Rascal LSP formatting API and example.

Author: toinehartman

rascal-lsp/src/main/java/org/rascalmpl/vscode/lsp/parametric/ParametricTextDocumentService.java

@@ -58,6 +58,7 @@
 import org.eclipse.lsp4j.DidCloseTextDocumentParams;
 import org.eclipse.lsp4j.DidOpenTextDocumentParams;
 import org.eclipse.lsp4j.DidSaveTextDocumentParams;
+import org.eclipse.lsp4j.DocumentFormattingParams;
 import org.eclipse.lsp4j.DocumentSymbol;
 import org.eclipse.lsp4j.DocumentSymbolParams;
 import org.eclipse.lsp4j.ExecuteCommandOptions;
@@ -69,8 +70,8 @@
 import org.eclipse.lsp4j.InlayHint;
 import org.eclipse.lsp4j.InlayHintKind;
 import org.eclipse.lsp4j.InlayHintParams;
-import org.eclipse.lsp4j.LocationLink;
 import org.eclipse.lsp4j.Location;
+import org.eclipse.lsp4j.LocationLink;
 import org.eclipse.lsp4j.Position;
 import org.eclipse.lsp4j.ReferenceParams;
 import org.eclipse.lsp4j.SemanticTokens;
@@ -83,6 +84,7 @@
 import org.eclipse.lsp4j.TextDocumentIdentifier;
 import org.eclipse.lsp4j.TextDocumentItem;
 import org.eclipse.lsp4j.TextDocumentSyncKind;
+import org.eclipse.lsp4j.TextEdit;
 import org.eclipse.lsp4j.VersionedTextDocumentIdentifier;
 import org.eclipse.lsp4j.jsonrpc.ResponseErrorException;
 import org.eclipse.lsp4j.jsonrpc.messages.Either;
@@ -104,8 +106,8 @@
 import org.rascalmpl.vscode.lsp.uri.FallbackResolver;
 import org.rascalmpl.vscode.lsp.util.CodeActions;
 import org.rascalmpl.vscode.lsp.util.Diagnostics;
-import org.rascalmpl.vscode.lsp.util.FoldingRanges;
 import org.rascalmpl.vscode.lsp.util.DocumentSymbols;
+import org.rascalmpl.vscode.lsp.util.FoldingRanges;
 import org.rascalmpl.vscode.lsp.util.SemanticTokenizer;
 import org.rascalmpl.vscode.lsp.util.Versioned;
 import org.rascalmpl.vscode.lsp.util.concurrent.InterruptibleFuture;
@@ -511,6 +513,17 @@ public CompletableFuture<List<Either<Command, CodeAction>>> codeAction(CodeActio
         return CodeActions.mergeAndConvertCodeActions(this, dedicatedLanguageName, contribs.getName(), quickfixes, codeActions);
     }
 
+    @Override
+    public CompletableFuture<List<? extends TextEdit>> formatting(DocumentFormattingParams params) {
+        logger.debug("formatting: {}", params);
+
+        // convert the `FormattingOptions` map to a `formattingOptions` constructor
+        // call the `formatting` implementation of the relevant language contribution
+        // with the resulting string and the input tree, compute a list of `TextEdit`s to return
+
+        return CompletableFuture.completedFuture(Collections.emptyList());
+    }
+
     private CompletableFuture<IList> computeCodeActions(final ILanguageContributions contribs, final int startLine, final int startColumn, ITree tree) {
         IList focus = TreeSearch.computeFocusList(tree, startLine, startColumn);
 

rascal-lsp/src/main/rascal/library/demo/lang/pico/LanguageServer.rsc

@@ -39,6 +39,8 @@ import ParseTree;
 import util::ParseErrorRecovery;
 import util::Reflective;
 import lang::pico::\syntax::Main;
+import IO;
+import String;
 
 private Tree (str _input, loc _origin) picoParser(bool allowRecovery) {
     return ParseTree::parser(#start[Program], allowRecovery=allowRecovery, filters=allowRecovery ? {createParseErrorFilter(false)} : {});
@@ -57,9 +59,37 @@ set[LanguageService] picoLanguageServer(bool allowRecovery) = {
     execution(picoExecutionService),
     inlayHint(picoInlayHintService),
     definition(picoDefinitionService),
-    codeAction(picoCodeActionService)
+    codeAction(picoCodeActionService),
+    formatting(picoFormattingService)
 };
 
+str picoFormattingService(Tree input, formattingOptions(int tabSize, bool insertSpaces, bool trimTrailingWhiteSpace, bool insertFinalNewLine, bool trimFinalNewLines)) {
+    str formatted = "<input>";
+    str linesep = "\n";
+
+    println("Warning; `tabSize` (<tabSize>) is ignored");
+    if (insertSpaces) {
+        println("Warning; `insertSpaces` is ignored");
+    }
+
+    str trimLineTrailingWs(/^<nonWhiteSpace:.*\S>\s*$/) = nonWhiteSpace;
+    default str trimLineTrailingWs(/^\s*$/) = "";
+
+    if (trimTrailingWhiteSpace) {
+        formatted = intercalate(linesep, [trimLineTrailingWs(l) | l <- split(linesep, formatted)]);
+    }
+
+    if (trimFinalNewLines, /^<textLines:.*[^\n]>\n+$/ := formatted) {
+        formatted = textLines;
+    }
+
+    if (insertFinalNewLine && /\n$/ !:= formatted) {
+        formatted += "\n";
+    }
+
+    return formatted;
+}
+
 set[LanguageService] picoLanguageServer() = picoLanguageServer(false);
 set[LanguageService] picoLanguageServerWithRecovery() = picoLanguageServer(true);
 

rascal-lsp/src/main/rascal/library/util/LanguageServer.rsc

@@ -268,8 +268,19 @@ data LanguageService
     | references    (set[loc] (Focus _focus) referencesService)
     | implementation(set[loc] (Focus _focus) implementationService)
     | codeAction    (list[CodeAction] (Focus _focus) codeActionService)
+    | formatting    (str (Tree _input, FormattingOptions _opts) formattingService)
     ;
 
+data FormattingOptions
+    // If LSP adds more options, add them as keyword arguments for backward compatibility
+    = formattingOptions(
+        int tabSize
+      , bool insertSpaces
+      , bool trimTrailingWhiteSpace
+      , bool insertFinalNewLine
+      , bool trimFinalNewLines
+    );
+
 @deprecated{Backward compatible with ((parsing)).}
 @synopsis{Construct a `parsing` ((LanguageService))}
 LanguageService parser(Parser parser) = parsing(parser);