[CAS] Improve CAS ObjectStore initialization

Make `getDefaultOnDiskCASPath` return error types as the function can
fail (current fatal errors) on certain OS configurations.

Also deprecate the API that uses DefaultOnDiskStableID.

Author: cachemeifyoucan

clang/tools/driver/cc1depscan_main.cpp

@@ -833,7 +833,12 @@ void ScanServer::start(bool Exclusive, ArrayRef<const char *> CASArgs) {
       return;
     SmallString<64> LLVMCasStorage;
     SmallString<64> CASPath;
-    CASOpts.getResolvedCASPath(CASPath);
+    if (auto Err = CASOpts.getResolvedCASPath(CASPath)) {
+      // Failure to resolve a cas path for validation is ignored, because any
+      // error will be reported when attempting to open the cas.
+      llvm::consumeError(std::move(Err));
+      return;
+    }
     ExitOnErr(llvm::cas::validateOnDiskUnifiedCASDatabasesIfNeeded(
         CASPath, /*CheckHash=*/true,
         /*AllowRecovery=*/true,

llvm/include/llvm/CAS/CASConfiguration.h

@@ -49,9 +49,6 @@ class CASConfiguration {
     return !(LHS == RHS);
   }
 
-  // Get resolved CASPath.
-  void getResolvedCASPath(llvm::SmallVectorImpl<char> &Result) const;
-
   // Create CASDatabase from the CASConfiguration.
   llvm::Expected<std::pair<std::shared_ptr<llvm::cas::ObjectStore>,
                            std::shared_ptr<llvm::cas::ActionCache>>>
@@ -72,6 +69,9 @@ class CASConfiguration {
   createFromSearchConfigFile(
       StringRef Path,
       llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS = nullptr);
+
+  /// Get resolved CASPath.
+  Error getResolvedCASPath(llvm::SmallVectorImpl<char> &Result) const;
 };
 
 } // namespace llvm::cas

llvm/include/llvm/CAS/ObjectStore.h

@@ -358,27 +358,15 @@ std::unique_ptr<ObjectStore> createInMemoryCAS();
 bool isOnDiskCASEnabled();
 
 /// Gets or creates a persistent on-disk path at \p Path.
-///
-/// Deprecated: if \p Path resolves to \a getDefaultOnDiskCASStableID(),
-/// automatically opens \a getDefaultOnDiskCASPath() instead.
-///
-/// FIXME: Remove the special behaviour for getDefaultOnDiskCASStableID(). The
-/// client should handle this logic, if/when desired.
 Expected<std::unique_ptr<ObjectStore>> createOnDiskCAS(const Twine &Path);
 
 /// Set \p Path to a reasonable default on-disk path for a persistent CAS for
 /// the current user.
-void getDefaultOnDiskCASPath(SmallVectorImpl<char> &Path);
+Error getDefaultOnDiskCASPath(SmallVectorImpl<char> &Path);
 
 /// Get a reasonable default on-disk path for a persistent CAS for the current
 /// user.
-std::string getDefaultOnDiskCASPath();
-
-/// FIXME: Remove.
-void getDefaultOnDiskCASStableID(SmallVectorImpl<char> &Path);
-
-/// FIXME: Remove.
-std::string getDefaultOnDiskCASStableID();
+llvm::Expected<std::string> getDefaultOnDiskCASPath();
 
 /// Create ObjectStore from a string identifier.
 /// Currently the string identifier is using URL scheme with following supported

llvm/lib/CAS/CASConfiguration.cpp

@@ -15,13 +15,13 @@
 using namespace llvm;
 using namespace llvm::cas;
 
-void CASConfiguration::getResolvedCASPath(
+Error CASConfiguration::getResolvedCASPath(
     llvm::SmallVectorImpl<char> &Result) const {
-  if (CASPath == "auto") {
-    getDefaultOnDiskCASPath(Result);
-  } else {
-    Result.assign(CASPath.begin(), CASPath.end());
-  }
+  if (CASPath == "auto")
+    return getDefaultOnDiskCASPath(Result);
+
+  Result.assign(CASPath.begin(), CASPath.end());
+  return Error::success();
 }
 
 Expected<std::pair<std::shared_ptr<ObjectStore>, std::shared_ptr<ActionCache>>>
@@ -34,7 +34,8 @@ CASConfiguration::createDatabases() const {
   }
 
