Support clang-format `file` and `--fallback-style` in slangd. (#2412)

Co-authored-by: Yong He <yhe@nvidia.com>

4 files changed, 63 insertions, 9 deletions

diff --git a/source/slang/slang-language-server-auto-format.cpp b/source/slang/slang-language-server-auto-format.cpp
index f7089bd4a..5bc9031ee 100644
--- a/source/slang/slang-language-server-auto-format.cpp
+++ b/source/slang/slang-language-server-auto-format.cpp
@@ -116,6 +116,42 @@ String parseXmlText(UnownedStringSlice text)
     return sb.ProduceString();
 }
 
+bool shouldUseFallbackStyle(const FormatOptions& options)
+{
+    if (!options.style.startsWith("file"))
+        return false;
+
+    String clangFormatFileName = ".clang-format";
+    bool standardFileName = true;
+    if (options.style.startsWith("file:"))
+    {
+        auto fileName = options.style.getUnownedSlice().tail(5);
+        if (fileName.startsWith("\""))
+            fileName = fileName.head(fileName.getLength() - 1).tail(1);
+        clangFormatFileName = fileName;
+        standardFileName = false;
+    }
+    auto path = options.fileName;
+    do
+    {
+        path = Path::getParentDirectory(path);
+        auto expectedFormatFileName = Path::combine(path, clangFormatFileName);
+        if (File::exists(expectedFormatFileName))
+        {
+            return false;
+        }
+        if (standardFileName)
+        {
+            expectedFormatFileName = Path::combine(path, "_clang_format");
+            if (File::exists(expectedFormatFileName))
+            {
+                return false;
+            }
+        }
+    } while (path.getLength());
+    return true;
+}
+
 List<Edit> formatSource(UnownedStringSlice text, Index lineStart, Index lineEnd, Index cursorOffset, const FormatOptions& options)
 {
     List<Edit> edits;
@@ -123,7 +159,9 @@ List<Edit> formatSource(UnownedStringSlice text, Index lineStart, Index lineEnd,
     String clangProcessName = options.clangFormatLocation;
     CommandLine cmdLine;
     cmdLine.setExecutableLocation(ExecutableLocation(clangProcessName));
-    cmdLine.addArg("--assume-filename=source.cs");
+
+    cmdLine.addArg("--assume-filename");
+    cmdLine.addArg(options.fileName + ".cs");
     if (cursorOffset != -1)
     {
         cmdLine.addArg("--cursor=" + String(cursorOffset));
@@ -133,7 +171,17 @@ List<Edit> formatSource(UnownedStringSlice text, Index lineStart, Index lineEnd,
         cmdLine.addArg("--lines=" + String(lineStart) + ":" + String(lineEnd + 1));
     }
     cmdLine.addArg("--output-replacements-xml");
-    if (options.style.getLength())
+    // clang-format does not allow non-builtin style for `fallback-style`.
+    // We detect if clang format file exists, and if not set style directly to user specified fallback style.
+    if (shouldUseFallbackStyle(options))
+    {
+        if (options.fallbackStyle.getLength())
+        {
+            cmdLine.addArg("-style");
+            cmdLine.addArg(options.fallbackStyle);
+        }
+    }
+    else if (options.style.getLength())
     {
         cmdLine.addArg("-style");
         cmdLine.addArg(options.style);
diff --git a/source/slang/slang-language-server-auto-format.h b/source/slang/slang-language-server-auto-format.h
index b30a2f039..a2668dbe1 100644
--- a/source/slang/slang-language-server-auto-format.h
+++ b/source/slang/slang-language-server-auto-format.h
@@ -22,7 +22,9 @@ enum class FormatBehavior
 struct FormatOptions
 {
     String clangFormatLocation;
-    String style = "{BasedOnStyle: Microsoft}";
+    String style = "file";
+    String fallbackStyle = "{BasedOnStyle: Microsoft}";
+    String fileName;
     bool allowLineBreakInOnTypeFormatting = false;
     bool allowLineBreakInRangeFormatting = false;
     FormatBehavior behavior = FormatBehavior::Standard;
diff --git a/source/slang/slang-language-server.cpp b/source/slang/slang-language-server.cpp
index e2469a88a..bb662db91 100644
--- a/source/slang/slang-language-server.cpp
+++ b/source/slang/slang-language-server.cpp
@@ -167,15 +167,15 @@ SlangResult LanguageServer::parseNextMessage()
                 if (response.result.getKind() == JSONValue::Kind::Array)
                 {
                     auto arr = m_connection->getContainer()->getArray(response.result);
-                    if (arr.getCount() == 11)
+                    if (arr.getCount() == 12)
                     {
                         updatePredefinedMacros(arr[0]);
                         updateSearchPaths(arr[1]);
                         updateSearchInWorkspace(arr[2]);
                         updateCommitCharacters(arr[3]);
-                        updateFormattingOptions(arr[4], arr[5], arr[6], arr[7]);
-                        updateInlayHintOptions(arr[8], arr[9]);
-                        updateTraceOptions(arr[10]);
+                        updateFormattingOptions(arr[4], arr[5], arr[6], arr[7], arr[8]);
+                        updateInlayHintOptions(arr[9], arr[10]);
+                        updateTraceOptions(arr[11]);
                     }
                 }
                 break;
@@ -1149,6 +1149,7 @@ SlangResult LanguageServer::formatting(const LanguageServerProtocol::DocumentFor
     }
     if (m_formatOptions.clangFormatLocation.getLength() == 0)
         m_formatOptions.clangFormatLocation = findClangFormatTool();
+    m_formatOptions.fileName = canonicalPath;
     auto edits = formatSource(doc->getText().getUnownedSlice(), -1, -1, -1, m_formatOptions);
     auto textEdits = translateTextEdits(doc, edits);
     m_connection->sendResult(&textEdits, responseId);
@@ -1332,12 +1333,13 @@ void LanguageServer::updateCommitCharacters(const JSONValue& jsonValue)
     }
 }
 
