[libclang] Add C interface for querying against ModuleDeps

Previously the callback used for getting the output path of pcm's took
in the ModuleID, which represents the name & context hash. Now that
there are more attributes to determine the output path, like the
attribute `isInStableDirectories`. To support this case,
allow clients to override the signature of the callback to pass along a reference to the whole
`ModuleDep` object instead.

Additionally, this patch:

* Makes calls that unwrap `CXDepGraphModule` const correct.
* Provides an API to query whether a module comes from
  stable directories.

(cherry picked from commit fa17ed7)

Author: cyndyishida

clang/include/clang-c/Dependencies.h

@@ -417,6 +417,27 @@ typedef struct CXOpaqueDepGraphTUCommand *CXDepGraphTUCommand;
 typedef struct CXOpaqueDependencyScannerWorkerScanSettings
     *CXDependencyScannerWorkerScanSettings;
 
+/**
+ * A callback that is called to determine the paths of output files for each
+ * module dependency. The ModuleFile (pcm) path mapping is mandatory.
+ *
+ * \param Context the MLOContext that was passed to
+ *         \c clang_experimental_DependencyScannerWorker_getFileDependencies_vX.
+ * \param CXDepMod the ModuleDep that represents the dependent module.
+ * \param OutputKind the kind of module output to lookup.
+ * \param[out] Output the output path(s) or name, whose total size must be <=
+ *                    \p MaxLen. In the case of multiple outputs of the same
+ *                    kind, this can be a null-separated list.
+ * \param MaxLen the maximum size of Output.
+ *
+ * \returns the actual length of Output. If the return value is > \p MaxLen,
+ *          the callback will be repeated with a larger buffer.
+ */
+typedef size_t CXModuleLookupOutputCallback_v2(void *Context,
+                                               CXDepGraphModule CXDepMod,
+                                               CXOutputKind OutputKind,
+                                               char *Output, size_t MaxLen);
+
 /**
  * Creates a set of settings for
  * \c clang_experimental_DependencyScannerWorker_getDepGraph action.
@@ -447,6 +468,23 @@ clang_experimental_DependencyScannerWorkerScanSettings_create(
     const char *WorkingDirectory, void *MLOContext,
     CXModuleLookupOutputCallback *MLO);
 
+/**
+ * Override the ModuleLookupOutputCallback with \c
+ * CXModuleLookupOutputCallback_v2 in the scanner settings for queries of module
+ * dependencies. This is required for handling output paths of modules that
+ * depend on attributes encoded in
+ * \c CXDepGraphModule.
+ *
+ * \param Settings object created via
+ *     \c clang_experimental_DependencyScannerWorkerScanSettings_create.
+ * \param MLO a callback that is called to determine the paths of output files
+ *            for each module dependency. This may receive the same module on
+ *            different workers.
+ */
+CINDEX_LINKAGE void
+clang_experimental_DependencyScannerWorkerScanSettings_setModuleLookupCallback(
+    CXDependencyScannerWorkerScanSettings, CXModuleLookupOutputCallback_v2 *);
+
 /**
  * Dispose of a \c CXDependencyScannerWorkerScanSettings object.
  */
@@ -565,6 +603,13 @@ CINDEX_LINKAGE CXCStringArray
 CINDEX_LINKAGE CXCStringArray
     clang_experimental_DepGraphModule_getModuleDeps(CXDepGraphModule);
 
+/**
+ * \returns whether the provided module is comprised of
+ * inputs that resolve into stable directories.
+ */
+CINDEX_LINKAGE bool
+    clang_experimental_DepGraphModule_isInStableDirs(CXDepGraphModule);
+
 /**
  * \returns the canonical command line to build this module.
  *

clang/test/ClangScanDeps/stable-dirs-c-api.c

@@ -0,0 +1,25 @@
+// REQUIRES: shell
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// RUN: c-index-test core -scan-deps -working-dir %S -- %clang \
+// RUN:   -c %t/client.c -fmodules -fmodules-cache-path=%t/module-cache \
+// RUN:   -isysroot %t/Sysroot -I %t/Sysroot/usr/include 2>&1 | FileCheck %s \
+// RUN:   -implicit-check-not error: -implicit-check-not=warning:
+
+//--- Sysroot/usr/include/A/module.modulemap
+module A {
+  umbrella "."
+}
+
+//--- Sysroot/usr/include/A/A.h
+typedef int A_t;
+
+//--- client.c
+#include <A/A.h>
+
+
+// CHECK:       module: 
+// CHECK-NEXT:    name: A
+// CHECK:         is-in-stable-directories: 1 
+

