Add an end-to-end test for the option to print compile jobs for module dependencies

discovered by the fast dependency scanner.

Author: artemcm

Sources/SwiftDriver/Jobs/Planning.swift

@@ -34,20 +34,14 @@ extension Driver {
   private mutating func planStandardCompile() throws -> [Job] {
     var jobs = [Job]()
 
-    // If we've been asked to prebuild module dependencies, prescan the source
-    // files to produce a module dependency graph and turn it into a set
-    // of jobs required to build all dependencies.
-    // For the time being, just prints the jobs' compile commands.
+    // If we've been asked to prebuild module dependencies,
+    // for the time being, just print the jobs' compile commands.
     if parsedOptions.contains(.driverPrintModuleDependenciesJobs) {
-      let moduleDependencyGraph = try computeModuleDependencyGraph()
+      let modulePrebuildJobs = try generateExplicitModuleBuildJobs()
       let forceResponseFiles = parsedOptions.contains(.driverForceResponseFiles)
-      if let dependencyGraph = moduleDependencyGraph {
-        let modulePrebuildJobs =
-              try planExplicitModuleDependenciesCompile(dependencyGraph: dependencyGraph)
-        for job in modulePrebuildJobs {
-          try Self.printJob(job, resolver: try ArgsResolver(),
-                            forceResponseFiles: forceResponseFiles)
-        }
+      for job in modulePrebuildJobs {
+        try Self.printJob(job, resolver: try ArgsResolver(),
+                          forceResponseFiles: forceResponseFiles)
       }
     }
 
@@ -216,6 +210,18 @@ extension Driver {
     return jobs
   }
 
+  /// Prescan the source files to produce a module dependency graph and turn it into a set
+  /// of jobs required to build all dependencies.
+  public mutating func generateExplicitModuleBuildJobs() throws -> [Job] {
+    let moduleDependencyGraph = try computeModuleDependencyGraph()
+    if let dependencyGraph = moduleDependencyGraph {
+      let modulePrebuildJobs =
+            try planExplicitModuleDependenciesCompile(dependencyGraph: dependencyGraph)
+      return modulePrebuildJobs
+    }
+    return []
+  }
+
   /// Create a job if needed for simple requests that can be immediately
   /// forwarded to the frontend.
   public mutating func immediateForwardingJob() throws -> Job? {

TestInputs/ExplicitModuleBuilds/CHeaders/A.h

@@ -0,0 +1 @@
+void funcA(void);

TestInputs/ExplicitModuleBuilds/CHeaders/B.h

@@ -0,0 +1,4 @@
+#include <A.h>
+
+void funcB(void);
+

TestInputs/ExplicitModuleBuilds/CHeaders/Bridging.h

@@ -0,0 +1,3 @@
+#include "BridgingOther.h"
+
+int bridging_other(void);

TestInputs/ExplicitModuleBuilds/CHeaders/BridgingOther.h

@@ -0,0 +1,3 @@
+#include "F.h"
+
+int bridging_other(void);

TestInputs/ExplicitModuleBuilds/CHeaders/C.h

@@ -0,0 +1,3 @@
+#include <B.h>
+
+void funcC(void);

TestInputs/ExplicitModuleBuilds/CHeaders/D.h

@@ -0,0 +1 @@
+void funcD(void);

TestInputs/ExplicitModuleBuilds/CHeaders/F.h

@@ -0,0 +1 @@
+void funcF(void);

TestInputs/ExplicitModuleBuilds/CHeaders/G.h

@@ -0,0 +1 @@
+void funcG(void);

TestInputs/ExplicitModuleBuilds/CHeaders/module.modulemap

@@ -0,0 +1,29 @@
+module A {
+  header "A.h"
+  export *
+}
+
+module B {
+  header "B.h"
+  export *
+}
+
+module C {
+  header "C.h"
+  export *
+}
+
+module D {
+  header "D.h"
+  export *
+}
+
+module F {
+  header "F.h"
+  export *
+}
+
+module G {
+  header "G.h"
+  export *
+}