1 files changed, 40 insertions, 7 deletions

diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index f3c337a..0ae9fa60 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -3181,6 +3181,8 @@ const char *StyleOptionHelpDescription =
     ".clang-format file located in one of the parent\n"
     "directories of the source file (or current\n"
     "directory for stdin).\n"
+    "Use -style=file:<format_file_path> to explicitly specify"
+    "the configuration file.\n"
     "Use -style=\"{key: value, ...}\" to set specific\n"
     "parameters, e.g.:\n"
     "  -style=\"{BasedOnStyle: llvm, IndentWidth: 8}\"";
@@ -3233,6 +3235,18 @@ const char *DefaultFormatStyle = "file";
 
 const char *DefaultFallbackStyle = "LLVM";
 
+llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+loadAndParseConfigFile(StringRef ConfigFile, llvm::vfs::FileSystem *FS,
+                       FormatStyle *Style, bool AllowUnknownOptions) {
+  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
+      FS->getBufferForFile(ConfigFile.str());
+  if (auto EC = Text.getError())
+    return EC;
+  if (auto EC = parseConfiguration(*Text.get(), Style, AllowUnknownOptions))
+    return EC;
+  return Text;
+}
+
 llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
                                      StringRef FallbackStyleName,
                                      StringRef Code, llvm::vfs::FileSystem *FS,
@@ -3263,6 +3277,28 @@ llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
       return Style;
   }
 
+  // User provided clang-format file using -style=file:path/to/format/file.
+  if (!Style.InheritsParentConfig &&
+      StyleName.startswith_insensitive("file:")) {
+    auto ConfigFile = StyleName.substr(5);
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
+        loadAndParseConfigFile(ConfigFile, FS, &Style, AllowUnknownOptions);
+    if (auto EC = Text.getError())
+      return make_string_error("Error reading " + ConfigFile + ": " +
+                               EC.message());
+
+    LLVM_DEBUG(llvm::dbgs()
+               << "Using configuration file " << ConfigFile << "\n");
+
+    if (!Style.InheritsParentConfig)
+      return Style;
+
+    // Search for parent configs starting from the parent directory of
+    // ConfigFile.
+    FileName = ConfigFile;
+    ChildFormatTextToApply.emplace_back(std::move(*Text));
+  }
+
   // If the style inherits the parent configuration it is a command line
   // configuration, which wants to inherit, so we have to skip the check of the
   // StyleName.
@@ -3318,19 +3354,16 @@ llvm::Expected<FormatStyle> getStyle(StringRef StyleName, StringRef FileName,
       if (Status &&
           (Status->getType() == llvm::sys::fs::file_type::regular_file)) {
         llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
-            FS->getBufferForFile(ConfigFile.str());
-        if (std::error_code EC = Text.getError())
-          return make_string_error(EC.message());
-        if (std::error_code ec =
-                parseConfiguration(*Text.get(), &Style, AllowUnknownOptions)) {
-          if (ec == ParseError::Unsuitable) {
+            loadAndParseConfigFile(ConfigFile, FS, &Style, AllowUnknownOptions);
+        if (auto EC = Text.getError()) {
+          if (EC == ParseError::Unsuitable) {
             if (!UnsuitableConfigFiles.empty())
               UnsuitableConfigFiles.append(", ");
             UnsuitableConfigFiles.append(ConfigFile);
             continue;
           }
           return make_string_error("Error reading " + ConfigFile + ": " +
-                                   ec.message());
+                                   EC.message());
         }
         LLVM_DEBUG(llvm::dbgs()
                    << "Using configuration file " << ConfigFile << "\n");