Add hover provider

src/main/java/software/amazon/smithy/lsp/SmithyLanguageServer.java

@@ -104,7 +104,7 @@ public CompletableFuture<InitializeResult> initialize(InitializeParams params) {
     capabilities.setDefinitionProvider(true);
     capabilities.setDeclarationProvider(true);
     capabilities.setCompletionProvider(new CompletionOptions(true, null));
-    capabilities.setHoverProvider(false);
+    capabilities.setHoverProvider(true);
 
     return Utils.completableFuture(new InitializeResult(capabilities));
   }
@@ -180,5 +180,4 @@ public CompletableFuture<List<? extends Location>> selectorCommand(SelectorParam
     }
     return CompletableFuture.completedFuture(Collections.emptyList());
   }
-
 }

src/main/java/software/amazon/smithy/lsp/SmithyTextDocumentService.java

@@ -23,6 +23,7 @@
 import java.net.URISyntaxException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -43,8 +44,11 @@
 import org.eclipse.lsp4j.DidCloseTextDocumentParams;
 import org.eclipse.lsp4j.DidOpenTextDocumentParams;
 import org.eclipse.lsp4j.DidSaveTextDocumentParams;
+import org.eclipse.lsp4j.Hover;
+import org.eclipse.lsp4j.HoverParams;
 import org.eclipse.lsp4j.Location;
 import org.eclipse.lsp4j.LocationLink;
+import org.eclipse.lsp4j.MarkupContent;
 import org.eclipse.lsp4j.MessageParams;
 import org.eclipse.lsp4j.MessageType;
 import org.eclipse.lsp4j.Position;
@@ -69,6 +73,7 @@
 import software.amazon.smithy.model.neighbor.Walker;
 import software.amazon.smithy.model.shapes.Shape;
 import software.amazon.smithy.model.shapes.ShapeId;
+import software.amazon.smithy.model.shapes.SmithyIdlModelSerializer;
 import software.amazon.smithy.model.validation.ValidatedResult;
 import software.amazon.smithy.model.validation.ValidationEvent;
 import software.amazon.smithy.utils.SimpleParser;
@@ -374,6 +379,7 @@ private String getLine(List<String> lines, Position position) {
     @Override
     public CompletableFuture<Either<List<? extends Location>, List<? extends LocationLink>>> definition(
             DefinitionParams params) {
+        // TODO More granular error handling
         try {
             // This attempts to return the definition location that corresponds to a position within a text document.
             // First, the position is used to find any shapes in the model that are defined at that location. Next,
@@ -389,21 +395,12 @@ public CompletableFuture<Either<List<? extends Location>, List<? extends Locatio
             if (initialShapeId.isPresent()) {
                 Model model = project.getModel().unwrap();
                 Shape initialShape = model.getShape(initialShapeId.get()).get();
-                // Find the first non-member neighbor shape or trait applied to a member whose name matches the token.
-                Walker shapeWalker = new Walker(NeighborProviderIndex.of(model).getProvider());
-                Optional<ShapeId> target = shapeWalker.walkShapes(initialShape).stream()
-                        .flatMap(shape -> {
-                            if (shape.isMemberShape()) {
-                                return shape.getAllTraits().values().stream()
-                                        .map(trait -> trait.toShapeId());
-                            } else {
-                                return Stream.of(shape.getId());
-                            }
-                        })
-                        .filter(shapeId -> shapeId.getName().equals(found))
-                        .findFirst();
-                // Use location on target, or else default to initial shape.
-                locations = Collections.singletonList(project.getLocations().get(target.orElse(initialShapeId.get())));
+                Optional<Shape> target = getTargetShape(initialShape, found, model);
+
+                // Use location of target shape or default to the location of the initial shape.
+                ShapeId shapeId = target.map(Shape::getId).orElse(initialShapeId.get());
+                Location shapeLocation = project.getLocations().get(shapeId);
+                locations = Collections.singletonList(shapeLocation);
             } else {
                 // If the definition params do not have a matching shape at that location, return locations of all
                 // shapes that match token by shape name. This makes it possible link the shape name in a line
@@ -423,6 +420,73 @@ public CompletableFuture<Either<List<? extends Location>, List<? extends Locatio
         }
     }
 
