Warning for framework include violation from Headers to PrivateHeaders

Framework vendors usually layout their framework headers in the
following way:

Foo.framework/Headers -> "public" headers
Foo.framework/PrivateHeader -> "private" headers

Since both headers in both directories can be found with #import
<Foo/some-header.h>, it's easy to make mistakes and include headers in
Foo.framework/PrivateHeader from headers in Foo.framework/Headers, which
usually configures a layering violation on Darwin ecosystems. One of the
problem this causes is dep cycles when modules are used, since it's very
common for "private" modules to include from the "public" ones; adding
an edge the other way around will trigger cycles.

Add a warning to catch those cases such that:

./A.framework/Headers/A.h:1:10: warning: public framework header includes private framework header 'A/APriv.h'
#include <A/APriv.h>
         ^

rdar://problem/38712182

llvm-svn: 335542

Author: bcardosolopes

clang/include/clang/Basic/DiagnosticGroups.td

@@ -32,6 +32,8 @@ def Availability : DiagGroup<"availability">;
 def Section : DiagGroup<"section">;
 def AutoImport : DiagGroup<"auto-import">;
 def FrameworkHdrQuotedInclude : DiagGroup<"quoted-include-in-framework-header">;
+def FrameworkIncludePrivateFromPublic :
+  DiagGroup<"framework-include-private-from-public">;
 def CXX14BinaryLiteral : DiagGroup<"c++14-binary-literal">;
 def CXXPre14CompatBinaryLiteral : DiagGroup<"c++98-c++11-compat-binary-literal">;
 def GNUBinaryLiteral : DiagGroup<"gnu-binary-literal">;

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -718,6 +718,9 @@ def warn_quoted_include_in_framework_header : Warning<
   "double-quoted include \"%0\" in framework header, "
   "expected angle-bracketed instead"
   >, InGroup<FrameworkHdrQuotedInclude>, DefaultIgnore;
+def warn_framework_include_private_from_public : Warning<
+  "public framework header includes private framework header '%0'"
+  >, InGroup<FrameworkIncludePrivateFromPublic>;
 
 def warn_auto_module_import : Warning<
   "treating #%select{include|import|include_next|__include_macros}0 as an "

clang/lib/Lex/HeaderSearch.cpp

@@ -621,11 +621,12 @@ static const char *copyString(StringRef Str, llvm::BumpPtrAllocator &Alloc) {
   return CopyStr;
 }
 
-static bool isFrameworkStylePath(StringRef Path,
+static bool isFrameworkStylePath(StringRef Path, bool &IsPrivateHeader,
                                  SmallVectorImpl<char> &FrameworkName) {
   using namespace llvm::sys;
   path::const_iterator I = path::begin(Path);
   path::const_iterator E = path::end(Path);
+  IsPrivateHeader = false;
 
   // Detect different types of framework style paths:
   //
@@ -637,12 +638,16 @@ static bool isFrameworkStylePath(StringRef Path,
   // and some other variations among these lines.
   int FoundComp = 0;
   while (I != E) {
+    if (*I == "Headers")
+      ++FoundComp;
     if (I->endswith(".framework")) {
       FrameworkName.append(I->begin(), I->end());
       ++FoundComp;
     }
-    if (*I == "Headers" || *I == "PrivateHeaders")
+    if (*I == "PrivateHeaders") {
       ++FoundComp;
+      IsPrivateHeader = true;
+    }
     ++I;
   }
 
@@ -654,11 +659,13 @@ diagnoseFrameworkInclude(DiagnosticsEngine &Diags, SourceLocation IncludeLoc,
                          StringRef Includer, StringRef IncludeFilename,
                          const FileEntry *IncludeFE, bool isAngled = false,
                          bool FoundByHeaderMap = false) {
+  bool IsIncluderPrivateHeader = false;
   SmallString<128> FromFramework, ToFramework;
-  if (!isFrameworkStylePath(Includer, FromFramework))
+  if (!isFrameworkStylePath(Includer, IsIncluderPrivateHeader, FromFramework))
     return;
-  bool IsIncludeeInFramework =
-      isFrameworkStylePath(IncludeFE->getName(), ToFramework);
+  bool IsIncludeePrivateHeader = false;
+  bool IsIncludeeInFramework = isFrameworkStylePath(
+      IncludeFE->getName(), IsIncludeePrivateHeader, ToFramework);
 
   if (!isAngled && !FoundByHeaderMap) {
     SmallString<128> NewInclude("<");
@@ -672,6 +679,14 @@ diagnoseFrameworkInclude(DiagnosticsEngine &Diags, SourceLocation IncludeLoc,
         << IncludeFilename
         << FixItHint::CreateReplacement(IncludeLoc, NewInclude);
   }
+
+  // Headers in Foo.framework/Headers should not include headers
+  // from Foo.framework/PrivateHeaders, since this violates public/private
+  // API boundaries and can cause modular dependency cycles.
+  if (!IsIncluderPrivateHeader && IsIncludeeInFramework &&
+      IsIncludeePrivateHeader && FromFramework == ToFramework)
+    Diags.Report(IncludeLoc, diag::warn_framework_include_private_from_public)
+        << IncludeFilename;
 }
 
 /// LookupFile - Given a "foo" or \<foo> reference, look up the indicated file,

clang/test/Modules/Inputs/framework-public-includes-private/A.framework/Headers/A.h

@@ -0,0 +1,4 @@
+#include <A/APriv.h>
+#include "APriv2.h"
+#include <Z/Z.h>
+int foo();

clang/test/Modules/Inputs/framework-public-includes-private/A.framework/Modules/module.modulemap

@@ -0,0 +1,4 @@
+// framework-public-includes-private/A.framework/Modules/module.modulemap
+framework module A {
+  header "A.h"
+}

clang/test/Modules/Inputs/framework-public-includes-private/A.framework/Modules/module.private.modulemap

@@ -0,0 +1,4 @@
+// framework-public-includes-private/A.framework/Modules/module.private.modulemap
+framework module A_Private {
+  header "APriv.h"
+}

clang/test/Modules/Inputs/framework-public-includes-private/A.framework/PrivateHeaders/APriv.h

@@ -0,0 +1 @@
+// framework-public-includes-private/A.framework/PrivateHeaders/APriv.h

clang/test/Modules/Inputs/framework-public-includes-private/A.framework/PrivateHeaders/APriv2.h

@@ -0,0 +1 @@
+// framework-public-includes-private/A.framework/PrivateHeaders/APriv2.h

clang/test/Modules/Inputs/framework-public-includes-private/a.hmap.json

@@ -0,0 +1,8 @@
+
+{
+  "mappings" :
+    {
+     "A.h" : "A/A.h",
+     "APriv2.h" : "A/APriv2.h"
+    }
+}

clang/test/Modules/Inputs/framework-public-includes-private/flat-header-path/Z.h

@@ -0,0 +1,2 @@
+// framework-public-includes-private/flat-header-path/Z.h
+#import "ZPriv.h"