   SmallString<128> PathBuf;
-  getResolvedCASPath(PathBuf);
+  if (auto E = getResolvedCASPath(PathBuf))
+    return std::move(E);
 
   std::pair<std::unique_ptr<ObjectStore>, std::unique_ptr<ActionCache>> DBs;
   return createOnDiskUnifiedCASDatabases(PathBuf);

llvm/lib/CAS/ObjectStore.cpp

@@ -336,8 +336,12 @@ createPluginCASImpl(const Twine &URL) {
     }
   }
 
-  if (OnDiskPath.empty())
-    OnDiskPath = getDefaultOnDiskCASPath();
+  if (OnDiskPath.empty()) {
+    auto Path = getDefaultOnDiskCASPath();
+    if (!Path)
+      return Path.takeError();
+    OnDiskPath = *Path;
+  }
 
   std::pair<std::shared_ptr<ObjectStore>, std::shared_ptr<ActionCache>> CASDBs;
   if (Error E = createPluginCASDatabases(PluginPath, OnDiskPath, PluginArgs)
@@ -372,7 +376,8 @@ cas::createCASFromIdentifier(StringRef Path) {
   // FIXME: some current default behavior.
   SmallString<256> PathBuf;
   if (Path == "auto") {
-    getDefaultOnDiskCASPath(PathBuf);
+    if (auto E = getDefaultOnDiskCASPath(PathBuf))
+      return std::move(E);
     Path = PathBuf;
   }
 

llvm/lib/CAS/OnDiskCAS.cpp

@@ -206,10 +206,6 @@ Expected<std::unique_ptr<ObjectStore>> cas::createOnDiskCAS(const Twine &Path) {
   Path.toVector(AbsPath);
   sys::fs::make_absolute(AbsPath);
 
-  // FIXME: Remove this and update clients to do this logic.
-  if (AbsPath == getDefaultOnDiskCASStableID())
-    AbsPath = StringRef(getDefaultOnDiskCASPath());
-
   return OnDiskCAS::open(AbsPath);
 #else
   return createStringError(inconvertibleErrorCode(), "OnDiskCAS is disabled");
@@ -224,26 +220,16 @@ cas::builtin::createObjectStoreFromUnifiedOnDiskCache(
 
 static constexpr StringLiteral DefaultName = "cas";
 
-void cas::getDefaultOnDiskCASStableID(SmallVectorImpl<char> &Path) {
-  Path.assign(DefaultDirProxy.begin(), DefaultDirProxy.end());
-  llvm::sys::path::append(Path, DefaultDir, DefaultName);
-}
-
-std::string cas::getDefaultOnDiskCASStableID() {
-  SmallString<128> Path;
-  getDefaultOnDiskCASStableID(Path);
-  return Path.str().str();
-}
-
-void cas::getDefaultOnDiskCASPath(SmallVectorImpl<char> &Path) {
-  // FIXME: Should this return 'Error' instead of hard-failing?
+Error cas::getDefaultOnDiskCASPath(SmallVectorImpl<char> &Path) {
   if (!llvm::sys::path::cache_directory(Path))
-    report_fatal_error("cannot get default cache directory");
+    return createStringError("cache directory is not available");
   llvm::sys::path::append(Path, DefaultDir, DefaultName);
+  return Error::success();
 }
 
-std::string cas::getDefaultOnDiskCASPath() {
+Expected<std::string> cas::getDefaultOnDiskCASPath() {
   SmallString<128> Path;
-  getDefaultOnDiskCASPath(Path);
+  if (auto E = getDefaultOnDiskCASPath(Path))
+    return std::move(E);
   return Path.str().str();
 }

llvm/tools/llc/llc.cpp

@@ -346,10 +346,7 @@ static std::unique_ptr<ToolOutputFile> GetOutputStream(const char *TargetName,
 static std::shared_ptr<cas::ObjectStore> getCAS() {
   if (CASPath.empty())
     return cas::createInMemoryCAS();
-  auto MaybeCAS =
-      CASPath == "auto"
-          ? cas::createCASFromIdentifier(cas::getDefaultOnDiskCASPath())
-          : cas::createCASFromIdentifier(CASPath);
+  auto MaybeCAS = cas::createCASFromIdentifier(CASPath);
   if (MaybeCAS)
     return std::move(*MaybeCAS);
   reportError(toString(MaybeCAS.takeError()));