clang/tools/c-index-test/core_main.cpp

@@ -815,6 +815,8 @@ static int scanDeps(ArrayRef<const char *> Args, std::string WorkingDirectory,
       const char *ContextHash =
           clang_experimental_DepGraphModule_getContextHash(Mod);
       int CwdIgnored = clang_experimental_DepGraphModule_isCWDIgnored(Mod);
+      bool IsInStableDir =
+          clang_experimental_DepGraphModule_isInStableDirs(Mod);
       const char *ModuleMapPath =
           clang_experimental_DepGraphModule_getModuleMapPath(Mod);
       const char *ModuleIncludeTreeID =
@@ -835,6 +837,9 @@ static int scanDeps(ArrayRef<const char *> Args, std::string WorkingDirectory,
                    << "    cwd-ignored: " << CwdIgnored << "\n"
                    << "    module-map-path: "
                    << (ModuleMapPath ? ModuleMapPath : "<none>") << "\n";
+      if (IsInStableDir)
+        llvm::outs() << "    is-in-stable-directories: " << IsInStableDir
+                     << "\n";
       if (ModuleIncludeTreeID)
         llvm::outs() << "    include-tree-id: " << ModuleIncludeTreeID << "\n";
       if (ModuleCacheKey)

clang/tools/libclang/CDependencies.cpp

@@ -23,6 +23,7 @@
 #include "clang/Tooling/DependencyScanning/DependencyScanningService.h"
 #include "clang/Tooling/DependencyScanning/DependencyScanningTool.h"
 #include "clang/Tooling/DependencyScanning/DependencyScanningWorker.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/CAS/CASProvidingFileSystem.h"
 #include "llvm/CAS/CachingOnDiskFileSystem.h"
 #include "llvm/Support/Process.h"
@@ -332,14 +333,18 @@ static CXErrorCode getFileDependencies(CXDependencyScannerWorker W, int argc,
 namespace {
 class OutputLookup {
 public:
-  OutputLookup(void *MLOContext, CXModuleLookupOutputCallback *MLO)
+  OutputLookup(void *MLOContext, std::variant<CXModuleLookupOutputCallback *,
+                                              CXModuleLookupOutputCallback_v2 *>
+                                     MLO)
       : MLOContext(MLOContext), MLO(MLO) {}
   std::string lookupModuleOutput(const ModuleDeps &MD, ModuleOutputKind MOK);
 
 private:
   llvm::DenseMap<ModuleID, std::string> PCMPaths;
   void *MLOContext;
-  CXModuleLookupOutputCallback *MLO;
+  std::variant<CXModuleLookupOutputCallback *,
+               CXModuleLookupOutputCallback_v2 *>
+      MLO;
 };
 } // end anonymous namespace
 
@@ -422,7 +427,9 @@ struct DependencyScannerWorkerScanSettings {
   const char *ModuleName;
   const char *WorkingDirectory;
   void *MLOContext;
-  CXModuleLookupOutputCallback *MLO;
+  std::variant<CXModuleLookupOutputCallback *,
+               CXModuleLookupOutputCallback_v2 *>
+      MLO;
 };
 
 struct CStringsManager {
@@ -482,7 +489,7 @@ struct DependencyGraph {
 };
 
 struct DependencyGraphModule {
-  ModuleDeps *ModDeps;
+  const ModuleDeps *ModDeps;
   CStringsManager StrMgr{};
 };
 
@@ -523,7 +530,9 @@ enum CXErrorCode clang_experimental_DependencyScannerWorker_getDepGraph(
   const char *ModuleName = Settings.ModuleName;
   const char *WorkingDirectory = Settings.WorkingDirectory;
   void *MLOContext = Settings.MLOContext;
-  CXModuleLookupOutputCallback *MLO = Settings.MLO;
+  std::variant<CXModuleLookupOutputCallback *,
+               CXModuleLookupOutputCallback_v2 *>
+      MLO = Settings.MLO;
 
   OutputLookup OL(MLOContext, MLO);
   auto LookupOutputs = [&](const ModuleDeps &MD, ModuleOutputKind MOK) {
@@ -582,60 +591,65 @@ void clang_experimental_DepGraphModule_dispose(CXDepGraphModule CXDepMod) {
 
 const char *
 clang_experimental_DepGraphModule_getName(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   return ModDeps.ID.ModuleName.c_str();
 }
 
 const char *
 clang_experimental_DepGraphModule_getContextHash(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   return ModDeps.ID.ContextHash.c_str();
 }
 
 const char *
 clang_experimental_DepGraphModule_getModuleMapPath(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   if (ModDeps.ClangModuleMapFile.empty())
     return nullptr;
   return ModDeps.ClangModuleMapFile.c_str();
 }
 
 CXCStringArray
 clang_experimental_DepGraphModule_getFileDeps(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   std::vector<std::string> FileDeps;
   ModDeps.forEachFileDep([&](StringRef File) { FileDeps.emplace_back(File); });
   return unwrap(CXDepMod)->StrMgr.createCStringsOwned(std::move(FileDeps));
 }
 
