Force a different clang-formatter configuration on autoformat

The configuration is provided just for the time needed for the formatter
to run, afterwards the file is removed. This should not affect users
since the file is created in the temporary folder.

Author: cmaglie

Diff for: handler/handler.go

@@ -411,6 +411,11 @@ func (handler *InoHandler) HandleMessageFromIDE(ctx context.Context, conn *jsonr
 		p.TextDocument, err = handler.ino2cppTextDocumentIdentifier(p.TextDocument)
 		cppURI = p.TextDocument.URI
 		log.Printf("    --> formatting(%s)", p.TextDocument.URI)
+		if cleanup, e := handler.createClangdFormatterConfig(cppURI); e != nil {
+			err = e
+		} else {
+			defer cleanup()
+		}
 
 	case *lsp.DocumentRangeFormattingParams:
 		// Method: "textDocument/rangeFormatting"
@@ -420,6 +425,11 @@ func (handler *InoHandler) HandleMessageFromIDE(ctx context.Context, conn *jsonr
 			params = cppParams
 			cppURI = cppParams.TextDocument.URI
 			log.Printf("    --> %s(%s:%s)", req.Method, cppParams.TextDocument.URI, cppParams.Range)
+			if cleanup, e := handler.createClangdFormatterConfig(cppURI); e != nil {
+				err = e
+			} else {
+				defer cleanup()
+			}
 		} else {
 			err = e
 		}
@@ -1749,6 +1759,29 @@ func (handler *InoHandler) FromClangd(ctx context.Context, connection *jsonrpc2.
 	return result, err
 }
 
+func (handler *InoHandler) createClangdFormatterConfig(cppuri lsp.DocumentURI) (func(), error) {
+	// clangd looks for a .clang-format configuration file on the same directory
+	// pointed by the uri passed in the lsp command parameters.
+	// https://github.com/llvm/llvm-project/blob/64d06ed9c9e0389cd27545d2f6e20455a91d89b1/clang-tools-extra/clangd/ClangdLSPServer.cpp#L856-L868
+	// https://github.com/llvm/llvm-project/blob/64d06ed9c9e0389cd27545d2f6e20455a91d89b1/clang-tools-extra/clangd/ClangdServer.cpp#L402-L404
+
+	config := `
+AllowShortFunctionsOnASingleLine: None
+`
+	targetFile := cppuri.AsPath()
+	if targetFile.IsNotDir() {
+		targetFile = targetFile.Parent()
+	}
+	targetFile = targetFile.Join(".clang-format")
+	cleanup := func() {
+		targetFile.Remove()
+		log.Printf("    formatter config cleaned")
+	}
+	log.Printf("    writing formatter config in: %s", targetFile)
+	err := targetFile.WriteFile([]byte(config))
+	return cleanup, err
+}
+
 func (handler *InoHandler) showMessage(ctx context.Context, msgType lsp.MessageType, message string) {
 	defer streams.CatchAndLogPanic()