Introduce infrastructure to dump generated source buffers into temporary files

Author: DougGregor

include/swift/Basic/SourceManager.h

@@ -72,6 +72,10 @@ class GeneratedSourceInfo {
 
   /// The custom attribute for an attached macro.
   CustomAttr *attachedMacroCustomAttr = nullptr;
+
+  /// The name of the source file on disk that was created to hold the
+  /// contents of this file for external clients.
+  StringRef onDiskBufferCopyFileName = StringRef();
 };
 
 /// This class manages and owns source buffers.
@@ -253,11 +257,18 @@ class SourceManager {
   ///
   /// \p BufferID must be a valid buffer ID.
   ///
+  /// \p ForceGeneratedSourceToDisk can be set to true to create a temporary
+  /// file on-disk for buffers containing generated source code, returning the
+  /// name of that temporary file.
+  ///
   /// This should not be used for displaying information about the \e contents
   /// of a buffer, since lines within the buffer may be marked as coming from
   /// other files using \c #sourceLocation. Use #getDisplayNameForLoc instead
   /// in that case.
-  StringRef getIdentifierForBuffer(unsigned BufferID) const;
+  StringRef getIdentifierForBuffer(
+      unsigned BufferID,
+      bool ForceGeneratedSourceToDisk = false
+  ) const;
 
   /// Returns a SourceRange covering the entire specified buffer.
   ///
@@ -289,10 +300,15 @@ class SourceManager {
   /// Returns a buffer identifier suitable for display to the user containing
   /// the given source location.
   ///
+  /// \p ForceGeneratedSourceToDisk can be set to true to create a temporary
+  /// file on-disk for buffers containing generated source code, returning the
+  /// name of that temporary file.
+  ///
   /// This respects \c #sourceLocation directives and the 'use-external-names'
   /// directive in VFS overlay files. If you need an on-disk file name, use
   /// #getIdentifierForBuffer instead.
-  StringRef getDisplayNameForLoc(SourceLoc Loc) const;
+  StringRef getDisplayNameForLoc(
+      SourceLoc Loc, bool ForceGeneratedSourceToDisk = false) const;
 
   /// Returns the line and column represented by the given source location.
   ///

lib/Basic/SourceLoc.cpp

@@ -12,9 +12,11 @@
 
 #include "swift/Basic/SourceLoc.h"
 #include "swift/Basic/SourceManager.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Signals.h"
 
 using namespace swift;
 
@@ -43,13 +45,14 @@ SourceLoc SourceManager::getIDEInspectionTargetLoc() const {
       .getAdvancedLoc(IDEInspectionTargetOffset);
 }
 
-StringRef SourceManager::getDisplayNameForLoc(SourceLoc Loc) const {
+StringRef SourceManager::getDisplayNameForLoc(SourceLoc Loc, bool ForceGeneratedSourceToDisk) const {
   // Respect #line first
   if (auto VFile = getVirtualFile(Loc))
     return VFile->Name;
 
   // Next, try the stat cache
-  auto Ident = getIdentifierForBuffer(findBufferContainingLoc(Loc));
+  auto Ident = getIdentifierForBuffer(
+      findBufferContainingLoc(Loc), ForceGeneratedSourceToDisk);
   auto found = StatusCache.find(Ident);
   if (found != StatusCache.end()) {
     return found->second.getName();
@@ -184,9 +187,53 @@ SourceManager::getIDForBufferIdentifier(StringRef BufIdentifier) const {
   return It->second;
 }
 
-StringRef SourceManager::getIdentifierForBuffer(unsigned bufferID) const {
+/// Dump the contents of the given memory buffer to a file, returning the
+/// name of that file (when successful) and \c None otherwise.
+static Optional<std::string>
+dumpBufferToFile(const llvm::MemoryBuffer *buffer) {
+  // Create file in the system temporary directory.
+  SmallString<128> tempFileModel;
+  llvm::sys::path::system_temp_directory(true, tempFileModel);
+  llvm::sys::path::append(
+      tempFileModel, "swift-generated-sources-%%%%%%.swift");
+
+  // Open up a unique file.
+  int tempFD = 0;
+  SmallString<128> tempFileName;
+  if (llvm::sys::fs::createUniqueFile(tempFileModel, tempFD, tempFileName))
+    return None;
+
+  // Dump the contents there.
+  llvm::raw_fd_ostream out(tempFD, true);
+  out << buffer->getBuffer();
+  out.flush();
+
+  llvm::sys::DontRemoveFileOnSignal(tempFileName);
+  return tempFileName.str().str();
+}
+
+StringRef SourceManager::getIdentifierForBuffer(
+    unsigned bufferID, bool ForceGeneratedSourceToDisk
+) const {
   auto *buffer = LLVMSourceMgr.getMemoryBuffer(bufferID);
   assert(buffer && "invalid buffer ID");
+
+  // If this is generated source code, and we're supposed to force it to disk
+  // so external clients can see it, do so now.
+  if (ForceGeneratedSourceToDisk) {
+    if (auto generatedInfo = getGeneratedSourceInfo(bufferID)) {
+      if (generatedInfo->onDiskBufferCopyFileName.empty()) {
+        if (auto newFileNameOpt = dumpBufferToFile(buffer)) {
+          generatedInfo->onDiskBufferCopyFileName =
+              strdup(newFileNameOpt->c_str());
+        }
+      }
+
+      if (!generatedInfo->onDiskBufferCopyFileName.empty())
+        return generatedInfo->onDiskBufferCopyFileName;
+    }
+  }
+
   return buffer->getBufferIdentifier();
 }