[Serialization] Remark on transitive dependencies

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -1031,6 +1031,11 @@ REMARK(module_loaded,none,
        "%select{| (overlay for a clang dependency)}1"
        "; source: '%2', loaded: '%3'",
        (Identifier, unsigned, StringRef, StringRef))
+
+REMARK(transitive_dependency_behavior,none,
+       "%1 has %select{a required|an optional|an ignored}2 "
+       "transitive dependency on '%0'",
+       (StringRef, Identifier, unsigned))
 
 REMARK(explicit_interface_build_skipped,none,
        "Skipped rebuilding module at %0 - up-to-date",

lib/Serialization/ModuleFile.cpp

@@ -17,6 +17,7 @@
 #include "ModuleFormat.h"
 #include "swift/Serialization/SerializationOptions.h"
 #include "swift/Subsystems.h"
+#include "swift/AST/DiagnosticsSema.h"
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/ASTMangler.h"
 #include "swift/AST/GenericSignature.h"
@@ -197,6 +198,14 @@ Status ModuleFile::associateWithFileContext(FileUnit *file, SourceLoc diagLoc,
     ModuleLoadingBehavior transitiveBehavior =
       getTransitiveLoadingBehavior(dependency);
 
+    if (ctx.LangOpts.EnableModuleLoadingRemarks) {
+      ctx.Diags.diagnose(diagLoc,
+                         diag::transitive_dependency_behavior,
+                         dependency.Core.getPrettyPrintedPath(),
+                         M->getName(),
+                         unsigned(transitiveBehavior));
+    }
+
     // Skip this dependency?
     if (transitiveBehavior == ModuleLoadingBehavior::Ignored)
       continue;

test/ModuleInterface/loading-remarks.swift

@@ -49,8 +49,10 @@ import SwiftDependency
 import SwiftNonResilientDependency
 import DirectMixedDependency
 
+// CHECK: remark: 'Swift' has a required transitive dependency on 'SwiftShims'
 // CHECK: remark: loaded module 'SwiftShims'; source: '{{.*}}module.modulemap', loaded: '{{.*}}SwiftShims-{{.*}}.pcm'
 // CHECK: remark: loaded module 'Swift'; source: '{{.*}}Swift.swiftmodule{{.*}}.swiftinterface', loaded: '{{.*}}Swift.swiftmodule{{.*}}.swiftmodule'
+// CHECK: remark: 'SwiftDependency' has a required transitive dependency on 'Swift'
 // CHECK: remark: loaded module 'SwiftDependency'; source: '{{.*}}SwiftDependency.swiftinterface', loaded: '{{.*}}SwiftDependency-{{.*}}.swiftmodule'
 // CHECK: remark: loaded module 'SwiftNonResilientDependency'; source: '{{.*}}SwiftNonResilientDependency.swiftmodule', loaded: '{{.*}}SwiftNonResilientDependency.swiftmodule'
 // CHECK: remark: loaded module 'IndirectMixedDependency' (overlay for a clang dependency); source: '{{.*}}IndirectMixedDependency.swiftinterface', loaded: '{{.*}}IndirectMixedDependency-{{.*}}.swiftmodule'

test/Serialization/package-dependencies.swift

@@ -25,13 +25,13 @@ package import PackageDep
 // RUN:   -package-name MyPackage -I %t \
 // RUN:   -enable-experimental-feature AccessLevelOnImport \
 // RUN:   -Rmodule-loading 2>&1 | %FileCheck -check-prefix=VISIBLE-PACKAGE-DEP %s
-// VISIBLE-PACKAGE-DEP: source: '{{.*}}PackageDep.swiftmodule'
+// VISIBLE-PACKAGE-DEP: loaded module 'PackageDep'
 
 // RUN: %target-swift-frontend -typecheck %t/ResilientClient.swift \
 // RUN:   -package-name NotMyPackage -I %t \
 // RUN:   -enable-experimental-feature AccessLevelOnImport \
 // RUN:   -Rmodule-loading 2>&1 | %FileCheck -check-prefix=HIDDEN-PACKAGE-DEP %s
-// HIDDEN-PACKAGE-DEP-NOT: PackageDep
+// HIDDEN-PACKAGE-DEP-NOT: loaded module 'PackageDep'
 
 //--- ResilientClient.swift
 import ResilientDep