+    @Override
+    public CompletableFuture<Hover> hover(HoverParams params) {
+        Hover hover = new Hover();
+        MarkupContent content = new MarkupContent();
+        content.setKind("markdown");
+        Optional<ShapeId> initialShapeId = project.getShapeIdFromLocation(params.getTextDocument().getUri(),
+                params.getPosition());
+        Shape shapeToSerialize = null;
+        Model model = project.getModel().unwrap();
+        // TODO More granular error handling
+        try {
+            String token = findToken(params.getTextDocument().getUri(), params.getPosition());
+            LspLog.println("Found token: " + token);
+            if (initialShapeId.isPresent()) {
+                Shape initialShape = model.getShape(initialShapeId.get()).get();
+                Optional<Shape> target = initialShape.asMemberShape()
+                        .map(memberShape -> model.getShape(memberShape.getTarget()))
+                        .orElse(getTargetShape(initialShape, token, model));
+                shapeToSerialize = target.orElse(initialShape);
+            } else {
+                shapeToSerialize = model.shapes()
+                        .filter(shape -> !shape.isMemberShape())
+                        .filter(shape -> shape.getId().getName().equals(token))
+                        .findAny()
+                        .orElse(null);
+            }
+        } catch (Exception e) {
+            LspLog.println("Failed to determine hover content: " + e);
+        }
+
+        // If a shape to serialize has been found, serialize the shape and set the markup content to render
+        if (shapeToSerialize != null) {
+            content.setValue("```smithy\n" + getSerializedShape(shapeToSerialize, model) + "\n```");
+        }
+
+        hover.setContents(content);
+        return Utils.completableFuture(hover);
+    }
+
+    // Finds the first non-member neighbor shape or trait applied to a member whose name matches the token.
+    private Optional<Shape> getTargetShape(Shape initialShape, String token, Model model) {
+        LspLog.println("Finding target of: " + initialShape);
+        Walker shapeWalker = new Walker(NeighborProviderIndex.of(model).getProvider());
+        return shapeWalker.walkShapes(initialShape).stream()
+                .flatMap(shape -> {
+                    if (shape.isMemberShape()) {
+                        return shape.getAllTraits().values().stream()
+                                .map(trait -> trait.toShapeId());
+                    } else {
+                        return Stream.of(shape.getId());
+                    }
+                })
+                .filter(shapeId -> shapeId.getName().equals(token))
+                .map(shapeId -> model.getShape(shapeId).get())
+                .findFirst();
+    }
+
+    private String getSerializedShape(Shape shape, Model model) {
+        SmithyIdlModelSerializer serializer = SmithyIdlModelSerializer.builder()
+                .metadataFilter(key -> false)
+                .shapeFilter(s -> s.getId().equals(shape.getId()))
+                .serializePrelude().build();
+        Map<Path, String> serialized = serializer.serialize(model);
+        Path path = Paths.get(shape.getId().getNamespace() + ".smithy");
+        return serialized.get(path).trim();
+    }
+
     @Override
     public void didChange(DidChangeTextDocumentParams params) {
         File original = fileUri(params.getTextDocument());

src/test/java/software/amazon/smithy/lsp/SmithyLanguageServerTest.java

@@ -37,11 +37,11 @@ public void initializeServer() throws Exception {
         assertTrue(capabilities.getDefinitionProvider().getLeft());
         assertTrue(capabilities.getDeclarationProvider().getLeft());
         assertEquals(new CompletionOptions(true, null), capabilities.getCompletionProvider());
-        assertFalse(capabilities.getHoverProvider().getLeft());
+        assertTrue(capabilities.getHoverProvider().getLeft());
     }
 
     @Test
-    public void initializeWithTemporaryWorkspace() throws Exception {
+    public void initializeWithTemporaryWorkspace() {
         InitializeParams initParams = new InitializeParams();
         SmithyLanguageServer languageServer = new SmithyLanguageServer();
         languageServer.initialize(initParams);