and add it to the command line
-        SmallString<128> outputPathBase(moduleOutputPath);
-        llvm::sys::path::append(
-            outputPathBase,
-            moduleName.str() + "-" + Hash + "." +
-                file_types::getExtension(file_types::TY_SwiftModuleFile));
-        Args.push_back("-o");
-        Args.push_back(outputPathBase.str().str());
-
         // Open the interface file.
         auto &fs = *Ctx.SourceMgr.getFileSystem();
         auto interfaceBuf = fs.getBufferForFile(moduleInterfacePath);
@@ -251,11 +242,6 @@ SwiftModuleScanner::scanInterfaceFile(Twine moduleInterfacePath,
             InPath, compiledCandidatesRefs, ArgsRefs, {}, {}, linkLibraries,
             isFramework, isStatic, {}, /*module-cache-key*/ "", UserModVer);
 
-        // We do NOT need the code below to set output path in the dependency
-        // info because it will be calculated again later. We do not want to
-        // create output paths that do not exist in the end.
-        // Result->setOutputPathAndHash(outputPathBase.str().str(), Hash);
-
         if (Ctx.CASOpts.EnableCaching) {
           std::vector<std::string> clangDependencyFiles;
           auto clangImporter =

test/ScanDependencies/FilterClangSearchPaths.swift

@@ -28,8 +28,8 @@ import C
 // CHECK-NEXT:          "moduleInterfacePath": "{{.*}}{{/|\\}}Inputs{{/|\\}}Swift{{/|\\}}A.swiftinterface",
 // CHECK:          "commandLine": [
 // CHECK:            "-fobjc-disable-direct-methods-for-testing"
-// CHECK:            "-o",
-// CHECK-NEXT:       "{{.*}}{{/|\\}}A-{{.*}}.swiftmodule",
 // CHECK-NOT:        "/tmp/foo"
 // CHECK-NOT:        "-I/tmp/bar"
+// CHECK:            "-o",
+// CHECK-NEXT:       "{{.*}}{{/|\\}}A-{{.*}}.swiftmodule"
 // CHECK:          ]

test/ScanDependencies/ObjCStrict.swift

@@ -29,7 +29,7 @@ import C
 // CHECK:          "commandLine": [
 // CHECK:            "-fobjc-disable-direct-methods-for-testing"
 // CHECK:            "-o",
-// CHECK-NEXT:       "{{.*}}{{/|\\}}A-{{.*}}.swiftmodule",
+// CHECK-NEXT:       "{{.*}}{{/|\\}}A-{{.*}}.swiftmodule"
 
 
 

test/ScanDependencies/eliminate_unused_vfs.swift

@@ -79,30 +79,30 @@ import F
 // MOD-HASH-NEXT:   "swift": {
 // MOD-HASH-NEXT:   "moduleInterfacePath": "{{.*}}{{/|\\}}F.swiftinterface",
 // MOD-HASH:   "commandLine": [
-// MOD-HASH:     "-o",
-// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH:.*]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=Swift={{.*}}{{/|\\}}Swift-[[SHASH:.*]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=SwiftOnoneSupport={{.*}}{{/|\\}}SwiftOnoneSupport-[[SOSHASH:.*]].swiftmodule",
+// MOD-HASH:     "-o",
+// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH:.*]].swiftmodule"
 // MOD-HASH:     ],
 // MOD-HASH: "mainModuleName": "deps1",
 // MOD-HASH: "linkLibraries": [],
 // MOD-HASH: "details": {
 // MOD-HASH-NEXT:   "swift": {
 // MOD-HASH-NEXT:   "moduleInterfacePath": "{{.*}}{{/|\\}}F.swiftinterface",
 // MOD-HASH:   "commandLine": [
-// MOD-HASH:     "-o",
-// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=Swift={{.*}}{{/|\\}}Swift-[[SHASH]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=SwiftOnoneSupport={{.*}}{{/|\\}}SwiftOnoneSupport-[[SOSHASH]].swiftmodule",
+// MOD-HASH:     "-o",
+// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH]].swiftmodule"
 // MOD-HASH:     ],
 // MOD-HASH: "mainModuleName": "deps2",
 // MOD-HASH: "linkLibraries": [],
 // MOD-HASH: "details": {
 // MOD-HASH-NEXT:   "swift": {
 // MOD-HASH-NEXT:   "moduleInterfacePath": "{{.*}}{{/|\\}}F.swiftinterface",
 // MOD-HASH:   "commandLine": [
-// MOD-HASH:     "-o",
-// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=Swift={{.*}}{{/|\\}}Swift-[[SHASH]].swiftmodule",
 // MOD-HASH:     "-swift-module-file=SwiftOnoneSupport={{.*}}{{/|\\}}SwiftOnoneSupport-[[SOSHASH]].swiftmodule",
+// MOD-HASH:     "-o",
+// MOD-HASH-NEXT:     "{{.*}}{{/|\\}}F-[[FHASH]].swiftmodule"
 // MOD-HASH:     ],

test/ScanDependencies/explicit-swift-dependencies.swift

@@ -47,9 +47,9 @@ import F
 // CHECK-NEXT:            "-fno-implicit-modules",
 // CHECK-NEXT:            "-Xcc",
 // CHECK-NEXT:            "-fno-implicit-module-maps",
-// CHECK-NEXT:            "-o",
-// CHECK-NEXT:            "{{.*}}{{/|\\}}F-{{.*}}.swiftmodule"
 // CHECK-DAG:             "-swift-module-file=Swift={{.*}}{{/|\\}}Swift-{{.*}}.swiftmodule"
 // CHECK-DAG:             "-swift-module-file=SwiftOnoneSupport={{.*}}{{/|\\}}SwiftOnoneSupport-{{.*}}.swiftmodule"
 // CHECK-DAG:             "-fmodule-file=F={{.*}}{{/|\\}}F-{{.*}}.pcm"
 // CHECK-DAG:             "-fmodule-file=SwiftShims={{.*}}{{/|\\}}SwiftShims-{{.*}}.pcm"
+// CHECK-NEXT:            "-o",
+// CHECK-NEXT:            "{{.*}}{{/|\\}}F-{{.*}}.swiftmodule"