[modules] Handle modules with nonstandard names in module.private.modulemaps

Summary:
The module system supports accompanying a primary module (say Foo) with
an auxiliary "private" module (defined in an adjacent module.private.modulemap
file) that augments the primary module when associated private headers are
available. The feature is intended to be used to augment the primary
module with a submodule (say Foo.Private), however some users in the wild
are choosing to augment the primary module with an additional top-level module
with a "similar" name (in all cases so far: FooPrivate).

This "works" when a user of the module initially imports a private header,
such as '#import "Foo/something_private.h"' since the Foo import winds up
importing FooPrivate in passing. But if the import is subsequently recorded
in a PCH file, reloading the PCH will fail to validate because of a cross-check
that attempts to find the module.modulemap (or module.private.modulemap) using
HeaderSearch algorithm, applied to the "FooPrivate" name. Since it's stored in
Foo.framework/Modules, not FooPrivate.framework/Modules, the check fails and
the PCH is rejected.

This patch adds a compensatory workaround in the HeaderSearch algorithm
when searching (and failing to find) a module of the form FooPrivate: the
name used to derive filesystem paths is decoupled from the module name
being searched for, and if the initial search fails and the module is
named "FooPrivate", the filesystem search name is altered to remove the
"Private" suffix, and the algorithm is run a second time (still looking for
a module named FooPrivate, but looking in directories derived from Foo).

Accompanying this change is a new warning that triggers when a user loads
a module.private.modulemap that defines a top-level module with a different
name from the top-level module defined in its adjacent module.modulemap.

Reviewers: doug.gregor, manmanren, bruno

Subscribers: bruno, cfe-commits

Differential Revision: https://reviews.llvm.org/D27852

llvm-svn: 290219

2 files changed, 60 insertions, 4 deletions

diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 72e8b456822..b5228fc6c8c 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -194,16 +194,36 @@ Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch) {
   Module *Module = ModMap.findModule(ModuleName);
   if (Module || !AllowSearch || !HSOpts->ImplicitModuleMaps)
     return Module;
-  
+
+  StringRef SearchName = ModuleName;
+  Module = lookupModule(ModuleName, SearchName);
+
+  // The facility for "private modules" -- adjacent, optional module maps named
+  // module.private.modulemap that are supposed to define private submodules --
+  // is sometimes misused by frameworks that name their associated private
+  // module FooPrivate, rather than as a submodule named Foo.Private as
+  // intended. Here we compensate for such cases by looking in directories named
+  // Foo.framework, when we previously looked and failed to find a
+  // FooPrivate.framework.
+  if (!Module && SearchName.consume_back("Private"))
+    Module = lookupModule(ModuleName, SearchName);
+  return Module;
+}
+
+Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName) {
+  Module *Module = nullptr;
+
   // Look through the various header search paths to load any available module
   // maps, searching for a module map that describes this module.
   for (unsigned Idx = 0, N = SearchDirs.size(); Idx != N; ++Idx) {
     if (SearchDirs[Idx].isFramework()) {
-      // Search for or infer a module map for a framework.
+      // Search for or infer a module map for a framework. Here we use
+      // SearchName rather than ModuleName, to permit finding private modules
+      // named FooPrivate in buggy frameworks named Foo.
       SmallString<128> FrameworkDirName;
       FrameworkDirName += SearchDirs[Idx].getFrameworkDir()->getName();
-      llvm::sys::path::append(FrameworkDirName, ModuleName + ".framework");
-      if (const DirectoryEntry *FrameworkDir 
+      llvm::sys::path::append(FrameworkDirName, SearchName + ".framework");
+      if (const DirectoryEntry *FrameworkDir
             = FileMgr.getDirectory(FrameworkDirName)) {
         bool IsSystem
           = SearchDirs[Idx].getDirCharacteristic() != SrcMgr::C_User;
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index c1b7b33c31e..b7bba7ea9b8 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -1490,6 +1490,42 @@ void ModuleMapParser::parseModuleDecl() {
     ActiveModule->NoUndeclaredIncludes = true;
   ActiveModule->Directory = Directory;
 
+  if (!ActiveModule->Parent) {
+    StringRef MapFileName(ModuleMapFile->getName());
+    if (MapFileName.endswith("module.private.modulemap") ||
+        MapFileName.endswith("module_private.map")) {
+      // Adding a top-level module from a private modulemap is likely a
+      // user error; we check to see if there's another top-level module
+      // defined in the non-private map in the same dir, and if so emit a
+      // warning.
+      for (auto E = Map.module_begin(); E != Map.module_end(); ++E) {
+        auto const *M = E->getValue();
+        if (!M->Parent &&
+            M->Directory == ActiveModule->Directory &&
+            M->Name != ActiveModule->Name) {
+          Diags.Report(ActiveModule->DefinitionLoc,
+                       diag::warn_mmap_mismatched_top_level_private)
+            << ActiveModule->Name << M->Name;
+          // The pattern we're defending against here is typically due to
+          // a module named FooPrivate which is supposed to be a submodule
+          // called Foo.Private. Emit a fixit in that case.
+          auto D =
+            Diags.Report(ActiveModule->DefinitionLoc,
+                         diag::note_mmap_rename_top_level_private_as_submodule);
+          D << ActiveModule->Name << M->Name;
+          StringRef Bad(ActiveModule->Name);
+          if (Bad.consume_back("Private")) {
+            SmallString<128> Fixed = Bad;
+            Fixed.append(".Private");
+            D << FixItHint::CreateReplacement(ActiveModule->DefinitionLoc,
+                                              Fixed);
+          }
+          break;
+        }
+      }
+    }
+  }
+
   bool Done = false;
   do {
     switch (Tok.Kind) {