-void LanguageServer::updateFormattingOptions(const JSONValue& clangFormatLoc, const JSONValue& clangFormatStyle, const JSONValue& allowLineBreakOnType, const JSONValue& allowLineBreakInRange)
+void LanguageServer::updateFormattingOptions(const JSONValue& clangFormatLoc, const JSONValue& clangFormatStyle, const JSONValue& clangFormatFallbackStyle, const JSONValue& allowLineBreakOnType, const JSONValue& allowLineBreakInRange)
 {
     auto container = m_connection->getContainer();
     JSONToNativeConverter converter(container, m_connection->getSink());
     converter.convert(clangFormatLoc, &m_formatOptions.clangFormatLocation);
     converter.convert(clangFormatStyle, &m_formatOptions.style);
+    converter.convert(clangFormatFallbackStyle, &m_formatOptions.fallbackStyle);
     converter.convert(allowLineBreakOnType, &m_formatOptions.allowLineBreakInOnTypeFormatting);
     converter.convert(allowLineBreakInRange, &m_formatOptions.allowLineBreakInRangeFormatting);
     if (m_formatOptions.style.getLength() == 0)
@@ -1396,6 +1398,8 @@ void LanguageServer::sendConfigRequest()
     args.items.add(item);
     item.section = "slang.format.clangFormatStyle";
     args.items.add(item);
+    item.section = "slang.format.clangFormatFallbackStyle";
+    args.items.add(item);
     item.section = "slang.format.allowLineBreakChangesInOnTypeFormatting";
     args.items.add(item);
     item.section = "slang.format.allowLineBreakChangesInRangeFormatting";
diff --git a/source/slang/slang-language-server.h b/source/slang/slang-language-server.h
index e7a5f3244..8ece0cc41 100644
--- a/source/slang/slang-language-server.h
+++ b/source/slang/slang-language-server.h
@@ -141,7 +141,7 @@ private:
     void updateSearchPaths(const JSONValue& value);
     void updateSearchInWorkspace(const JSONValue& value);
     void updateCommitCharacters(const JSONValue& value);
-    void updateFormattingOptions(const JSONValue& clangFormatLoc, const JSONValue& clangFormatStyle, const JSONValue& allowLineBreakOnType, const JSONValue& allowLineBreakInRange);
+    void updateFormattingOptions(const JSONValue& clangFormatLoc, const JSONValue& clangFormatStyle, const JSONValue& clangFormatFallbackStyle, const JSONValue& allowLineBreakOnType, const JSONValue& allowLineBreakInRange);
     void updateInlayHintOptions(const JSONValue& deducedTypes, const JSONValue& parameterNames);
     void updateTraceOptions(const JSONValue& value);