 CXCStringArray
 clang_experimental_DepGraphModule_getModuleDeps(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   std::vector<std::string> Modules;
   Modules.reserve(ModDeps.ClangModuleDeps.size());
   for (const ModuleID &MID : ModDeps.ClangModuleDeps)
     Modules.push_back(MID.ModuleName + ":" + MID.ContextHash);
   return unwrap(CXDepMod)->StrMgr.createCStringsOwned(std::move(Modules));
 }
 
+bool clang_experimental_DepGraphModule_isInStableDirs(
+    CXDepGraphModule CXDepMod) {
+  return unwrap(CXDepMod)->ModDeps->IsInStableDirectories;
+}
+
 CXCStringArray
 clang_experimental_DepGraphModule_getBuildArguments(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   return unwrap(CXDepMod)->StrMgr.createCStringsRef(
       ModDeps.getBuildArguments());
 }
 
 const char *
 clang_experimental_DepGraphModule_getIncludeTreeID(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   if (ModDeps.IncludeTreeID)
     return ModDeps.IncludeTreeID->c_str();
   return nullptr;
 }
 
 const char *
 clang_experimental_DepGraphModule_getCacheKey(CXDepGraphModule CXDepMod) {
-  ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
+  const ModuleDeps &ModDeps = *unwrap(CXDepMod)->ModDeps;
   if (ModDeps.ModuleCacheKey)
     return ModDeps.ModuleCacheKey->c_str();
   return nullptr;
@@ -706,22 +720,46 @@ const char *clang_experimental_DepGraph_getTUContextHash(CXDepGraph Graph) {
   return TUDeps.ID.ContextHash.c_str();
 }
 
+void clang_experimental_DependencyScannerWorkerScanSettings_setModuleLookupCallback(
+    CXDependencyScannerWorkerScanSettings CXSettings,
+    CXModuleLookupOutputCallback_v2 *MLO) {
+  DependencyScannerWorkerScanSettings &Settings = *unwrap(CXSettings);
+  Settings.MLO = MLO;
+}
+
 CXDiagnosticSet clang_experimental_DepGraph_getDiagnostics(CXDepGraph Graph) {
   return unwrap(Graph)->getDiagnosticSet();
 }
 
-static std::string lookupModuleOutput(const ModuleDeps &MD,
-                                      ModuleOutputKind MOK, void *MLOContext,
-                                      CXModuleLookupOutputCallback *MLO) {
+static std::string
+lookupModuleOutput(const ModuleDeps &MD, ModuleOutputKind MOK, void *MLOContext,
+                   std::variant<CXModuleLookupOutputCallback *,
+                                CXModuleLookupOutputCallback_v2 *>
+                       MLO) {
   SmallVector<char, 256> Buffer(256);
-  size_t Len =
-      MLO(MLOContext, MD.ID.ModuleName.c_str(), MD.ID.ContextHash.c_str(),
-          wrap(MOK), Buffer.data(), Buffer.size());
+  auto GetLengthFromOutputCallback = [&]() {
+    return std::visit(llvm::makeVisitor(
+                          [&](CXModuleLookupOutputCallback *) -> size_t {
+                            return std::get<CXModuleLookupOutputCallback *>(
+                                MLO)(MLOContext, MD.ID.ModuleName.c_str(),
+                                     MD.ID.ContextHash.c_str(), wrap(MOK),
+                                     Buffer.data(), Buffer.size());
+                          },
+                          [&](CXModuleLookupOutputCallback_v2 *) -> size_t {
+                            return std::get<CXModuleLookupOutputCallback_v2 *>(
+                                MLO)(MLOContext,
+                                     wrap(new DependencyGraphModule{&MD}),
+                                     wrap(MOK), Buffer.data(), Buffer.size());
+                          }),
+                      MLO);
+  };
+
+  size_t Len = GetLengthFromOutputCallback();
   if (Len > Buffer.size()) {
     Buffer.resize(Len);
-    Len = MLO(MLOContext, MD.ID.ModuleName.c_str(), MD.ID.ContextHash.c_str(),
-              wrap(MOK), Buffer.data(), Buffer.size());
+    Len = GetLengthFromOutputCallback();
   }
+
   return std::string(Buffer.begin(), Len);
 }
 

clang/tools/libclang/libclang.map

@@ -574,6 +574,7 @@ LLVM_21 {
   global:
     clang_experimental_DependencyScannerServiceOptions_setCWDOptimization;
     clang_experimental_DepGraphModule_isCWDIgnored;
+    clang_experimental_DepGraphModule_isInStableDirs; 
 };
 
 # Example of how to add a new symbol version entry.  If you do add a new symbol